internal.py

#!/usr/bin/env python

from __future__ import division

import itertools
import time
from collections import OrderedDict, defaultdict
from copy import deepcopy

import networkx as nx
import numpy as np
from numpy.linalg import multi_dot

from geometric.molecule import Elements, Radii
from geometric.nifty import click, commadash, ang2bohr, bohr2ang, logger
from geometric.rotate import get_expmap, get_expmap_der, is_linear


## Some vector calculus functions
def unit_vector(a):
    """
    Vector function: Given a vector a, return the unit vector
    """
    return a / np.linalg.norm(a)

def d_unit_vector(a, ndim=3):
    term1 = np.eye(ndim)/np.linalg.norm(a)
    term2 = np.outer(a, a)/(np.linalg.norm(a)**3)
    answer = term1-term2
    return answer

def d_cross(a, b):
    """
    Given two vectors a and b, return the gradient of the cross product axb w/r.t. a.
    (Note that the answer is independent of a.)
    Derivative is on the first axis.
    """
    d_cross = np.zeros((3, 3), dtype=float)
    for i in range(3):
        ei = np.zeros(3, dtype=float)
        ei[i] = 1.0
        d_cross[i] = np.cross(ei, b)
    return d_cross

def d_cross_ab(a, b, da, db):
    """
    Given two vectors a, b and their derivatives w/r.t. a parameter, return the derivative
    of the cross product
    """
    answer = np.zeros((da.shape[0], 3), dtype=float)
    for i in range(da.shape[0]):
        answer[i] = np.cross(a, db[i]) + np.cross(da[i], b)
    return answer

def ncross(a, b):
    """
    Scalar function: Given vectors a and b, return the norm of the cross product
    """
    cross = np.cross(a, b)
    return np.linalg.norm(cross)

def d_ncross(a, b):
    """
    Return the gradient of the norm of the cross product w/r.t. a
    """
    ncross = np.linalg.norm(np.cross(a, b))
    term1 = a * np.dot(b, b)
    term2 = -b * np.dot(a, b)
    answer = (term1+term2)/ncross
    return answer

def nudot(a, b):
    r"""
    Given two vectors a and b, return the dot product (\hat{a}).b.
    """
    ev = a / np.linalg.norm(a)
    return np.dot(ev, b)
    
def d_nudot(a, b):
    r"""
    Given two vectors a and b, return the gradient of 
    the norm of the dot product (\hat{a}).b w/r.t. a.
    """
    return np.dot(d_unit_vector(a), b)

def ucross(a, b):
    r"""
    Given two vectors a and b, return the cross product (\hat{a})xb.
    """
    ev = a / np.linalg.norm(a)
    return np.cross(ev, b)
    
def d_ucross(a, b):
    r"""
    Given two vectors a and b, return the gradient of 
    the cross product (\hat{a})xb w/r.t. a.
    """
    ev = a / np.linalg.norm(a)
    return np.dot(d_unit_vector(a), d_cross(ev, b))

def nucross(a, b):
    r"""
    Given two vectors a and b, return the norm of the cross product (\hat{a})xb.
    """
    ev = a / np.linalg.norm(a)
    return np.linalg.norm(np.cross(ev, b))
    
def d_nucross(a, b):
    r"""
    Given two vectors a and b, return the gradient of 
    the norm of the cross product (\hat{a})xb w/r.t. a.
    """
    ev = a / np.linalg.norm(a)
    return np.dot(d_unit_vector(a), d_ncross(ev, b))
## End vector calculus functions

def logArray(mat, precision=3, fmt="f"):
    fmt="%% .%i%s" % (precision, fmt)
    if len(mat.shape) == 1:
        for i in range(mat.shape[0]):
            logger.info(fmt % mat[i]),
        print
    elif len(mat.shape) == 2:
        for i in range(mat.shape[0]):
            for j in range(mat.shape[1]):
                logger.info(fmt % mat[i,j]),
            print
    else:
        raise RuntimeError("One or two dimensional arrays only")

class CartesianX(object):
    def __init__(self, a, w=1.0):
        self.a = a
        self.w = w
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        #return "Cartesian-X %i : Weight %.3f" % (self.a+1, self.w)
        return "Cartesian-X %i" % (self.a+1)
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = self.a == other.a
        if eq and self.w != other.w:
            logger.warning("Warning: CartesianX same atoms, different weights (%.4f %.4f)" % (self.w, other.w))
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        return xyz[a][0]*self.w
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        derivatives[self.a][0] = self.w
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2
    
class CartesianY(object):
    def __init__(self, a, w=1.0):
        self.a = a
        self.w = w
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        # return "Cartesian-Y %i : Weight %.3f" % (self.a+1, self.w)
        return "Cartesian-Y %i" % (self.a+1)
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = self.a == other.a
        if eq and self.w != other.w:
            logger.warning("Warning: CartesianY same atoms, different weights (%.4f %.4f)" % (self.w, other.w))
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        return xyz[a][1]*self.w
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        derivatives[self.a][1] = self.w
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2

class CartesianZ(object):
    def __init__(self, a, w=1.0):
        self.a = a
        self.w = w
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        # return "Cartesian-Z %i : Weight %.3f" % (self.a+1, self.w)
        return "Cartesian-Z %i" % (self.a+1)
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = self.a == other.a
        if eq and self.w != other.w:
            logger.warning("Warning: CartesianZ same atoms, different weights (%.4f %.4f)" % (self.w, other.w))
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        return xyz[a][2]*self.w
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        derivatives[self.a][2] = self.w
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2
    
class TranslationX(object):
    def __init__(self, a, w):
        self.a = a
        self.w = w
        assert len(a) == len(w)
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        # return "Translation-X %s : Weights %s" % (' '.join([str(i+1) for i in self.a]), ' '.join(['%.2e' % i for i in self.w]))
        return "Translation-X %s" % (commadash(self.a))
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        if eq and np.sum((self.w-other.w)**2) > 1e-6:
            logger.warning("Warning: TranslationX same atoms, different weights")
            eq = False
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        return np.sum(xyz[a,0]*self.w)
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        for i, a in enumerate(self.a):
            derivatives[a][0] = self.w[i]
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2
    
class TranslationY(object):
    def __init__(self, a, w):
        self.a = a
        self.w = w
        assert len(a) == len(w)
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        # return "Translation-Y %s : Weights %s" % (' '.join([str(i+1) for i in self.a]), ' '.join(['%.2e' % i for i in self.w]))
        return "Translation-Y %s" % (commadash(self.a))
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        if eq and np.sum((self.w-other.w)**2) > 1e-6:
            logger.warning("Warning: TranslationY same atoms, different weights")
            eq = False
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        return np.sum(xyz[a,1]*self.w)
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        for i, a in enumerate(self.a):
            derivatives[a][1] = self.w[i]
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2

class TranslationZ(object):
    def __init__(self, a, w):
        self.a = a
        self.w = w
        assert len(a) == len(w)
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        # return "Translation-Z %s : Weights %s" % (' '.join([str(i+1) for i in self.a]), ' '.join(['%.2e' % i for i in self.w]))
        return "Translation-Z %s" % (commadash(self.a))
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        if eq and np.sum((self.w-other.w)**2) > 1e-6:
            logger.warning("Warning: TranslationZ same atoms, different weights")
            eq = False
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        return np.sum(xyz[a,2]*self.w)
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        for i, a in enumerate(self.a):
            derivatives[a][2] = self.w[i]
        return derivatives
    
    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        return deriv2

class Rotator(object):

    def __init__(self, a, x0):
        self.a = list(tuple(sorted(a)))
        x0 = x0.reshape(-1, 3)
        self.x0 = x0.copy()
        self.stored_valxyz = np.zeros_like(x0)
        self.stored_value = None
        self.stored_derxyz = np.zeros_like(x0)
        self.stored_deriv = None
        self.stored_deriv2xyz = np.zeros_like(x0)
        self.stored_deriv2 = None
        self.stored_norm = 0.0
        # Extra variables to account for the case of linear molecules
        # The reference axis used for computing dummy atom position
        self.e0 = None
        # Dot-squared measures alignment of molecule long axis with reference axis.
        # If molecule becomes parallel with reference axis, coordinates must be reset.
        self.stored_dot2 = 0.0
        # Flag that records linearity of molecule
        self.linear = False

    def reset(self, x0):
        x0 = x0.reshape(-1, 3)
        self.x0 = x0.copy()
        self.stored_valxyz = np.zeros_like(x0)
        self.stored_value = None
        self.stored_derxyz = np.zeros_like(x0)
        self.stored_deriv = None
        self.stored_deriv2xyz = np.zeros_like(x0)
        self.stored_deriv2 = None
        self.stored_norm = 0.0
        self.e0 = None
        self.stored_dot2 = 0.0
        self.linear = False

    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        if eq and np.sum((self.x0-other.x0)**2) > 1e-6:
            logger.warning("Warning: Rotator same atoms, different reference positions")
        return eq

    def __repr__(self):
        return "Rotator %s" % commadash(self.a)

    def __ne__(self, other):
        return not self.__eq__(other)

    def calc_e0(self):
        """
        Compute the reference axis for adding dummy atoms. 
        Only used in the case of linear molecules.

        We first find the Cartesian axis that is "most perpendicular" to the molecular axis.
        Next we take the cross product with the molecular axis to create a perpendicular vector.
        Finally, this perpendicular vector is normalized to make a unit vector.
        """
        ysel = self.x0[self.a, :]
        vy = ysel[-1]-ysel[0]
        ev = vy / np.linalg.norm(vy)
        # Cartesian axes.
        ex = np.array([1.0,0.0,0.0])
        ey = np.array([0.0,1.0,0.0])
        ez = np.array([0.0,0.0,1.0])
        self.e0 = np.cross(vy, [ex, ey, ez][np.argmin([np.dot(i, ev)**2 for i in [ex, ey, ez]])])
        self.e0 /= np.linalg.norm(self.e0)

    def value(self, xyz):
        xyz = xyz.reshape(-1, 3)
        if np.max(np.abs(xyz-self.stored_valxyz)) < 1e-12:
            return self.stored_value
        else:
            xsel = xyz[self.a, :]
            ysel = self.x0[self.a, :]
            xmean = np.mean(xsel,axis=0)
            ymean = np.mean(ysel,axis=0)
            if not self.linear and is_linear(xsel, ysel):
                # print "Setting linear flag for", self
                self.linear = True
            if self.linear:
                # Handle linear molecules.
                vx = xsel[-1]-xsel[0]
                vy = ysel[-1]-ysel[0]
                # Calculate reference axis (if needed)
                if self.e0 is None: self.calc_e0()
                #log.debug(vx)
                ev = vx / np.linalg.norm(vx)
                # Measure alignment of molecular axis with reference axis
                self.stored_dot2 = np.dot(ev, self.e0)**2
                # Dummy atom is located one Bohr from the molecular center, direction
                # given by cross-product of the molecular axis with the reference axis
                xdum = np.cross(vx, self.e0)
                ydum = np.cross(vy, self.e0)
                exdum = xdum / np.linalg.norm(xdum)
                eydum = ydum / np.linalg.norm(ydum)
                xsel = np.vstack((xsel, exdum+xmean))
                ysel = np.vstack((ysel, eydum+ymean))
            answer = get_expmap(xsel, ysel)
            self.stored_norm = np.linalg.norm(answer)
            self.stored_valxyz = xyz.copy()
            self.stored_value = answer.copy()
            return answer

    def derivative(self, xyz):
        xyz = xyz.reshape(-1, 3)
        if np.max(np.abs(xyz-self.stored_derxyz)) < 1e-12:
            return self.stored_deriv
        else:
            xsel = xyz[self.a, :]
            ysel = self.x0[self.a, :]
            xmean = np.mean(xsel,axis=0)
            ymean = np.mean(ysel,axis=0)
            if not self.linear and is_linear(xsel, ysel):
                # print "Setting linear flag for", self
                self.linear = True
            if self.linear:
                vx = xsel[-1]-xsel[0]
                vy = ysel[-1]-ysel[0]
                if self.e0 is None: self.calc_e0()
                xdum = np.cross(vx, self.e0)
                ydum = np.cross(vy, self.e0)
                exdum = xdum / np.linalg.norm(xdum)
                eydum = ydum / np.linalg.norm(ydum)
                xsel = np.vstack((xsel, exdum+xmean))
                ysel = np.vstack((ysel, eydum+ymean))
            deriv_raw = get_expmap_der(xsel, ysel)
            if self.linear:
                # Chain rule is applied to get terms from
                # dummy atom derivatives
                nxdum = np.linalg.norm(xdum)
                dxdum = d_cross(vx, self.e0)
                dnxdum = d_ncross(vx, self.e0)
                # Derivative of dummy atom position w/r.t. molecular axis vector
                dexdum = (dxdum*nxdum - np.outer(dnxdum,xdum))/nxdum**2
                # Here we may compute finite difference derivatives to check
                # h = 1e-6
                # fdxdum = np.zeros((3, 3), dtype=float)
                # for i in range(3):
                #     vx[i] += h
                #     dPlus = np.cross(vx, self.e0)
                #     dPlus /= np.linalg.norm(dPlus)
                #     vx[i] -= 2*h
                #     dMinus = np.cross(vx, self.e0)
                #     dMinus /= np.linalg.norm(dMinus)
                #     vx[i] += h
                #     fdxdum[i] = (dPlus-dMinus)/(2*h)
                # if np.linalg.norm(dexdum - fdxdum) > 1e-6:
                #     print dexdum - fdxdum
                #     raise Exception()
                # Apply terms from chain rule
                deriv_raw[0]  -= np.dot(dexdum, deriv_raw[-1])
                for i in range(len(self.a)):
                    deriv_raw[i]  += np.dot(np.eye(3), deriv_raw[-1])/len(self.a)
                deriv_raw[-2] += np.dot(dexdum, deriv_raw[-1])
                deriv_raw = deriv_raw[:-1]
            derivatives = np.zeros((xyz.shape[0], 3, 3), dtype=float)
            for i, a in enumerate(self.a):
                derivatives[a, :, :] = deriv_raw[i, :, :]
            self.stored_derxyz = xyz.copy()
            self.stored_deriv = derivatives.copy()
            return derivatives
        
    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1, 3)
        if np.max(np.abs(xyz-self.stored_deriv2xyz)) < 1e-12:
            return self.stored_deriv2
        else:
            xsel = xyz[self.a, :]
            ysel = self.x0[self.a, :]
            xmean = np.mean(xsel,axis=0)
            ymean = np.mean(ysel,axis=0)
            if not self.linear and is_linear(xsel, ysel):
                # print "Setting linear flag for", self
                self.linear = True
            if self.linear:
                vx = xsel[-1]-xsel[0]
                vy = ysel[-1]-ysel[0]
                if self.e0 is None: self.calc_e0()
                xdum = np.cross(vx, self.e0)
                ydum = np.cross(vy, self.e0)
                exdum = xdum / np.linalg.norm(xdum)
                eydum = ydum / np.linalg.norm(ydum)
                xsel = np.vstack((xsel, exdum+xmean))
                ysel = np.vstack((ysel, eydum+ymean))
            deriv_raw, deriv2_raw = get_expmap_der(xsel, ysel, second=True)
            if self.linear:
                # Chain rule is applied to get terms from dummy atom derivatives
                def dexdum_(vx_):
                    xdum_ = np.cross(vx_, self.e0)
                    nxdum_ = np.linalg.norm(xdum_)
                    dxdum_ = d_cross(vx_, self.e0)
                    dnxdum_ = d_ncross(vx_, self.e0)
                    dexdum_ = (dxdum_*nxdum_ - np.outer(dnxdum_,xdum_))/nxdum_**2
                    return dexdum_.copy()
                # First indices: elements of vx that are being differentiated w/r.t.
                # Last index: elements of exdum itself
                dexdum = dexdum_(vx)
                dexdum2 = np.zeros((3, 3, 3), dtype=float)
                h = 1.0e-3
                for i in range(3):
                    vx[i] += h
                    dPlus = dexdum_(vx)
                    vx[i] -= 2*h
                    dMinus = dexdum_(vx)
                    vx[i] += h
                    dexdum2[i] = (dPlus-dMinus)/(2*h)
                # Build arrays that contain derivative of dummy atom position
                # w/r.t. real atom positions
                ddum1 = np.zeros((len(self.a), 3, 3), dtype=float)
                ddum1[0] = -dexdum
                ddum1[-1] = dexdum
                for i in range(len(self.a)):
                    ddum1[i] += np.eye(3)/len(self.a)
                ddum2 = np.zeros((len(self.a), 3, len(self.a), 3, 3), dtype=float)
                ddum2[ 0, : , 0, :] =  dexdum2
                ddum2[-1, : , 0, :] = -dexdum2
                ddum2[ 0, :, -1, :] = -dexdum2
                ddum2[-1, :, -1, :] =  dexdum2
                # =====
                # Do not delete - reference codes using loops for chain rule terms
                # for j in range(len(self.a)): # Loop over atom 1
                #     for m in range(3):       # Loop over xyz of atom 1
                #         for k in range(len(self.a)): # Loop over atom 2
                #             for n in range(3):       # Loop over xyz of atom 2
                #                 for i in range(3):   # Loop over elements of exponential map
                #                     for p in range(3): # Loop over xyz of dummy atom
                #                         deriv2_raw[j, m, k, n, i] += deriv2_raw[j, m, -1, p, i] * ddum1[k, n, p]
                #                         deriv2_raw[j, m, k, n, i] += deriv2_raw[-1, p, k, n, i] * ddum1[j, m, p]
                #                         deriv2_raw[j, m, k, n, i] += deriv_raw[-1, p, i] * ddum2[j, m, k, n, p]
                #                         for q in range(3):
                #                             deriv2_raw[j, m, k, n, i] += deriv2_raw[-1, p, -1, q, i] * ddum1[j, m, p] * ddum1[k, n, q]
                # =====
                deriv2_raw[:-1, :, :-1, :] += np.einsum('jmpi,knp->jmkni', deriv2_raw[:-1, :, -1, :, :], ddum1, optimize=True)
                deriv2_raw[:-1, :, :-1, :] += np.einsum('pkni,jmp->jmkni', deriv2_raw[-1, :, :-1, :, :], ddum1, optimize=True)
                deriv2_raw[:-1, :, :-1, :] += np.einsum('pi,jmknp->jmkni', deriv_raw[-1, :, :], ddum2, optimize=True)
                deriv2_raw[:-1, :, :-1, :] += np.einsum('pqi,jmp,knq->jmkni', deriv2_raw[-1, :, -1, :, :], ddum1, ddum1, optimize=True)
                deriv2_raw = deriv2_raw[:-1, :, :-1, :, :]
            second_derivatives = np.zeros((xyz.shape[0], 3, xyz.shape[0], 3, 3), dtype=float)
            for i, a in enumerate(self.a):
                for j, b in enumerate(self.a):
                    second_derivatives[a, :, b, :, :] = deriv2_raw[i, :, j, :, :]
            return second_derivatives
        
class RotationA(object):
    def __init__(self, a, x0, Rotators, w=1.0):
        self.a = tuple(sorted(a))
        self.x0 = x0
        self.w = w
        if self.a not in Rotators:
            Rotators[self.a] = Rotator(self.a, x0)
        self.Rotator = Rotators[self.a]
        self.isAngular = True
        self.isPeriodic = False

    def __repr__(self):
        # return "Rotation-A %s : Weight %.3f" % (' '.join([str(i+1) for i in self.a]), self.w)
        return "Rotation-A %s" % (commadash(self.a))

    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        # if eq and np.sum((self.w-other.w)**2) > 1e-6:
        #     print "Warning: RotationA same atoms, different weights"
        # if eq and np.sum((self.x0-other.x0)**2) > 1e-6:
        #     print "Warning: RotationA same atoms, different reference positions"
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        return self.Rotator.value(xyz)[0]*self.w
        
    def derivative(self, xyz):
        der_all = self.Rotator.derivative(xyz)
        derivatives = der_all[:, :, 0]*self.w
        return derivatives

    def second_derivative(self, xyz):
        deriv2_all = self.Rotator.second_derivative(xyz)
        second_derivatives = deriv2_all[:, :, :, :, 0]*self.w
        return second_derivatives
    
class RotationB(object):
    def __init__(self, a, x0, Rotators, w=1.0):
        self.a = tuple(sorted(a))
        self.x0 = x0
        self.w = w
        if self.a not in Rotators:
            Rotators[self.a] = Rotator(self.a, x0)
        self.Rotator = Rotators[self.a]
        self.isAngular = True
        self.isPeriodic = False

    def __repr__(self):
        # return "Rotation-B %s : Weight %.3f" % (' '.join([str(i+1) for i in self.a]), self.w)
        return "Rotation-B %s" % (commadash(self.a))

    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        # if eq and np.sum((self.w-other.w)**2) > 1e-6:
        #     print "Warning: RotationB same atoms, different weights"
        # if eq and np.sum((self.x0-other.x0)**2) > 1e-6:
        #     print "Warning: RotationB same atoms, different reference positions"
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        return self.Rotator.value(xyz)[1]*self.w
        
    def derivative(self, xyz):
        der_all = self.Rotator.derivative(xyz)
        derivatives = der_all[:, :, 1]*self.w
        return derivatives

    def second_derivative(self, xyz):
        deriv2_all = self.Rotator.second_derivative(xyz)
        second_derivatives = deriv2_all[:, :, :, :, 1]*self.w
        return second_derivatives

class RotationC(object):
    def __init__(self, a, x0, Rotators, w=1.0):
        self.a = tuple(sorted(a))
        self.x0 = x0
        self.w = w
        if self.a not in Rotators:
            Rotators[self.a] = Rotator(self.a, x0)
        self.Rotator = Rotators[self.a]
        self.isAngular = True
        self.isPeriodic = False

    def __repr__(self):
        # return "Rotation-C %s : Weight %.3f" % (' '.join([str(i+1) for i in self.a]), self.w)
        return "Rotation-C %s" % (commadash(self.a))

    def __eq__(self, other):
        if type(self) is not type(other): return False
        eq = set(self.a) == set(other.a)
        # if eq and np.sum((self.w-other.w)**2) > 1e-6:
        #     print "Warning: RotationC same atoms, different weights"
        # if eq and np.sum((self.x0-other.x0)**2) > 1e-6:
        #     print "Warning: RotationC same atoms, different reference positions"
        return eq

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        return self.Rotator.value(xyz)[2]*self.w
        
    def derivative(self, xyz):
        der_all = self.Rotator.derivative(xyz)
        derivatives = der_all[:, :, 2]*self.w
        return derivatives

    def second_derivative(self, xyz):
        deriv2_all = self.Rotator.second_derivative(xyz)
        second_derivatives = deriv2_all[:, :, :, :, 2]*self.w
        return second_derivatives

class Distance(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b
        if a == b:
            raise RuntimeError('a and b must be different')
        self.isAngular = False
        self.isPeriodic = False

    def __repr__(self):
        return "Distance %i-%i" % (self.a+1, self.b+1)
        
    def __eq__(self, other):
        if type(self) is not type(other): return False
        if self.a == other.a:
            if self.b == other.b:
                return True
        if self.a == other.b:
            if self.b == other.a:
                return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        return np.sqrt(np.sum((xyz[a]-xyz[b])**2))
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = self.a
        n = self.b
        u = (xyz[m] - xyz[n]) / np.linalg.norm(xyz[m] - xyz[n])
        derivatives[m, :] = u
        derivatives[n, :] = -u
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        m = self.a
        n = self.b
        l = np.linalg.norm(xyz[m] - xyz[n])
        u = (xyz[m] - xyz[n]) / l
        mtx = (np.outer(u, u) - np.eye(3))/l
        deriv2[m, :, m, :] = -mtx
        deriv2[n, :, n, :] = -mtx
        deriv2[m, :, n, :] = mtx
        deriv2[n, :, m, :] = mtx
        return deriv2
    
class Angle(object):
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c
        self.isAngular = True
        self.isPeriodic = False
        if len({a, b, c}) != 3:
            raise RuntimeError('a, b, and c must be different')

    def __repr__(self):
        return "Angle %i-%i-%i" % (self.a+1, self.b+1, self.c+1)

    def __eq__(self, other):
        if type(self) is not type(other): return False
        if self.b == other.b:
            if self.a == other.a:
                if self.c == other.c:
                    return True
            if self.a == other.c:
                if self.c == other.a:
                    return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        # vector from first atom to central atom
        vector1 = xyz[a] - xyz[b]
        # vector from last atom to central atom
        vector2 = xyz[c] - xyz[b]
        # norm of the two vectors
        norm1 = np.sqrt(np.sum(vector1**2))
        norm2 = np.sqrt(np.sum(vector2**2))
        dot = np.dot(vector1, vector2)
        # Catch the edge case that very rarely this number is -1.
        if dot / (norm1 * norm2) <= -1.0:
            if (np.abs(dot / (norm1 * norm2)) + 1.0) < -1e-6:
                raise RuntimeError('Encountered invalid value in angle')
            return np.pi
        if dot / (norm1 * norm2) >= 1.0:
            if (np.abs(dot / (norm1 * norm2)) - 1.0) > 1e-6:
                raise RuntimeError('Encountered invalid value in angle')
            return 0.0
        return np.arccos(dot / (norm1 * norm2))

    def normal_vector(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        # vector from first atom to central atom
        vector1 = xyz[a] - xyz[b]
        # vector from last atom to central atom
        vector2 = xyz[c] - xyz[b]
        # norm of the two vectors
        norm1 = np.sqrt(np.sum(vector1**2))
        norm2 = np.sqrt(np.sum(vector2**2))
        crs = np.cross(vector1, vector2)
        crs /= np.linalg.norm(crs)
        return crs
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = self.a
        o = self.b
        n = self.c
        # Unit displacement vectors
        u_prime = (xyz[m] - xyz[o])
        u_norm = np.linalg.norm(u_prime)
        v_prime = (xyz[n] - xyz[o])
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        v = v_prime / v_norm
        VECTOR1 = np.array([1, -1, 1]) / np.sqrt(3)
        VECTOR2 = np.array([-1, 1, 1]) / np.sqrt(3)
        if np.linalg.norm(u + v) < 1e-10 or np.linalg.norm(u - v) < 1e-10:
            # if they're parallel
            if ((np.linalg.norm(u + VECTOR1) < 1e-10) or
                    (np.linalg.norm(u - VECTOR2) < 1e-10)):
                # and they're parallel o [1, -1, 1]
                w_prime = np.cross(u, VECTOR2)
            else:
                w_prime = np.cross(u, VECTOR1)
        else:
            w_prime = np.cross(u, v)
        w = w_prime / np.linalg.norm(w_prime)
        term1 = np.cross(u, w) / u_norm
        term2 = np.cross(w, v) / v_norm
        derivatives[m, :] = term1
        derivatives[n, :] = term2
        derivatives[o, :] = -(term1 + term2)
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        m = self.a
        o = self.b
        n = self.c
        # Unit displacement vectors
        u_prime = (xyz[m] - xyz[o])
        u_norm = np.linalg.norm(u_prime)
        v_prime = (xyz[n] - xyz[o])
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        v = v_prime / v_norm
        # Deriv2 derivatives are set to zero in the case of parallel or antiparallel vectors
        if np.linalg.norm(u + v) < 1e-10 or np.linalg.norm(u - v) < 1e-10:
            return deriv2
        # cosine and sine of the bond angle
        cq = np.dot(u, v)
        sq = np.sqrt(1-cq**2)
        uu = np.outer(u, u)
        uv = np.outer(u, v)
        vv = np.outer(v, v)
        de = np.eye(3)
        term1 = (uv + uv.T - (3*uu - de)*cq)/(u_norm**2*sq)
        term2 = (uv + uv.T - (3*vv - de)*cq)/(v_norm**2*sq)
        term3 = (uu + vv - uv*cq   - de)/(u_norm*v_norm*sq)
        term4 = (uu + vv - uv.T*cq - de)/(u_norm*v_norm*sq)
        der1 = self.derivative(xyz)
        def zeta(a_, m_, n_):
            return (int(a_==m_) - int(a_==n_))
        for a in [m, n, o]:
            for b in [m, n, o]:
                deriv2[a, :, b, :] = (zeta(a, m, o)*zeta(b, m, o)*term1
                                      + zeta(a, n, o)*zeta(b, n, o)*term2
                                      + zeta(a, m, o)*zeta(b, n, o)*term3
                                      + zeta(a, n, o)*zeta(b, m, o)*term4
                                      - (cq/sq) * np.outer(der1[a], der1[b]))
        return deriv2

class LinearAngle(object):
    def __init__(self, a, b, c, axis):
        self.a = a
        self.b = b
        self.c = c
        self.axis = axis
        self.isAngular = False
        self.isPeriodic = False
        if len({a, b, c}) != 3:
            raise RuntimeError('a, b, and c must be different')
        self.e0 = None
        self.stored_dot2 = 0.0

    def reset(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        # Unit vector pointing from a to c.
        v = xyz[c] - xyz[a]
        ev = v / np.linalg.norm(v)
        # Cartesian axes.
        ex = np.array([1.0,0.0,0.0])
        ey = np.array([0.0,1.0,0.0])
        ez = np.array([0.0,0.0,1.0])
        self.e0 = [ex, ey, ez][np.argmin([np.dot(i, ev)**2 for i in [ex, ey, ez]])]
        self.stored_dot2 = 0.0

    def __repr__(self):
        return "LinearAngle%s %i-%i-%i" % (["X","Y"][self.axis], self.a+1, self.b+1, self.c+1)

    def __eq__(self, other):
        if not hasattr(other, 'axis'): return False
        if self.axis is not other.axis: return False
        if type(self) is not type(other): return False
        if self.b == other.b:
            if self.a == other.a:
                if self.c == other.c:
                    return True
            if self.a == other.c:
                if self.c == other.a:
                    return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)

    def value(self, xyz):
        """
        This function measures the displacement of the BA and BC unit
        vectors in the linear angle "ABC". The displacements are measured
        along two axes that are perpendicular to the AC unit vector.
        """
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        # Unit vector pointing from a to c.
        v = xyz[c] - xyz[a]
        ev = v / np.linalg.norm(v)
        if self.e0 is None: self.reset(xyz)
        e0 = self.e0
        self.stored_dot2 = np.dot(ev, e0)**2
        # Now make two unit vectors that are perpendicular to this one.
        c1 = np.cross(ev, e0)
        e1 = c1 / np.linalg.norm(c1)
        c2 = np.cross(ev, e1)
        e2 = c2 / np.linalg.norm(c2)
        # BA and BC unit vectors in ABC angle
        vba = xyz[a]-xyz[b]
        eba = vba / np.linalg.norm(vba)
        vbc = xyz[c]-xyz[b]
        ebc = vbc / np.linalg.norm(vbc)
        if self.axis == 0:
            answer = np.dot(eba, e1) + np.dot(ebc, e1)
        else:
            answer = np.dot(eba, e2) + np.dot(ebc, e2)
        return answer

    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        derivatives = np.zeros_like(xyz)
        ## Finite difference derivatives
        ## fderivatives = np.zeros_like(xyz)
        ## h = 1e-6
        ## for u in range(xyz.shape[0]):
        ##     for v in range(3):
        ##         xyz[u, v] += h
        ##         vPlus = self.value(xyz)
        ##         xyz[u, v] -= 2*h
        ##         vMinus = self.value(xyz)
        ##         xyz[u, v] += h
        ##         fderivatives[u, v] = (vPlus-vMinus)/(2*h)
        # Unit vector pointing from a to c.
        v = xyz[c] - xyz[a]
        ev = v / np.linalg.norm(v)
        if self.e0 is None: self.reset(xyz)
        e0 = self.e0
        c1 = np.cross(ev, e0)
        e1 = c1 / np.linalg.norm(c1)
        c2 = np.cross(ev, e1)
        e2 = c2 / np.linalg.norm(c2)
        # BA and BC unit vectors in ABC angle
        vba = xyz[a]-xyz[b]
        eba = vba / np.linalg.norm(vba)
        vbc = xyz[c]-xyz[b]
        ebc = vbc / np.linalg.norm(vbc)
        # Derivative terms
        de0 = np.zeros((3, 3), dtype=float)
        dev = d_unit_vector(v)
        dc1 = d_cross_ab(ev, e0, dev, de0)
        de1 = np.dot(dc1, d_unit_vector(c1))
        dc2 = d_cross_ab(ev, e1, dev, de1)
        de2 = np.dot(dc2, d_unit_vector(c2))
        deba = d_unit_vector(vba)
        debc = d_unit_vector(vbc)
        if self.axis == 0:
            derivatives[a, :] = np.dot(deba, e1) + np.dot(-de1, eba) + np.dot(-de1, ebc)
            derivatives[b, :] = np.dot(-deba, e1) + np.dot(-debc, e1)
            derivatives[c, :] = np.dot(de1, eba) + np.dot(de1, ebc) + np.dot(debc, e1)
        else:
            derivatives[a, :] = np.dot(deba, e2) + np.dot(-de2, eba) + np.dot(-de2, ebc)
            derivatives[b, :] = np.dot(-deba, e2) + np.dot(-debc, e2)
            derivatives[c, :] = np.dot(de2, eba) + np.dot(de2, ebc) + np.dot(debc, e2)
        ## Finite difference derivatives
        ## if np.linalg.norm(derivatives - fderivatives) > 1e-6:
        ##     print np.linalg.norm(derivatives - fderivatives)
        ##     raise Exception()
        return derivatives
    
    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        deriv2 = np.zeros((xyz.shape[0], 3, xyz.shape[0], 3), dtype=float)
        h = 1.0e-3
        for i in range(3):
            for j in range(3):
                ii = [a, b, c][i]
                xyz[ii, j] += h
                FPlus = self.derivative(xyz)
                xyz[ii, j] -= 2*h
                FMinus = self.derivative(xyz)
                xyz[ii, j] += h
                fderiv = (FPlus-FMinus)/(2*h)
                deriv2[ii, j, :, :] = fderiv
        return deriv2
    
class MultiAngle(object):
    def __init__(self, a, b, c):
        if type(a) is int:
            a = (a,)
        if type(c) is int:
            c = (c,)
        self.a = tuple(a)
        self.b = b
        self.c = tuple(c)
        self.isAngular = True
        self.isPeriodic = False
        if len({a, b, c}) != 3:
            raise RuntimeError('a, b, and c must be different')

    def __repr__(self):
        stra = ("("+','.join(["%i" % (i+1) for i in self.a])+")") if len(self.a) > 1 else "%i" % (self.a[0]+1)
        strc = ("("+','.join(["%i" % (i+1) for i in self.c])+")") if len(self.c) > 1 else "%i" % (self.c[0]+1)
        return "%sAngle %s-%i-%s" % ("Multi" if (len(self.a) > 1 or len(self.c) > 1) else "", stra, self.b+1, strc)

    def __eq__(self, other):
        if type(self) is not type(other): return False
        if self.b == other.b:
            if set(self.a) == set(other.a):
                if set(self.c) == set(other.c):
                    return True
            if set(self.a) == set(other.c):
                if set(self.c) == set(other.a):
                    return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        b = self.b
        c = np.array(self.c)
        xyza = np.mean(xyz[a], axis=0)
        xyzc = np.mean(xyz[c], axis=0)
        # vector from first atom to central atom
        vector1 = xyza - xyz[b]
        # vector from last atom to central atom
        vector2 = xyzc - xyz[b]
        # norm of the two vectors
        norm1 = np.sqrt(np.sum(vector1**2))
        norm2 = np.sqrt(np.sum(vector2**2))
        dot = np.dot(vector1, vector2)
        # Catch the edge case that very rarely this number is -1.
        if dot / (norm1 * norm2) <= -1.0:
            if (np.abs(dot / (norm1 * norm2)) + 1.0) < -1e-6:
                raise RuntimeError('Encountered invalid value in angle')
            return np.pi
        return np.arccos(dot / (norm1 * norm2))

    def normal_vector(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        b = self.b
        c = np.array(self.c)
        xyza = np.mean(xyz[a], axis=0)
        xyzc = np.mean(xyz[c], axis=0)
        # vector from first atom to central atom
        vector1 = xyza - xyz[b]
        # vector from last atom to central atom
        vector2 = xyzc - xyz[b]
        # norm of the two vectors
        norm1 = np.sqrt(np.sum(vector1**2))
        norm2 = np.sqrt(np.sum(vector2**2))
        crs = np.cross(vector1, vector2)
        crs /= np.linalg.norm(crs)
        return crs
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = np.array(self.a)
        o = self.b
        n = np.array(self.c)
        xyzm = np.mean(xyz[m], axis=0)
        xyzn = np.mean(xyz[n], axis=0)
        # Unit displacement vectors
        u_prime = (xyzm - xyz[o])
        u_norm = np.linalg.norm(u_prime)
        v_prime = (xyzn - xyz[o])
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        v = v_prime / v_norm
        VECTOR1 = np.array([1, -1, 1]) / np.sqrt(3)
        VECTOR2 = np.array([-1, 1, 1]) / np.sqrt(3)
        if np.linalg.norm(u + v) < 1e-10 or np.linalg.norm(u - v) < 1e-10:
            # if they're parallel
            if ((np.linalg.norm(u + VECTOR1) < 1e-10) or
                    (np.linalg.norm(u - VECTOR2) < 1e-10)):
                # and they're parallel o [1, -1, 1]
                w_prime = np.cross(u, VECTOR2)
            else:
                w_prime = np.cross(u, VECTOR1)
        else:
            w_prime = np.cross(u, v)
        w = w_prime / np.linalg.norm(w_prime)
        term1 = np.cross(u, w) / u_norm
        term2 = np.cross(w, v) / v_norm
        for i in m:
            derivatives[i, :] = term1/len(m)
        for i in n:
            derivatives[i, :] = term2/len(n)
        derivatives[o, :] = -(term1 + term2)
        return derivatives
    
    def second_derivative(self, xyz):
        raise NotImplementedError("Second derivatives have not been implemented for IC type %s" % self.__name__)

class Dihedral(object):
    def __init__(self, a, b, c, d):
        self.a = a
        self.b = b
        self.c = c
        self.d = d
        self.isAngular = True
        self.isPeriodic = True
        if len({a, b, c, d}) != 4:
            raise RuntimeError('a, b, c and d must be different')

    def __repr__(self):
        return "Dihedral %i-%i-%i-%i" % (self.a+1, self.b+1, self.c+1, self.d+1)

    def __eq__(self, other):
        if type(self) is not type(other): return False
        if self.a == other.a:
            if self.b == other.b:
                if self.c == other.c:
                    if self.d == other.d:
                        return True
        if self.a == other.d:
            if self.b == other.c:
                if self.c == other.b:
                    if self.d == other.a:
                        return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        d = self.d
        vec1 = xyz[b] - xyz[a]
        vec2 = xyz[c] - xyz[b]
        vec3 = xyz[d] - xyz[c]
        cross1 = np.cross(vec2, vec3)
        cross2 = np.cross(vec1, vec2)
        arg1 = np.sum(np.multiply(vec1, cross1)) * \
               np.sqrt(np.sum(vec2**2))
        arg2 = np.sum(np.multiply(cross1, cross2))
        answer = np.arctan2(arg1, arg2)
        return answer
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = self.a
        o = self.b
        p = self.c
        n = self.d
        u_prime = (xyz[m] - xyz[o])
        w_prime = (xyz[p] - xyz[o])
        v_prime = (xyz[n] - xyz[p])
        u_norm = np.linalg.norm(u_prime)
        w_norm = np.linalg.norm(w_prime)
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        w = w_prime / w_norm
        v = v_prime / v_norm
        if (1 - np.dot(u, w)**2) < 1e-6:
            term1 = np.cross(u, w) * 0
            term3 = np.cross(u, w) * 0
        else:
            term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
            term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        if (1 - np.dot(v, w)**2) < 1e-6:
            term2 = np.cross(v, w) * 0
            term4 = np.cross(v, w) * 0
        else:
            term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
            term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        # term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
        # term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
        # term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        # term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        derivatives[m, :] = term1
        derivatives[n, :] = -term2
        derivatives[o, :] = -term1 + term3 - term4
        derivatives[p, :] = term2 - term3 + term4
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        deriv2 = np.zeros((xyz.shape[0], xyz.shape[1], xyz.shape[0], xyz.shape[1]))
        m = self.a
        o = self.b
        p = self.c
        n = self.d
        u_prime = (xyz[m] - xyz[o])
        w_prime = (xyz[p] - xyz[o])
        v_prime = (xyz[n] - xyz[p])
        lu = np.linalg.norm(u_prime)
        lw = np.linalg.norm(w_prime)
        lv = np.linalg.norm(v_prime)
        u = u_prime / lu
        w = w_prime / lw
        v = v_prime / lv
        cu = np.dot(u, w)
        su = (1 - np.dot(u, w)**2)**0.5
        su4 = su**4
        cv = np.dot(v, w)
        sv = (1 - np.dot(v, w)**2)**0.5
        sv4 = sv**4
        if su < 1e-6 or sv < 1e-6 : return deriv2
        
        uxw = np.cross(u, w)
        vxw = np.cross(v, w)

        term1 = np.outer(uxw, w*cu - u)/(lu**2*su4)
        term2 = np.outer(vxw, -w*cv + v)/(lv**2*sv4)
        term3 = np.outer(uxw, w - 2*u*cu + w*cu**2)/(2*lu*lw*su4)
        term4 = np.outer(vxw, w - 2*v*cv + w*cv**2)/(2*lv*lw*sv4)
        term5 = np.outer(uxw, u + u*cu**2 - 3*w*cu + w*cu**3)/(2*lw**2*su4)
        term6 = np.outer(vxw,-v - v*cv**2 + 3*w*cv - w*cv**3)/(2*lw**2*sv4)
        term1 += term1.T
        term2 += term2.T
        term3 += term3.T
        term4 += term4.T
        term5 += term5.T
        term6 += term6.T
        def mk_amat(vec):
            amat = np.zeros((3,3))
            for i in range(3):
                for j in range(3):
                    if i == j: continue
                    k = 3 - i - j
                    amat[i, j] = vec[k] * (j-i) * ((-0.5)**np.abs(j-i))
            return amat
        term7 = mk_amat((-w*cu + u)/(lu*lw*su**2))
        term8 = mk_amat(( w*cv - v)/(lv*lw*sv**2))
        def zeta(a_, m_, n_):
            return (int(a_==m_) - int(a_==n_))
        # deriv2_terms = [np.zeros_like(deriv2) for i in range(9)]
        # Accumulate the second derivative
        for a in [m, n, o, p]:
            for b in [m, n, o, p]:
                deriv2[a, :, b, :] = (zeta(a, m, o)*zeta(b, m, o)*term1 +
                                      zeta(a, n, p)*zeta(b, n, p)*term2 +
                                      (zeta(a, m, o)*zeta(b, o, p) + zeta(a, p, o)*zeta(b, o, m))*term3 +
                                      (zeta(a, n, p)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, n, p))*term4 +
                                      zeta(a, o, p)*zeta(b, p, o)*term5 +
                                      zeta(a, p, o)*zeta(b, o, p)*term6)
                if a != b:
                    deriv2[a, :, b, :] += ((zeta(a, m, o)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, o, m))*term7 +
                                           (zeta(a, n, o)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, o, n))*term8)
        return deriv2
                    
        # Accumulate a dictionary of contributions to the second derivatives by term (for debugging)
        #             deriv2_terms[7][a, :, b, :] = (zeta(a, m, o)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, o, m))*term7
        #             deriv2_terms[8][a, :, b, :] = (zeta(a, n, o)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, o, n))*term8
        #         deriv2_terms[1][a, :, b, :] = zeta(a, m, o)*zeta(b, m, o)*term1
        #         deriv2_terms[2][a, :, b, :] = zeta(a, n, p)*zeta(b, n, p)*term2
        #         deriv2_terms[3][a, :, b, :] = (zeta(a, m, o)*zeta(b, o, p) + zeta(a, p, o)*zeta(b, o, m))*term3
        #         deriv2_terms[4][a, :, b, :] = (zeta(a, n, p)*zeta(b, p, o) + zeta(a, p, o)*zeta(b, n, p))*term4
        #         deriv2_terms[5][a, :, b, :] = zeta(a, o, p)*zeta(b, p, o)*term5
        #         deriv2_terms[6][a, :, b, :] = zeta(a, p, o)*zeta(b, o, p)*term6
        # deriv2_terms[0] = deriv2.copy()
        # 
        #=======
        # Term-by-term checking of the second derivative.
        # Produces output such as:
        # 1x1x a:  0.0000 n:  0.0000 e:  0.0000 Terms: NNNNNNNN  0.0000  0.0000 -0.0000 -0.0000 -0.0000 -0.0000  0.0000  0.0000
        # 1x1y a:  0.3337 n:  0.3337 e:  0.0000 Terms: YNNNNNNN  0.3337  0.0000 -0.0000 -0.0000 -0.0000 -0.0000  0.0000  0.0000
        # 1x1z a:  0.0590 n:  0.0590 e: -0.0000 Terms: YNNNNNNN  0.0590  0.0000 -0.0000  0.0000 -0.0000  0.0000  0.0000  0.0000
        # 
        # def printTerm(strin, num):
        #     i = int(strin[0])-1
        #     j = 'xyz'.index(strin[1])
        #     k = int(strin[2])-1
        #     l = 'xyz'.index(strin[3])
        #     ana = deriv2_terms[0][i,j,k,l]
        #     err = ana-num
        #     correct = np.abs(num-ana) < 1e-5
        #     color = '\x1b[92m' if correct else '\x1b[91m'
        #     print('%i%s%i%s a: % .4f n: % .4f e: % .4f Terms: ' % (i+1, 'xyz'[j], k+1, 'xyz'[l], ana, num, err) +
        #           ''.join(["Y" if np.abs(deriv2_terms[m][i,j,k,l]) > 1e-5 else "N" for m in range(1, 9)]) + ' ' +
        #           ' '.join(["%s% .4f\x1b[0m" % (color if np.abs(deriv2_terms[m][i,j,k,l]) > 1e-5 else '',
        #                                         deriv2_terms[m][i,j,k,l]) for m in range(1, 9)]))
        # print("LP checking single term:")
        # printTerm('1x1x',  5.55112e-09)
        # printTerm('1x1y',  3.33702e-01)
        # printTerm('1x1z',  5.90389e-02)

class MultiDihedral(object):
    def __init__(self, a, b, c, d):
        if type(a) is int:
            a = (a, )
        if type(d) is int:
            d = (d, )
        self.a = tuple(a)
        self.b = b
        self.c = c
        self.d = tuple(d)
        self.isAngular = True
        self.isPeriodic = True
        if len({a, b, c, d}) != 4:
            raise RuntimeError('a, b, c and d must be different')

    def __repr__(self):
        stra = ("("+','.join(["%i" % (i+1) for i in self.a])+")") if len(self.a) > 1 else "%i" % (self.a[0]+1)
        strd = ("("+','.join(["%i" % (i+1) for i in self.d])+")") if len(self.d) > 1 else "%i" % (self.d[0]+1)
        return "%sDihedral %s-%i-%i-%s" % ("Multi" if (len(self.a) > 1 or len(self.d) > 1) else "", stra, self.b+1, self.c+1, strd)

    def __eq__(self, other):
        if type(self) is not type(other): return False
        if set(self.a) == set(other.a):
            if self.b == other.b:
                if self.c == other.c:
                    if set(self.d) == set(other.d):
                        return True
        if set(self.a) == set(other.d):
            if self.b == other.c:
                if self.c == other.b:
                    if set(self.d) == set(other.a):
                        return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = np.array(self.a)
        b = self.b
        c = self.c
        d = np.array(self.d)
        xyza = np.mean(xyz[a], axis=0)
        xyzd = np.mean(xyz[d], axis=0)
        
        vec1 = xyz[b] - xyza
        vec2 = xyz[c] - xyz[b]
        vec3 = xyzd - xyz[c]
        cross1 = np.cross(vec2, vec3)
        cross2 = np.cross(vec1, vec2)
        arg1 = np.sum(np.multiply(vec1, cross1)) * \
               np.sqrt(np.sum(vec2**2))
        arg2 = np.sum(np.multiply(cross1, cross2))
        answer = np.arctan2(arg1, arg2)
        return answer
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = np.array(self.a)
        o = self.b
        p = self.c
        n = np.array(self.d)
        xyzm = np.mean(xyz[m], axis=0)
        xyzn = np.mean(xyz[n], axis=0)
        
        u_prime = (xyzm - xyz[o])
        w_prime = (xyz[p] - xyz[o])
        v_prime = (xyzn - xyz[p])
        u_norm = np.linalg.norm(u_prime)
        w_norm = np.linalg.norm(w_prime)
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        w = w_prime / w_norm
        v = v_prime / v_norm
        if (1 - np.dot(u, w)**2) < 1e-6:
            term1 = np.cross(u, w) * 0
            term3 = np.cross(u, w) * 0
        else:
            term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
            term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        if (1 - np.dot(v, w)**2) < 1e-6:
            term2 = np.cross(v, w) * 0
            term4 = np.cross(v, w) * 0
        else:
            term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
            term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        # term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
        # term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
        # term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        # term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        for i in self.a:
            derivatives[i, :] = term1/len(self.a)
        for i in self.d:
            derivatives[i, :] = -term2/len(self.d)
        derivatives[o, :] = -term1 + term3 - term4
        derivatives[p, :] = term2 - term3 + term4
        return derivatives
    
    def second_derivative(self, xyz):
        raise NotImplementedError("Second derivatives have not been implemented for IC type %s" % self.__name__)

class OutOfPlane(object):
    def __init__(self, a, b, c, d):
        self.a = a
        self.b = b
        self.c = c
        self.d = d
        self.isAngular = True
        self.isPeriodic = True
        if len({a, b, c, d}) != 4:
            raise RuntimeError('a, b, c and d must be different')

    def __repr__(self):
        return "Out-of-Plane %i-%i-%i-%i" % (self.a+1, self.b+1, self.c+1, self.d+1)

    def __eq__(self, other):
        if type(self) is not type(other): return False
        if self.a == other.a:
            if {self.b, self.c, self.d} == {other.b, other.c, other.d}:
                if [self.b, self.c, self.d] != [other.b, other.c, other.d]:
                    logger.warning("Warning: OutOfPlane atoms are the same, ordering is different")
                return True
        #     if self.b == other.b:
        #         if self.c == other.c:
        #             if self.d == other.d:
        #                 return True
        # if self.a == other.d:
        #     if self.b == other.c:
        #         if self.c == other.b:
        #             if self.d == other.a:
        #                 return True
        return False

    def __ne__(self, other):
        return not self.__eq__(other)
        
    def value(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        d = self.d
        vec1 = xyz[b] - xyz[a]
        vec2 = xyz[c] - xyz[b]
        vec3 = xyz[d] - xyz[c]
        cross1 = np.cross(vec2, vec3)
        cross2 = np.cross(vec1, vec2)
        arg1 = np.sum(np.multiply(vec1, cross1)) * \
               np.sqrt(np.sum(vec2**2))
        arg2 = np.sum(np.multiply(cross1, cross2))
        answer = np.arctan2(arg1, arg2)
        return answer
        
    def derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        derivatives = np.zeros_like(xyz)
        m = self.a
        o = self.b
        p = self.c
        n = self.d
        u_prime = (xyz[m] - xyz[o])
        w_prime = (xyz[p] - xyz[o])
        v_prime = (xyz[n] - xyz[p])
        u_norm = np.linalg.norm(u_prime)
        w_norm = np.linalg.norm(w_prime)
        v_norm = np.linalg.norm(v_prime)
        u = u_prime / u_norm
        w = w_prime / w_norm
        v = v_prime / v_norm
        if (1 - np.dot(u, w)**2) < 1e-6:
            term1 = np.cross(u, w) * 0
            term3 = np.cross(u, w) * 0
        else:
            term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
            term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        if (1 - np.dot(v, w)**2) < 1e-6:
            term2 = np.cross(v, w) * 0
            term4 = np.cross(v, w) * 0
        else:
            term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
            term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        # term1 = np.cross(u, w) / (u_norm * (1 - np.dot(u, w)**2))
        # term2 = np.cross(v, w) / (v_norm * (1 - np.dot(v, w)**2))
        # term3 = np.cross(u, w) * np.dot(u, w) / (w_norm * (1 - np.dot(u, w)**2))
        # term4 = np.cross(v, w) * np.dot(v, w) / (w_norm * (1 - np.dot(v, w)**2))
        derivatives[m, :] = term1
        derivatives[n, :] = -term2
        derivatives[o, :] = -term1 + term3 - term4
        derivatives[p, :] = term2 - term3 + term4
        return derivatives

    def second_derivative(self, xyz):
        xyz = xyz.reshape(-1,3)
        a = self.a
        b = self.b
        c = self.c
        d = self.d
        deriv2 = np.zeros((xyz.shape[0], 3, xyz.shape[0], 3), dtype=float)
        h = 1.0e-3
        for i in range(4):
            for j in range(3):
                ii = [a, b, c, d][i]
                xyz[ii, j] += h
                FPlus = self.derivative(xyz)
                xyz[ii, j] -= 2*h
                FMinus = self.derivative(xyz)
                xyz[ii, j] += h
                fderiv = (FPlus-FMinus)/(2*h)
                deriv2[ii, j, :, :] = fderiv
        return deriv2
    
CacheWarning = False

class InternalCoordinates(object):
    def __init__(self):
        self.stored_wilsonB = OrderedDict()

    def addConstraint(self, cPrim, cVal):
        raise NotImplementedError("Constraints not supported with Cartesian coordinates")

    def haveConstraints(self):
        raise NotImplementedError("Constraints not supported with Cartesian coordinates")

    def augmentGH(self, xyz, G, H):
        raise NotImplementedError("Constraints not supported with Cartesian coordinates")

    def calcGradProj(self, xyz, gradx):
        raise NotImplementedError("Constraints not supported with Cartesian coordinates")

    def clearCache(self):
        self.stored_wilsonB = OrderedDict()

    def wilsonB(self, xyz):
        """
        Given Cartesian coordinates xyz, return the Wilson B-matrix
        given by dq_i/dx_j where x is flattened (i.e. x1, y1, z1, x2, y2, z2)
        """
        global CacheWarning
        t0 = time.time()
        xhash = hash(xyz.tostring())
        ht = time.time() - t0
        if xhash in self.stored_wilsonB:
            ans = self.stored_wilsonB[xhash]
            return ans
        WilsonB = []
        Der = self.derivatives(xyz)
        for i in range(Der.shape[0]):
            WilsonB.append(Der[i].flatten())
        self.stored_wilsonB[xhash] = np.array(WilsonB)
        if len(self.stored_wilsonB) > 1000 and not CacheWarning:
            logger.warning("\x1b[91mWarning: more than 1000 B-matrices stored, memory leaks likely\x1b[0m")
            CacheWarning = True
        ans = np.array(WilsonB)
        return ans

    def GMatrix(self, xyz):
        """
        Given Cartesian coordinates xyz, return the G-matrix
        given by G = BuBt where u is an arbitrary matrix (default to identity)
        """
        Bmat = self.wilsonB(xyz)
        BuBt = np.dot(Bmat,Bmat.T)
        return BuBt

    def GInverse_SVD(self, xyz):
        xyz = xyz.reshape(-1,3)
        # Perform singular value decomposition
        click()
        loops = 0
        while True:
            try:
                G = self.GMatrix(xyz)
                time_G = click()
                U, S, VT = np.linalg.svd(G)
                time_svd = click()
            except np.linalg.LinAlgError:
                logger.warning("\x1b[1;91m SVD fails, perturbing coordinates and trying again\x1b[0m")
                xyz = xyz + 1e-2*np.random.random(xyz.shape)
                loops += 1
                if loops == 10:
                    raise RuntimeError('SVD failed too many times')
                continue
            break
        # print "Build G: %.3f SVD: %.3f" % (time_G, time_svd),
        V = VT.T
        UT = U.T
        Sinv = np.zeros_like(S)
        LargeVals = 0
        for ival, value in enumerate(S):
            # print "%.5e % .5e" % (ival,value)
            if np.abs(value) > 1e-6:
                LargeVals += 1
                Sinv[ival] = 1/value
        # print "%i atoms; %i/%i singular values are > 1e-6" % (xyz.shape[0], LargeVals, len(S))
        Sinv = np.diag(Sinv)
        Inv = multi_dot([V, Sinv, UT])
        return Inv

    def GInverse_EIG(self, xyz):
        xyz = xyz.reshape(-1,3)
        click()
        G = self.GMatrix(xyz)
        time_G = click()
        Gi = np.linalg.inv(G)
        time_inv = click()
        # print "G-time: %.3f Inv-time: %.3f" % (time_G, time_inv)
        return Gi

    def checkFiniteDifferenceGrad(self, xyz):
        xyz = xyz.reshape(-1,3)
        Analytical = self.derivatives(xyz)
        FiniteDifference = np.zeros_like(Analytical)
        h = 1e-5
        for i in range(xyz.shape[0]):
            for j in range(3):
                x1 = xyz.copy()
                x2 = xyz.copy()
                x1[i,j] += h
                x2[i,j] -= h
                PMDiff = self.calcDiff(x1,x2)
                FiniteDifference[:,i,j] = PMDiff/(2*h)
        logger.info("-=# Now checking first derivatives of internal coordinates w/r.t. Cartesians #=-")
        for i in range(Analytical.shape[0]):
            title = "%20s : %20s" % ("IC %i/%i" % (i+1, Analytical.shape[0]), self.Internals[i])
            lines = [title]
            maxerr = 0.0
            for j in range(Analytical.shape[1]):
                lines.append("Atom %i" % (j+1))
                for k in range(Analytical.shape[2]):
                    error = Analytical[i,j,k] - FiniteDifference[i,j,k]
                    if np.abs(error) > 1e-5:
                        color = "\x1b[91m"
                    else:
                        color = "\x1b[92m"
                    lines.append("%s % .5e % .5e %s% .5e\x1b[0m" % ("xyz"[k], Analytical[i,j,k], FiniteDifference[i,j,k], color, Analytical[i,j,k] - FiniteDifference[i,j,k]))
                    if maxerr < np.abs(error):
                        maxerr = np.abs(error)
            if maxerr > 1e-5:
                logger.info('\n'.join(lines))
            logger.info("%s : Max Error = %.5e" % (title, maxerr))
        logger.info("Finite-difference Finished")
        return FiniteDifference

    def checkFiniteDifferenceHess(self, xyz):
        xyz = xyz.reshape(-1,3)
        Analytical = self.second_derivatives(xyz)
        FiniteDifference = np.zeros_like(Analytical)
        h = 1e-4
        verbose = False
        logger.info("-=# Now checking second derivatives of internal coordinates w/r.t. Cartesians #=-")
        for j in range(xyz.shape[0]):
            for m in range(3):
                for k in range(xyz.shape[0]):
                    for n in range(3):
                        x1 = xyz.copy()
                        x2 = xyz.copy()
                        x3 = xyz.copy()
                        x4 = xyz.copy()
                        x1[j, m] += h
                        x1[k, n] += h # (+, +)
                        x2[j, m] += h
                        x2[k, n] -= h # (+, -)
                        x3[j, m] -= h
                        x3[k, n] += h # (-, +)
                        x4[j, m] -= h
                        x4[k, n] -= h # (-, -)
                        PMDiff1 = self.calcDiff(x1, x2)
                        PMDiff2 = self.calcDiff(x4, x3)
                        FiniteDifference[:, j, m, k, n] += (PMDiff1+PMDiff2)/(4*h**2)
        #                 print('\r%i %i' % (j, k), end='')
        # print()
        for i in range(Analytical.shape[0]):
            title = "%20s : %20s" % ("IC %i/%i" % (i+1, Analytical.shape[0]), self.Internals[i])
            lines = [title]
            if verbose: logger.info(title)
            maxerr = 0.0
            numerr = 0
            for j in range(Analytical.shape[1]):
                for m in range(Analytical.shape[2]):
                    for k in range(Analytical.shape[3]):
                        for n in range(Analytical.shape[4]):
                            ana = Analytical[i,j,m,k,n]
                            fin = FiniteDifference[i,j,m,k,n]
                            error = ana - fin
                            message = "Atom %i %s %i %s a: % 12.5e n: % 12.5e e: % 12.5e %s" % (j+1, 'xyz'[m], k+1, 'xyz'[n], ana, fin,
                                                                                                error, 'X' if np.abs(error)>1e-5 else '')
                            if np.abs(error)>1e-5:
                                numerr += 1
                            if (ana != 0.0 or fin != 0.0) and verbose:
                                logger.info(message)
                            lines.append(message)
                            if maxerr < np.abs(error):
                                maxerr = np.abs(error)
            if maxerr > 1e-5 and not verbose:
                logger.info('\n'.join(lines))
            logger.info("%s : Max Error = % 12.5e (%i above threshold)" % (title, maxerr, numerr))
        logger.info("Finite-difference Finished")
        return FiniteDifference
        
    def calcGrad(self, xyz, gradx):
        q0 = self.calculate(xyz)
        Ginv = self.GInverse(xyz)
        Bmat = self.wilsonB(xyz)
        # Internal coordinate gradient
        # Gq = np.matrix(Ginv)*np.matrix(Bmat)*np.matrix(gradx).T
        Gq = multi_dot([Ginv, Bmat, gradx.T])
        return Gq.flatten()

    def calcHess(self, xyz, gradx, hessx):
        """
        Compute the internal coordinate Hessian. 
        Expects Cartesian coordinates to be provided in a.u.
        """
        xyz = xyz.flatten()
        q0 = self.calculate(xyz)
        Ginv = self.GInverse(xyz)
        Bmat = self.wilsonB(xyz)
        Gq = self.calcGrad(xyz, gradx)
        deriv2 = self.second_derivatives(xyz)
        Bmatp = deriv2.reshape(deriv2.shape[0], xyz.shape[0], xyz.shape[0])
        Hx_BptGq = hessx - np.einsum('pmn,p->mn',Bmatp,Gq)
        Hq = np.einsum('ps,sm,mn,nr,rq', Ginv, Bmat, Hx_BptGq, Bmat.T, Ginv, optimize=True)
        return Hq
    
    def readCache(self, xyz, dQ):
        if not hasattr(self, 'stored_xyz'):
            return None
        xyz = xyz.flatten()
        dQ = dQ.flatten()
        if np.linalg.norm(self.stored_xyz - xyz) < 1e-10:
            if np.linalg.norm(self.stored_dQ - dQ) < 1e-10:
                return self.stored_newxyz
        return None

    def writeCache(self, xyz, dQ, newxyz):
        xyz = xyz.flatten()
        dQ = dQ.flatten()
        newxyz = newxyz.flatten()
        self.stored_xyz = xyz.copy()
        self.stored_dQ = dQ.copy()
        self.stored_newxyz = newxyz.copy()

    def newCartesian(self, xyz, dQ, verbose=True):
        cached = self.readCache(xyz, dQ)
        if cached is not None:
            # print "Returning cached result"
            return cached
        xyz1 = xyz.copy()
        dQ1 = dQ.copy()
        # Iterate until convergence:
        microiter = 0
        ndqs = []
        rmsds = []
        self.bork = False
        # Damping factor
        damp = 1.0
        # Function to exit from loop
        def finish(microiter, rmsdt, ndqt, xyzsave, xyz_iter1):
            if ndqt > 1e-1:
                if verbose: logger.info("Failed to obtain coordinates after %i microiterations (rmsd = %.3e |dQ| = %.3e)" % (microiter, rmsdt, ndqt))
                self.bork = True
                self.writeCache(xyz, dQ, xyz_iter1)
                return xyz_iter1.flatten()
            elif ndqt > 1e-3:
                if verbose: logger.info("Approximate coordinates obtained after %i microiterations (rmsd = %.3e |dQ| = %.3e)" % (microiter, rmsdt, ndqt))
            else:
                if verbose: logger.info("Cartesian coordinates obtained after %i microiterations (rmsd = %.3e |dQ| = %.3e)" % (microiter, rmsdt, ndqt))
            self.writeCache(xyz, dQ, xyzsave)
            return xyzsave.flatten()
        fail_counter = 0
        while True:
            microiter += 1
            Bmat = self.wilsonB(xyz1)
            Ginv = self.GInverse(xyz1)
            # Get new Cartesian coordinates
            dxyz = damp*multi_dot([Bmat.T,Ginv,dQ1.T])
            xyz2 = xyz1 + np.array(dxyz).flatten()
            if microiter == 1:
                xyzsave = xyz2.copy()
                xyz_iter1 = xyz2.copy()
            # Calculate the actual change in internal coordinates
            dQ_actual = self.calcDiff(xyz2, xyz1)
            rmsd = np.sqrt(np.mean((np.array(xyz2-xyz1).flatten())**2))
            ndq = np.linalg.norm(dQ1-dQ_actual)
            if len(ndqs) > 0:
                if ndq > ndqt:
                    if verbose: logger.info("Iter: %i Err-dQ (Best) = %.5e (%.5e) RMSD: %.5e Damp: %.5e (Bad)" % (microiter, ndq, ndqt, rmsd, damp))
                    damp /= 2
                    fail_counter += 1
                    # xyz2 = xyz1.copy()
                else:
                    if verbose: logger.info("Iter: %i Err-dQ (Best) = %.5e (%.5e) RMSD: %.5e Damp: %.5e (Good)" % (microiter, ndq, ndqt, rmsd, damp))
                    fail_counter = 0
                    damp = min(damp*1.2, 1.0)
                    rmsdt = rmsd
                    ndqt = ndq
                    xyzsave = xyz2.copy()
            else:
                if verbose: logger.info("Iter: %i Err-dQ = %.5e RMSD: %.5e Damp: %.5e" % (microiter, ndq, rmsd, damp))
                rmsdt = rmsd
                ndqt = ndq
            ndqs.append(ndq)
            rmsds.append(rmsd)
            # Check convergence / fail criteria
            if rmsd < 1e-6 or ndq < 1e-6:
                return finish(microiter, rmsdt, ndqt, xyzsave, xyz_iter1)
            if fail_counter >= 5:
                return finish(microiter, rmsdt, ndqt, xyzsave, xyz_iter1)
            if microiter == 50:
                return finish(microiter, rmsdt, ndqt, xyzsave, xyz_iter1)
            # Figure out the further change needed
            dQ1 = dQ1 - dQ_actual
            xyz1 = xyz2.copy()
            
class PrimitiveInternalCoordinates(InternalCoordinates):
    def __init__(self, molecule, connect=False, addcart=False, constraints=None, cvals=None, **kwargs):
        super(PrimitiveInternalCoordinates, self).__init__()
        self.connect = connect
        self.addcart = addcart
        self.Internals = []
        self.cPrims = []
        self.cVals = []
        self.Rotators = OrderedDict()
        self.elem = molecule.elem
        for i in range(len(molecule)):
            self.makePrimitives(molecule[i], connect, addcart)
        # Assume we're using the first image for constraints
        self.makeConstraints(molecule[0], constraints, cvals)
        # Reorder primitives for checking with cc's code in TC.
        # Note that reorderPrimitives() _must_ be updated with each new InternalCoordinate class written.
        self.reorderPrimitives()

    def makePrimitives(self, molecule, connect, addcart):
        molecule.build_topology()
        if 'resid' in molecule.Data.keys():
            frags = []
            current_resid = -1
            for i in range(molecule.na):
                if molecule.resid[i] != current_resid:
                    frags.append([i])
                    current_resid = molecule.resid[i]
                else:
                    frags[-1].append(i)
        else:
            frags = [m.nodes() for m in molecule.molecules]
        # coordinates in Angstrom
        coords = molecule.xyzs[0].flatten()
        # Make a distance matrix mapping atom pairs to interatomic distances
        AtomIterator, dxij = molecule.distance_matrix(pbc=False)
        D = {}
        for i, j in zip(AtomIterator, dxij[0]):
            assert i[0] < i[1]
            D[tuple(i)] = j
        dgraph = nx.Graph()
        for i in range(molecule.na):
            dgraph.add_node(i)
        for k, v in D.items():
            dgraph.add_edge(k[0], k[1], weight=v)
        mst = sorted(list(nx.minimum_spanning_edges(dgraph, data=False)))
        # Build a list of noncovalent distances
        noncov = []
        # Connect all non-bonded fragments together
        for edge in mst:
            if edge not in list(molecule.topology.edges()):
                # print "Adding %s from minimum spanning tree" % str(edge)
                if connect:
                    molecule.topology.add_edge(edge[0], edge[1])
                    noncov.append(edge)
        if not connect:
            if addcart:
                for i in range(molecule.na):
                    self.add(CartesianX(i, w=1.0))
                    self.add(CartesianY(i, w=1.0))
                    self.add(CartesianZ(i, w=1.0))
            else:
                for i in frags:
                    if len(i) >= 2:
                        self.add(TranslationX(i, w=np.ones(len(i))/len(i)))
                        self.add(TranslationY(i, w=np.ones(len(i))/len(i)))
                        self.add(TranslationZ(i, w=np.ones(len(i))/len(i)))
                        # Reference coordinates are given in Bohr.
                        sel = coords.reshape(-1,3)[i,:] * ang2bohr
                        sel -= np.mean(sel, axis=0)
                        rg = np.sqrt(np.mean(np.sum(sel**2, axis=1)))
                        self.add(RotationA(i, coords * ang2bohr, self.Rotators, w=rg))
                        self.add(RotationB(i, coords * ang2bohr, self.Rotators, w=rg))
                        self.add(RotationC(i, coords * ang2bohr, self.Rotators, w=rg))
                    else:
                        for j in i:
                            self.add(CartesianX(j, w=1.0))
                            self.add(CartesianY(j, w=1.0))
                            self.add(CartesianZ(j, w=1.0))
        add_tr = False
        if add_tr:
            i = range(molecule.na)
            self.add(TranslationX(i, w=np.ones(len(i))/len(i)))
            self.add(TranslationY(i, w=np.ones(len(i))/len(i)))
            self.add(TranslationZ(i, w=np.ones(len(i))/len(i)))
            # Reference coordinates are given in Bohr.
            sel = coords.reshape(-1,3)[i,:] * ang2bohr
            sel -= np.mean(sel, axis=0)
            rg = np.sqrt(np.mean(np.sum(sel**2, axis=1)))
            self.add(RotationA(i, coords * ang2bohr, self.Rotators, w=rg))
            self.add(RotationB(i, coords * ang2bohr, self.Rotators, w=rg))
            self.add(RotationC(i, coords * ang2bohr, self.Rotators, w=rg))

        # # Build a list of noncovalent distances
        # noncov = []
        # # Connect all non-bonded fragments together
        # while True:
        #     # List of disconnected fragments
        #     subg = list(nx.connected_component_subgraphs(molecule.topology))
        #     # Break out of loop if all fragments are connected
        #     if len(subg) == 1: break
        #     # Find the smallest interatomic distance between any pair of fragments
        #     minD = 1e10
        #     for i in range(len(subg)):
        #         for j in range(i):
        #             for a in subg[i].nodes():
        #                 for b in subg[j].nodes():
        #                     if D[(min(a,b), max(a,b))] < minD:
        #                         minD = D[(min(a,b), max(a,b))]
        #     # Next, create one connection between pairs of fragments that have a
        #     # close-contact distance of at most 1.2 times the minimum found above
        #     for i in range(len(subg)):
        #         for j in range(i):
        #             tminD = 1e10
        #             conn = False
        #             conn_a = None
        #             conn_b = None
        #             for a in subg[i].nodes():
        #                 for b in subg[j].nodes():
        #                     if D[(min(a,b), max(a,b))] < tminD:
        #                         tminD = D[(min(a,b), max(a,b))]
        #                         conn_a = min(a,b)
        #                         conn_b = max(a,b)
        #                     if D[(min(a,b), max(a,b))] <= 1.3*minD:
        #                         conn = True
        #             if conn:
        #                 molecule.topology.add_edge(conn_a, conn_b)
        #                 noncov.append((conn_a, conn_b))

        # Add an internal coordinate for all interatomic distances
        for (a, b) in molecule.topology.edges():
            self.add(Distance(a, b))

        # Add an internal coordinate for all angles
        # LinThre = 0.99619469809174555
        # LinThre = 0.999
        # This number works best for the iron complex
        LinThre = 0.95
        AngDict = defaultdict(list)
        for b in molecule.topology.nodes():
            for a in molecule.topology.neighbors(b):
                for c in molecule.topology.neighbors(b):
                    if a < c:
                        # if (a, c) in molecule.topology.edges() or (c, a) in molecule.topology.edges(): continue
                        Ang = Angle(a, b, c)
                        nnc = (min(a, b), max(a, b)) in noncov
                        nnc += (min(b, c), max(b, c)) in noncov
                        # if nnc >= 2: continue
                        # logger.info("LPW: cosine of angle", a, b, c, "is", np.abs(np.cos(Ang.value(coords))))
                        if np.abs(np.cos(Ang.value(coords))) < LinThre:
                            self.add(Angle(a, b, c))
                            AngDict[b].append(Ang)
                        elif connect or not addcart:
                            # logger.info("Adding linear angle")
                            # Add linear angle IC's
                            # LPW 2019-02-16: Linear angle ICs work well for "very" linear angles in molecules (e.g. HCCCN)
                            # but do not work well for "almost" linear angles in noncovalent systems (e.g. H2O6).
                            # Bringing back old code to use "translations" for the latter case, but should be investigated
                            # more deeply in the future.
                            if nnc == 0:
                                self.add(LinearAngle(a, b, c, 0))
                                self.add(LinearAngle(a, b, c, 1))
                            else:
                                # Unit vector connecting atoms a and c
                                nac = molecule.xyzs[0][c] - molecule.xyzs[0][a]
                                nac /= np.linalg.norm(nac)
                                # Dot products of this vector with the Cartesian axes
                                dots = [np.abs(np.dot(ei, nac)) for ei in np.eye(3)]
                                # Functions for adding Cartesian coordinate
                                # carts = [CartesianX, CartesianY, CartesianZ]
                                trans = [TranslationX, TranslationY, TranslationZ]
                                w = np.array([-1.0, 2.0, -1.0])
                                # Add two of the most perpendicular Cartesian coordinates
                                for i in np.argsort(dots)[:2]:
                                    self.add(trans[i]([a, b, c], w=w))
                            
        for b in molecule.topology.nodes():
            for a in molecule.topology.neighbors(b):
                for c in molecule.topology.neighbors(b):
                    for d in molecule.topology.neighbors(b):
                        if a < c < d:
                            nnc = (min(a, b), max(a, b)) in noncov
                            nnc += (min(b, c), max(b, c)) in noncov
                            nnc += (min(b, d), max(b, d)) in noncov
                            # if nnc >= 1: continue
                            for i, j, k in sorted(list(itertools.permutations([a, c, d], 3))):
                                Ang1 = Angle(b,i,j)
                                Ang2 = Angle(i,j,k)
                                if np.abs(np.cos(Ang1.value(coords))) > LinThre: continue
                                if np.abs(np.cos(Ang2.value(coords))) > LinThre: continue
                                if np.abs(np.dot(Ang1.normal_vector(coords), Ang2.normal_vector(coords))) > LinThre:
                                    self.delete(Angle(i, b, j))
                                    self.add(OutOfPlane(b, i, j, k))
                                    break
                                
        # Find groups of atoms that are in straight lines
        atom_lines = [list(i) for i in molecule.topology.edges()]
        while True:
            # For a line of two atoms (one bond):
            # AB-AC
            # AX-AY
            # i.e. AB is the first one, AC is the second one
            # AX is the second-to-last one, AY is the last one
            # AB-AC-...-AX-AY
            # AB-(AC, AX)-AY
            atom_lines0 = deepcopy(atom_lines)
            for aline in atom_lines:
                # Imagine a line of atoms going like ab-ac-ax-ay.
                # Our job is to extend the line until there are no more
                ab = aline[0]
                ay = aline[-1]
                for aa in molecule.topology.neighbors(ab):
                    if aa not in aline:
                        # If the angle that AA makes with AB and ALL other atoms AC in the line are linear:
                        # Add AA to the front of the list
                        if all([np.abs(np.cos(Angle(aa, ab, ac).value(coords))) > LinThre for ac in aline[1:] if ac != ab]):
                            aline.insert(0, aa)
                for az in molecule.topology.neighbors(ay):
                    if az not in aline:
                        if all([np.abs(np.cos(Angle(ax, ay, az).value(coords))) > LinThre for ax in aline[:-1] if ax != ay]):
                            aline.append(az)
            if atom_lines == atom_lines0: break
        atom_lines_uniq = []
        for i in atom_lines:    # 
            if tuple(i) not in set(atom_lines_uniq):
                atom_lines_uniq.append(tuple(i))
        lthree = [l for l in atom_lines_uniq if len(l) > 2]
        # TODO: Perhaps should reduce the times this is printed out in reaction paths
        # if len(lthree) > 0:
        #     print "Lines of three or more atoms:", ', '.join(['-'.join(["%i" % (i+1) for i in l]) for l in lthree])

        # Normal dihedral code
        for aline in atom_lines_uniq:
            # Go over ALL pairs of atoms in a line
            for (b, c) in itertools.combinations(aline, 2):
                if b > c: (b, c) = (c, b)
                # Go over all neighbors of b
                for a in molecule.topology.neighbors(b):
                    # Go over all neighbors of c
                    for d in molecule.topology.neighbors(c):
                        # Make sure the end-atoms are not in the line and not the same as each other
                        if a not in aline and d not in aline and a != d:
                            nnc = (min(a, b), max(a, b)) in noncov
                            nnc += (min(b, c), max(b, c)) in noncov
                            nnc += (min(c, d), max(c, d)) in noncov
                            # print aline, a, b, c, d
                            Ang1 = Angle(a,b,c)
                            Ang2 = Angle(b,c,d)
                            # Eliminate dihedrals containing angles that are almost linear
                            # (should be eliminated already)
                            if np.abs(np.cos(Ang1.value(coords))) > LinThre: continue
                            if np.abs(np.cos(Ang2.value(coords))) > LinThre: continue
                            self.add(Dihedral(a, b, c, d))
            
        ### Following are codes that evaluate angles and dihedrals involving entire lines-of-atoms
        ### as single degrees of freedom
        ### Unfortunately, they do not seem to improve the performance
        #
        # def pull_lines(a, front=True, middle=False):
        #     """
        #     Given an atom, pull all lines-of-atoms that it is in, e.g.
        #     e.g. 
        #               D
        #               C
        #               B
        #           EFGHAIJKL
        #     returns (B, C, D), (H, G, F, E), (I, J, K, L).
        #   
        #     A is the implicit first item in the list.
        #     Set front to False to make A the implicit last item in the list.
        #     Set middle to True to return lines where A is in the middle e.g. (H, G, F, E) and (I, J, K, L).
        #     """
        #     answer = []
        #     for l in atom_lines_uniq:
        #         if l[0] == a:
        #             answer.append(l[:][1:])
        #         elif l[-1] == a:
        #             answer.append(l[::-1][1:])
        #         elif middle and a in l:
        #             answer.append(l[l.index(a):][1:])
        #             answer.append(l[:l.index(a)][::-1])
        #     if front: return answer
        #     else: return [l[::-1] for l in answer]
        #
        # def same_line(al, bl):
        #     for l in atom_lines_uniq:
        #         if set(al).issubset(set(l)) and set(bl).issubset(set(l)):
        #             return True
        #     return False
        #
        # ## Multiple angle code; does not improve performance for Fe4N system.
        # for b in molecule.topology.nodes():
        #     for al in pull_lines(b, front=False, middle=True):
        #         for cl in pull_lines(b, front=True, middle=True):
        #             if al[0] == cl[-1]: continue
        #             if al[-1] == cl[0]: continue
        #             self.delete(Angle(al[-1], b, cl[0]))
        #             self.delete(Angle(cl[0], b, al[-1]))
        #             if len(set(al).intersection(set(cl))) > 0: continue
        #             if same_line(al, cl):
        #                 continue
        #             if al[-1] < cl[0]:
        #                 self.add(MultiAngle(al, b, cl))
        #             else:
        #                 self.add(MultiAngle(cl[::-1], b, al[::-1]))
        #
        ## Multiple dihedral code
        ## Note: This suffers from a problem where it cannot rebuild the Cartesian coordinates,
        ## possibly due to a bug in the MultiDihedral class.
        # for aline in atom_lines_uniq:
        #     for (b, c) in itertools.combinations(aline, 2):
        #         if b > c: (b, c) = (c, b)
        #         for al in pull_lines(b, front=False, middle=True):
        #             if same_line(al, aline): continue
        #                 # print "Same line:", al, aline
        #             for dl in pull_lines(c, front=True, middle=True):
        #                 if same_line(dl, aline): continue
        #                     # print "Same line:", dl, aline
        #                     # continue
        #                 # if same_line(dl, al): continue
        #                 if al[-1] == dl[0]: continue
        #                 # if len(set(al).intersection(set(dl))) > 0: continue
        #                 # print MultiDihedral(al, b, c, dl)
        #                 self.delete(Dihedral(al[-1], b, c, dl[0]))
        #                 self.add(MultiDihedral(al, b, c, dl))

    def makeConstraints(self, molecule, constraints, cvals):
        # Add the list of constraints. 
        xyz = molecule.xyzs[0].flatten() * ang2bohr
        if constraints is not None:
            if len(constraints) != len(cvals):
                raise RuntimeError("List of constraints should be same length as constraint values")
            for cons, cval in zip(constraints, cvals):
                self.addConstraint(cons, cval, xyz)

    def __repr__(self):
        lines = ["Internal coordinate system (atoms numbered from 1):"]
        typedict = OrderedDict()
        for Internal in self.Internals:
            lines.append(Internal.__repr__())
            if str(type(Internal)) not in typedict:
                typedict[str(type(Internal))] = 1
            else:
                typedict[str(type(Internal))] += 1
        if len(lines) > 100:
            # Print only summary if too many
            lines = []
        for k, v in typedict.items():
            lines.append("%s : %i" % (k, v))
        return '\n'.join(lines)

    def __eq__(self, other):
        answer = True
        for i in self.Internals:
            if i not in other.Internals:
                answer = False
        for i in other.Internals:
            if i not in self.Internals:
                answer = False
        return answer

    def __ne__(self, other):
        return not self.__eq__(other)

    def update(self, other):
        Changed = False
        for i in self.Internals:
            if i not in other.Internals:
                if hasattr(i, 'inactive'):
                    i.inactive += 1
                else:
                    i.inactive = 0
                if i.inactive == 1:
                    logger.info("Deleting:", i)
                    self.Internals.remove(i)
                    Changed = True
            else:
                i.inactive = 0
        for i in other.Internals:
            if i not in self.Internals:
                logger.info("Adding:  ", i)
                self.Internals.append(i)
                Changed = True
        return Changed

    def join(self, other):
        Changed = False
        for i in other.Internals:
            if i not in self.Internals:
                logger.info("Adding:  ", i)
                self.Internals.append(i)
                Changed = True
        return Changed

    def repr_diff(self, other):
        if hasattr(other, 'Prims'):
            output = ['Primitive -> Delocalized']
            otherPrims = other.Prims
        else:
            output = []
            otherPrims = other
        alines = ["-- Added: --"]
        for i in otherPrims.Internals:
            if i not in self.Internals:
                alines.append(i.__repr__())
        dlines = ["-- Deleted: --"]
        for i in self.Internals:
            if i not in otherPrims.Internals:
                dlines.append(i.__repr__())
        if len(alines) > 1:
            output += alines
        if len(dlines) > 1:
            output += dlines
        return '\n'.join(output)

    def resetRotations(self, xyz):
        for Internal in self.Internals:
            if type(Internal) is LinearAngle:
                Internal.reset(xyz)
        for rot in self.Rotators.values():
            rot.reset(xyz)

    def largeRots(self):
        for Internal in self.Internals:
            if type(Internal) is LinearAngle:
                if Internal.stored_dot2 > 0.75:
                    # Linear angle is almost parallel to reference axis
                    return True
            if type(Internal) in [RotationA, RotationB, RotationC]:
                if Internal in self.cPrims:
                    continue
                if Internal.Rotator.stored_norm > 0.9*np.pi:
                    # Molecule has rotated by almost pi
                    return True
                if Internal.Rotator.stored_dot2 > 0.9:
                    # Linear molecule is almost parallel to reference axis
                    return True
        return False

    def calculate(self, xyz):
        answer = []
        for Internal in self.Internals:
            answer.append(Internal.value(xyz))
        return np.array(answer)

    def calculateDegrees(self, xyz):
        answer = []
        for Internal in self.Internals:
            value = Internal.value(xyz)
            if Internal.isAngular:
                value *= 180/np.pi
            answer.append(value)
        return np.array(answer)

    def getRotatorNorms(self):
        rots = []
        for Internal in self.Internals:
            if type(Internal) in [RotationA]:
                rots.append(Internal.Rotator.stored_norm)
        return rots

    def getRotatorDots(self):
        dots = []
        for Internal in self.Internals:
            if type(Internal) in [RotationA]:
                dots.append(Internal.Rotator.stored_dot2)
        return dots

    def printRotations(self, xyz):
        rotNorms = self.getRotatorNorms()
        if len(rotNorms) > 0:
            logger.info("Rotator Norms: " + " ".join(["% .4f" % i for i in rotNorms]))
        rotDots = self.getRotatorDots()
        if len(rotDots) > 0 and np.max(rotDots) > 1e-5:
            logger.info("Rotator Dots : " + " ".join(["% .4f" % i for i in rotDots]))
        linAngs = [ic.value(xyz) for ic in self.Internals if type(ic) is LinearAngle]
        if len(linAngs) > 0:
            logger.info("Linear Angles: " + " ".join(["% .4f" % i for i in linAngs]))

    def derivatives(self, xyz):
        self.calculate(xyz)
        answer = []
        for Internal in self.Internals:
            answer.append(Internal.derivative(xyz))
        # This array has dimensions:
        # 1) Number of internal coordinates
        # 2) Number of atoms
        # 3) 3
        return np.array(answer)

    def second_derivatives(self, xyz):
        self.calculate(xyz)
        answer = []
        for Internal in self.Internals:
            answer.append(Internal.second_derivative(xyz))
        # This array has dimensions:
        # 1) Number of internal coordinates
        # 2) Number of atoms
        # 3) 3
        # 4) Number of atoms
        # 5) 3
        return np.array(answer)
    
    def calcDiff(self, coord1, coord2):
        """ Calculate difference in internal coordinates (coord1-coord2), accounting for changes in 2*pi of angles. """
        Q1 = self.calculate(coord1)
        Q2 = self.calculate(coord2)
        PMDiff = (Q1-Q2)
        for k in range(len(PMDiff)):
            if self.Internals[k].isPeriodic:
                Plus2Pi = PMDiff[k] + 2*np.pi
                Minus2Pi = PMDiff[k] - 2*np.pi
                if np.abs(PMDiff[k]) > np.abs(Plus2Pi):
                    PMDiff[k] = Plus2Pi
                if np.abs(PMDiff[k]) > np.abs(Minus2Pi):
                    PMDiff[k] = Minus2Pi
        return PMDiff

    def GInverse(self, xyz):
        return self.GInverse_SVD(xyz)

    def add(self, dof):
        if dof not in self.Internals:
            self.Internals.append(dof)

    def delete(self, dof):
        for ii in range(len(self.Internals))[::-1]:
            if dof == self.Internals[ii]:
                del self.Internals[ii]

    def addConstraint(self, cPrim, cVal=None, xyz=None):
        if cVal is None and xyz is None:
            raise RuntimeError('Please provide either cval or xyz')
        if cVal is None:
            # If coordinates are provided instead of a constraint value, 
            # then calculate the constraint value from the positions.
            # If both are provided, then the coordinates are ignored.
            cVal = cPrim.value(xyz)
        if cPrim in self.cPrims:
            iPrim = self.cPrims.index(cPrim)
            if np.abs(cVal - self.cVals[iPrim]) > 1e-6:
                logger.info("Updating constraint value to %.4e" % cVal)
            self.cVals[iPrim] = cVal
        else:
            if cPrim not in self.Internals:
                self.Internals.append(cPrim)
            self.cPrims.append(cPrim)
            self.cVals.append(cVal)

    def reorderPrimitives(self):
        # Reorder primitives to be in line with cc's code
        newPrims = []
        for cPrim in self.cPrims:
            newPrims.append(cPrim)
        for typ in [Distance, Angle, LinearAngle, MultiAngle, OutOfPlane, Dihedral, MultiDihedral, CartesianX, CartesianY, CartesianZ, TranslationX, TranslationY, TranslationZ, RotationA, RotationB, RotationC]:
            for p in self.Internals:
                if type(p) is typ and p not in self.cPrims:
                    newPrims.append(p)
        if len(newPrims) != len(self.Internals):
            raise RuntimeError("Not all internal coordinates have been accounted for. You may need to add something to reorderPrimitives()")
        self.Internals = newPrims

    def getConstraints_from(self, other):
        if other.haveConstraints():
            for cPrim, cVal in zip(other.cPrims, other.cVals):
                self.addConstraint(cPrim, cVal)

    def haveConstraints(self):
        return len(self.cPrims) > 0

    def getConstraintViolation(self, xyz):
        nc = len(self.cPrims)
        maxdiff = 0.0
        for ic, c in enumerate(self.cPrims):
            w = c.w if type(c) in [RotationA, RotationB, RotationC] else 1.0
            current = c.value(xyz)/w
            reference = self.cVals[ic]/w
            diff = (current - reference)
            if c.isPeriodic:
                if np.abs(diff-2*np.pi) < np.abs(diff):
                    diff -= 2*np.pi
                if np.abs(diff+2*np.pi) < np.abs(diff):
                    diff += 2*np.pi
            if type(c) in [TranslationX, TranslationY, TranslationZ, CartesianX, CartesianY, CartesianZ, Distance]:
                factor = bohr2ang
            elif c.isAngular:
                factor = 180.0/np.pi
            if np.abs(diff*factor) > maxdiff:
                maxdiff = np.abs(diff*factor)
        return maxdiff
    
    def printConstraints(self, xyz, thre=1e-5):
        nc = len(self.cPrims)
        out_lines = []
        header = "Constraint                         Current      Target       Diff."
        for ic, c in enumerate(self.cPrims):
            w = c.w if type(c) in [RotationA, RotationB, RotationC] else 1.0
            current = c.value(xyz)/w
            reference = self.cVals[ic]/w
            diff = (current - reference)
            if c.isPeriodic:
                if np.abs(diff-2*np.pi) < np.abs(diff):
                    diff -= 2*np.pi
                if np.abs(diff+2*np.pi) < np.abs(diff):
                    diff += 2*np.pi
            if type(c) in [TranslationX, TranslationY, TranslationZ, CartesianX, CartesianY, CartesianZ, Distance]:
                factor = bohr2ang
            elif c.isAngular:
                factor = 180.0/np.pi
            if np.abs(diff*factor) > thre:
                out_lines.append("%-30s  % 10.5f  % 10.5f  % 10.5f" % (str(c), current*factor, reference*factor, diff*factor))
        if len(out_lines) > 0:
            logger.info(header)
            logger.info('\n'.join(out_lines))
            # if type(c) in [RotationA, RotationB, RotationC]:
            #     print c, c.value(xyz)
            #     logArray(c.x0)

    def getConstraintTargetVals(self):
        nc = len(self.cPrims)
        cNames = []
        cVals = []
        for ic, c in enumerate(self.cPrims):
            w = c.w if type(c) in [RotationA, RotationB, RotationC] else 1.0
            reference = self.cVals[ic]/w
            if type(c) in [TranslationX, TranslationY, TranslationZ, CartesianX, CartesianY, CartesianZ, Distance]:
                factor = bohr2ang
            elif c.isAngular:
                factor = 180.0/np.pi
            cNames.append(str(c))
            cVals.append(reference*factor)
        return(cNames, cVals)

    def guess_hessian(self, coords):
        """
        Build a guess Hessian that roughly follows Schlegel's guidelines. 
        """
        xyzs = coords.reshape(-1,3)*bohr2ang
        Hdiag = []
        def covalent(a, b):
            r = np.linalg.norm(xyzs[a]-xyzs[b])
            rcov = Radii[Elements.index(self.elem[a])-1] + Radii[Elements.index(self.elem[b])-1]
            return r/rcov < 1.2
        
        for ic in self.Internals:
            if type(ic) is Distance:
                r = np.linalg.norm(xyzs[ic.a]-xyzs[ic.b]) * ang2bohr
                elem1 = min(Elements.index(self.elem[ic.a]), Elements.index(self.elem[ic.b]))
                elem2 = max(Elements.index(self.elem[ic.a]), Elements.index(self.elem[ic.b]))
                A = 1.734
                if elem1 < 3:
                    if elem2 < 3:
                        B = -0.244
                    elif elem2 < 11:
                        B = 0.352
                    else:
                        B = 0.660
                elif elem1 < 11:
                    if elem2 < 11:
                        B = 1.085
                    else:
                        B = 1.522
                else:
                    B = 2.068
                if covalent(ic.a, ic.b):
                    Hdiag.append(A/(r-B)**3)
                else:
                    Hdiag.append(0.1)
            elif type(ic) in [Angle, LinearAngle, MultiAngle]:
                if type(ic) in [Angle, LinearAngle]:
                    a = ic.a
                    c = ic.c
                else:
                    a = ic.a[-1]
                    c = ic.c[0]
                if min(Elements.index(self.elem[a]),
                       Elements.index(self.elem[ic.b]),
                       Elements.index(self.elem[c])) < 3:
                    A = 0.160
                else:
                    A = 0.250
                if covalent(a, ic.b) and covalent(ic.b, c):
                    Hdiag.append(A)
                else:
                    Hdiag.append(0.1)
            elif type(ic) in [Dihedral, MultiDihedral]:
                r = np.linalg.norm(xyzs[ic.b]-xyzs[ic.c])
                rcov = Radii[Elements.index(self.elem[ic.b])-1] + Radii[Elements.index(self.elem[ic.c])-1]
                # Hdiag.append(0.1)
                Hdiag.append(0.023)
            elif type(ic) is OutOfPlane:
                r1 = xyzs[ic.b]-xyzs[ic.a]
                r2 = xyzs[ic.c]-xyzs[ic.a]
                r3 = xyzs[ic.d]-xyzs[ic.a]
                d = 1 - np.abs(np.dot(r1,np.cross(r2,r3))/np.linalg.norm(r1)/np.linalg.norm(r2)/np.linalg.norm(r3))
                # Hdiag.append(0.1)
                if covalent(ic.a, ic.b) and covalent(ic.a, ic.c) and covalent(ic.a, ic.d):
                    Hdiag.append(0.045)
                else:
                    Hdiag.append(0.023)
            elif type(ic) in [CartesianX, CartesianY, CartesianZ]:
                Hdiag.append(0.05)
            elif type(ic) in [TranslationX, TranslationY, TranslationZ]:
                Hdiag.append(0.05)
            elif type(ic) in [RotationA, RotationB, RotationC]:
                Hdiag.append(0.05)
            else:
                raise RuntimeError('Failed to build guess Hessian matrix. Make sure all IC types are supported')
        return np.diag(Hdiag)

    
class DelocalizedInternalCoordinates(InternalCoordinates):
    def __init__(self, molecule, imagenr=0, build=False, connect=False, addcart=False, constraints=None, cvals=None, remove_tr=False, cart_only=False):
        super(DelocalizedInternalCoordinates, self).__init__()
        # cart_only is just because of how I set up the class structure.
        if cart_only: return
        self.connect = connect
        self.addcart = addcart
        # The DLC contains an instance of primitive internal coordinates.
        self.Prims = PrimitiveInternalCoordinates(molecule, connect=connect, addcart=addcart, constraints=constraints, cvals=cvals)
        self.na = molecule.na
        # Whether constraints have been enforced previously
        self.enforced = False
        self.enforce_fail_printed = False
        # Build the DLC's. This takes some time, so we have the option to turn it off.
        xyz = molecule.xyzs[imagenr].flatten() * ang2bohr
        if build:
            self.build_dlc(xyz)
        if remove_tr:
            self.remove_TR(xyz)

    def clearCache(self):
        super(DelocalizedInternalCoordinates, self).clearCache()
        self.Prims.clearCache()

    def __repr__(self):
        return self.Prims.__repr__()
            
    def update(self, other):
        return self.Prims.update(other.Prims)
        
    def join(self, other):
        return self.Prims.join(other.Prims)
        
    def addConstraint(self, cPrim, cVal, xyz):
        self.Prims.addConstraint(cPrim, cVal, xyz)

    def getConstraints_from(self, other):
        self.Prims.getConstraints_from(other.Prims)
        
    def haveConstraints(self):
        return len(self.Prims.cPrims) > 0

    def getConstraintViolation(self, xyz):
        return self.Prims.getConstraintViolation(xyz)

    def printConstraints(self, xyz, thre=1e-5):
        self.Prims.printConstraints(xyz, thre=thre)

    def getConstraintTargetVals(self):
        return self.Prims.getConstraintTargetVals()

    def augmentGH(self, xyz, G, H):
        """
        Add extra dimensions to the gradient and Hessian corresponding to the constrained degrees of freedom.
        The Hessian becomes:  H  c
                              cT 0
        where the elements of cT are the first derivatives of the constraint function 
        (typically a single primitive minus a constant) with respect to the DLCs. 
        
        Since we picked a DLC to represent the constraint (cProj), we only set one element 
        in each row of cT to be nonzero. Because cProj = a_i * Prim_i + a_j * Prim_j, we have
        d(Prim_c)/d(cProj) = 1.0/a_c where "c" is the index of the primitive being constrained.
        
        The extended elements of the Gradient are equal to the constraint violation.
        
        Parameters
        ----------
        xyz : np.ndarray
            Flat array containing Cartesian coordinates in atomic units
        G : np.ndarray
            Flat array containing internal coordinate gradient
        H : np.ndarray
            Square array containing internal coordinate Hessian

        Returns
        -------
        GC : np.ndarray
            Flat array containing gradient extended by constraint violations
        HC : np.ndarray
            Square matrix extended by partial derivatives d(Prim)/d(cProj)
        """
        # Number of internals (elements of G)
        ni = len(G)
        # Number of constraints
        nc = len(self.Prims.cPrims)
        # Total dimension
        nt = ni+nc
        # Lower block of the augmented Hessian
        cT = np.zeros((nc, ni), dtype=float)
        c0 = np.zeros(nc, dtype=float)
        for ic, c in enumerate(self.Prims.cPrims):
            # Look up the index of the primitive that is being constrained
            iPrim = self.Prims.Internals.index(c)
            # The DLC corresponding to the constrained primitive (a.k.a. cProj) is self.Vecs[self.cDLC[ic]].
            # For a differential change in the DLC, the primitive that we are constraining changes by:
            cT[ic, self.cDLC[ic]] = 1.0/self.Vecs[iPrim, self.cDLC[ic]]
            # Calculate the further change needed in this constrained variable
            c0[ic] = self.Prims.cVals[ic] - c.value(xyz)
            if c.isPeriodic:
                Plus2Pi = c0[ic] + 2*np.pi
                Minus2Pi = c0[ic] - 2*np.pi
                if np.abs(c0[ic]) > np.abs(Plus2Pi):
                    c0[ic] = Plus2Pi
                if np.abs(c0[ic]) > np.abs(Minus2Pi):
                    c0[ic] = Minus2Pi
        # Construct augmented Hessian
        HC = np.zeros((nt, nt), dtype=float)
        HC[0:ni, 0:ni] = H[:,:]
        HC[ni:nt, 0:ni] = cT[:,:]
        HC[0:ni, ni:nt] = cT.T[:,:]
        # Construct augmented gradient
        GC = np.zeros(nt, dtype=float)
        GC[0:ni] = G[:]
        GC[ni:nt] = -c0[:]
        return GC, HC
    
    def applyConstraints(self, xyz):
        """
        Pass in Cartesian coordinates and return new coordinates that satisfy the constraints exactly.
        This is not used in the current constrained optimization code that uses Lagrange multipliers instead.
        """
        xyz1 = xyz.copy()
        niter = 0
        xyzs = []
        ndqs = []
        while True:
            dQ = np.zeros(len(self.Internals), dtype=float)
            for ic, c in enumerate(self.Prims.cPrims):
                # Look up the index of the primitive that is being constrained
                iPrim = self.Prims.Internals.index(c)
                # Look up the index of the DLC that corresponds to the constraint
                iDLC = self.cDLC[ic]
                # Calculate the further change needed in this constrained variable
                dQ[iDLC] = (self.Prims.cVals[ic] - c.value(xyz1))
                if c.isPeriodic:
                    Plus2Pi = dQ[iDLC] + 2*np.pi
                    Minus2Pi = dQ[iDLC] - 2*np.pi
                    if np.abs(dQ[iDLC]) > np.abs(Plus2Pi):
                        dQ[iDLC] = Plus2Pi
                    if np.abs(dQ[iDLC]) > np.abs(Minus2Pi):
                        dQ[iDLC] = Minus2Pi
                dQ[iDLC] /= self.Vecs[iPrim, iDLC]
            xyzs.append(xyz1.copy())
            ndqs.append(np.linalg.norm(dQ))
            # print("applyConstraints calling newCartesian (%i), |dQ| = %.3e" % (niter, np.linalg.norm(dQ)))
            xyz2 = self.newCartesian(xyz1, dQ, verbose=False)
            if np.linalg.norm(dQ) < 1e-6:
                return xyz2
            if niter > 1 and np.linalg.norm(dQ) > np.linalg.norm(dQ0):
                xyz1 = xyzs[np.argmin(ndqs)]
                if not self.enforce_fail_printed:
                    logger.warning("Warning: Failed to enforce exact constraint satisfaction. Please remove possible redundant constraints. See below:")
                    self.printConstraints(xyz1, thre=0.0)
                    self.enforce_fail_printed = True
                return xyz1
            xyz1 = xyz2.copy()
            niter += 1
            dQ0 = dQ.copy()
            
    def newCartesian_withConstraint(self, xyz, dQ, thre=0.1, verbose=False):
        xyz2 = self.newCartesian(xyz, dQ, verbose)
        constraintSmall = len(self.Prims.cPrims) > 0
        for ic, c in enumerate(self.Prims.cPrims):
            w = c.w if type(c) in [RotationA, RotationB, RotationC] else 1.0
            current = c.value(xyz)/w
            reference = self.Prims.cVals[ic]/w
            diff = (current - reference)
            if np.abs(diff-2*np.pi) < np.abs(diff):
                diff -= 2*np.pi
            if np.abs(diff+2*np.pi) < np.abs(diff):
                diff += 2*np.pi
            if np.abs(diff) > thre:
                constraintSmall = False
        if constraintSmall:
            xyz2 = self.applyConstraints(xyz2)
            if not self.enforced:
                logger.info("<<< Enforcing constraint satisfaction >>>")
            self.enforced = True
        else:
            self.enforced = False
        return xyz2
    
    def calcGradProj(self, xyz, gradx):
        """
        Project out the components of the internal coordinate gradient along the
        constrained degrees of freedom. This is used to calculate the convergence
        criteria for constrained optimizations.

        Parameters
        ----------
        xyz : np.ndarray
            Flat array containing Cartesian coordinates in atomic units
        gradx : np.ndarray
            Flat array containing gradient in Cartesian coordinates

        """
        if len(self.Prims.cPrims) == 0:
            return gradx
        q0 = self.calculate(xyz)
        Ginv = self.GInverse(xyz)
        Bmat = self.wilsonB(xyz)
        # Internal coordinate gradient
        # Gq = np.matrix(Ginv)*np.matrix(Bmat)*np.matrix(gradx).T
        Gq = multi_dot([Ginv, Bmat, gradx.T])
        Gqc = np.array(Gq).flatten()
        # Remove the directions that are along the DLCs that we are constraining
        for i in self.cDLC:
            Gqc[i] = 0.0
        # Gxc = np.array(np.matrix(Bmat.T)*np.matrix(Gqc).T).flatten()
        Gxc = multi_dot([Bmat.T, Gqc.T]).flatten()
        return Gxc
    
    def build_dlc(self, xyz):
        """
        Build the delocalized internal coordinates (DLCs) which are linear 
        combinations of the primitive internal coordinates. Each DLC is stored
        as a column in self.Vecs.
        
        In short, each DLC is an eigenvector of the G-matrix, and the number of
        nonzero eigenvalues of G should be equal to 3*N. 
        
        After creating the DLCs, we construct special ones corresponding to primitive
        coordinates that are constrained (cProj).  These are placed in the front (i.e. left)
        of the list of DLCs, and then we perform a Gram-Schmidt orthogonalization.

        This function is called at the end of __init__ after the coordinate system is already
        specified (including which primitives are constraints).

        Parameters
        ----------
        xyz : np.ndarray
            Flat array containing Cartesian coordinates in atomic units
        """
        # Perform singular value decomposition
        click()
        G = self.Prims.GMatrix(xyz)
        # Manipulate G-Matrix to increase weight of constrained coordinates
        if self.haveConstraints():
            for ic, c in enumerate(self.Prims.cPrims):
                iPrim = self.Prims.Internals.index(c)
                G[:, iPrim] *= 1.0
                G[iPrim, :] *= 1.0
        # Water Dimer: 100.0, no check -> -151.1892668451
        time_G = click()
        L, Q = np.linalg.eigh(G)
        time_eig = click()
        # print "Build G: %.3f Eig: %.3f" % (time_G, time_eig)
        LargeVals = 0
        LargeIdx = []
        for ival, value in enumerate(L):
            # print ival, value
            if np.abs(value) > 1e-6:
                LargeVals += 1
                LargeIdx.append(ival)
        Expect = 3*self.na
        # print "%i atoms (expect %i coordinates); %i/%i singular values are > 1e-6" % (self.na, Expect, LargeVals, len(L))
        # if LargeVals <= Expect:
        self.Vecs = Q[:, LargeIdx]
        self.Internals = ["DLC %i" % (i+1) for i in range(len(LargeIdx))]

        # Vecs has number of rows equal to the number of primitives, and
        # number of columns equal to the number of delocalized internal coordinates.
        if self.haveConstraints():
            click()
            # print "Projecting out constraints...",
            V = []
            for ic, c in enumerate(self.Prims.cPrims):
                # Look up the index of the primitive that is being constrained
                iPrim = self.Prims.Internals.index(c)
                # Pick a row out of the eigenvector space. This is a linear combination of the DLCs.
                cVec = self.Vecs[iPrim, :]
                cVec = np.array(cVec)
                cVec /= np.linalg.norm(cVec)
                # This is a "new DLC" that corresponds to the primitive that we are constraining
                cProj = np.dot(self.Vecs,cVec.T)
                cProj /= np.linalg.norm(cProj)
                V.append(np.array(cProj).flatten())
                # print c, cProj[iPrim]
            # V contains the constraint vectors on the left, and the original DLCs on the right
            V = np.hstack((np.array(V).T, np.array(self.Vecs)))
            # Apply Gram-Schmidt to V, and produce U.
            # The Gram-Schmidt process should produce a number of orthogonal DLCs equal to the original number
            thre = 1e-6
            while True:
                U = []
                for iv in range(V.shape[1]):
                    v = V[:, iv].flatten()
                    U.append(v.copy())
                    for ui in U[:-1]:
                        U[-1] -= ui * np.dot(ui, v)
                    if np.linalg.norm(U[-1]) < thre:
                        U = U[:-1]
                        continue
                    U[-1] /= np.linalg.norm(U[-1])
                if len(U) > self.Vecs.shape[1]:
                    thre *= 10
                elif len(U) == self.Vecs.shape[1]:
                    break
                elif len(U) < self.Vecs.shape[1]:
                    raise RuntimeError('Gram-Schmidt orthogonalization has failed (expect %i length %i)' % (self.Vecs.shape[1], len(U)))
            # print "Gram-Schmidt completed with thre=%.0e" % thre
            self.Vecs = np.array(U).T
            # Constrained DLCs are on the left of self.Vecs.
            self.cDLC = [i for i in range(len(self.Prims.cPrims))]

    def remove_TR(self, xyz):
        na = int(len(xyz)/3)
        alla = range(na)
        sel = xyz.reshape(-1,3)
        TRPrims = []
        TRPrims.append(TranslationX(alla, w=np.ones(na)/na))
        TRPrims.append(TranslationY(alla, w=np.ones(na)/na))
        TRPrims.append(TranslationZ(alla, w=np.ones(na)/na))
        sel -= np.mean(sel, axis=0)
        rg = np.sqrt(np.mean(np.sum(sel**2, axis=1)))
        TRPrims.append(RotationA(alla, xyz, self.Prims.Rotators, w=rg))
        TRPrims.append(RotationB(alla, xyz, self.Prims.Rotators, w=rg))
        TRPrims.append(RotationC(alla, xyz, self.Prims.Rotators, w=rg))
        for prim in TRPrims:
            if prim in self.Prims.Internals:
                self.Prims.Internals.remove(prim)
        self.Prims.Internals = TRPrims + self.Prims.Internals
        self.build_dlc(xyz)
        V = []
        for iPrim in range(6):
            # Pick a row out of the eigenvector space. This is a linear combination of the DLCs.
            cVec = self.Vecs[iPrim, :]
            cVec = np.array(cVec)
            cVec /= np.linalg.norm(cVec)
            # This is a "new DLC" that corresponds to the primitive that we are constraining
            cProj = np.dot(self.Vecs,cVec.T)
            cProj /= np.linalg.norm(cProj)
            V.append(np.array(cProj).flatten())
        # V contains the constraint vectors on the left, and the original DLCs on the right
        V = np.hstack((np.array(V).T, np.array(self.Vecs)))
        # Apply Gram-Schmidt to V, and produce U.
        # The Gram-Schmidt process should produce a number of orthogonal DLCs equal to the original number
        thre = 1e-6
        while True:
            U = []
            for iv in range(V.shape[1]):
                v = V[:, iv].flatten()
                U.append(v.copy())
                for ui in U[:-1]:
                    U[-1] -= ui * np.dot(ui, v)
                if np.linalg.norm(U[-1]) < thre:
                    U = U[:-1]
                    continue
                U[-1] /= np.linalg.norm(U[-1])
            if len(U) > self.Vecs.shape[1]:
                thre *= 10
            elif len(U) == self.Vecs.shape[1]:
                break
            elif len(U) < self.Vecs.shape[1]:
                raise RuntimeError('Gram-Schmidt orthogonalization has failed (expect %i length %i)' % (self.Vecs.shape[1], len(U)))
        # print "Gram-Schmidt completed with thre=%.0e" % thre
        self.Vecs = np.array(U).T
        # Constrained DLCs are on the left of self.Vecs.
        # for i, p in enumerate(self.Prims.Internals):
        #     print "%20s" % p,
        #     for j in range(self.Vecs.shape[1]):
        #         print "% .1e" % self.Vecs[i,j],
        #     print
        self.Vecs = self.Vecs[:, 6:]
        self.Internals = ["DLC %i" % (i+1) for i in range(self.Vecs.shape[1])]
        # print "%i coordinates left after removing translation and rotation" % self.Vecs.shape[1]

    def weight_vectors(self, xyz):
        """
        Not used anymore: Multiply each DLC by a constant so that a small displacement along each produces the
        same Cartesian displacement. Otherwise, some DLCs "move by a lot" and others only "move by a little".

        Parameters
        ----------
        xyz : np.ndarray
            Flat array containing Cartesian coordinates in atomic units
        """
        Bmat = self.wilsonB(xyz)
        Ginv = self.GInverse(xyz, None)
        eps = 1e-6
        dxdq = np.zeros(len(self.Internals))
        for i in range(len(self.Internals)):
            dQ = np.zeros(len(self.Internals), dtype=float)
            dQ[i] = eps
            dxyz = multi_dot([Bmat.T, Ginv , dQ.T])
            rmsd = np.sqrt(np.mean(np.sum(np.array(dxyz).reshape(-1,3)**2, axis=1)))
            dxdq[i] = rmsd/eps
        dxdq /= np.max(dxdq)
        for i in range(len(self.Internals)):
            self.Vecs[:, i] *= dxdq[i]

    def __eq__(self, other):
        return self.Prims == other.Prims

    def __ne__(self, other):
        return not self.__eq__(other)

    def largeRots(self):
        """ Determine whether a molecule has rotated by an amount larger than some threshold (hardcoded in Prims.largeRots()). """
        return self.Prims.largeRots()

    def calcDiff(self, coord1, coord2):
        """ Calculate difference in internal coordinates (coord1-coord2), accounting for changes in 2*pi of angles. """
        PMDiff = self.Prims.calcDiff(coord1, coord2)
        Answer = np.dot(PMDiff, self.Vecs)
        return np.array(Answer).flatten()

    def calculate(self, coords):
        """ Calculate the DLCs given the Cartesian coordinates. """
        PrimVals = self.Prims.calculate(coords)
        Answer = np.dot(PrimVals, self.Vecs)
        # To obtain the primitive coordinates from the delocalized internal coordinates,
        # simply multiply self.Vecs*Answer.T where Answer.T is the column vector of delocalized
        # internal coordinates. That means the "c's" in Equation 23 of Schlegel's review paper
        # are simply the rows of the Vecs matrix.
        # print np.dot(np.array(self.Vecs[0,:]).flatten(), np.array(Answer).flatten())
        # print PrimVals[0]
        # raw_input()
        return np.array(Answer).flatten()

    def derivatives(self, coords):
        """ Obtain the change of the DLCs with respect to the Cartesian coordinates. """
        PrimDers = self.Prims.derivatives(coords)
        # The following code does the same as "tensordot"
        # print PrimDers.shape
        # print self.Vecs.shape
        # Answer = np.zeros((self.Vecs.shape[1], PrimDers.shape[1], PrimDers.shape[2]), dtype=float)
        # for i in range(self.Vecs.shape[1]):
        #     for j in range(self.Vecs.shape[0]):
        #         Answer[i, :, :] += self.Vecs[j, i] * PrimDers[j, :, :]
        # print Answer.shape
        Answer1 = np.tensordot(self.Vecs, PrimDers, axes=(0, 0))
        return np.array(Answer1)

    def second_derivatives(self, coords):
        """ Obtain the second derivatives of the DLCs with respect to the Cartesian coordinates. """
        PrimDers = self.Prims.second_derivatives(coords)
        Answer2 = np.tensordot(self.Vecs, PrimDers, axes=(0, 0))
        return np.array(Answer2)
    
    def GInverse(self, xyz):
        return self.GInverse_SVD(xyz)

    def repr_diff(self, other):
        if hasattr(other, 'Prims'):
            return self.Prims.repr_diff(other.Prims)
        else:
            if self.Prims.repr_diff(other) == '':
                return 'Delocalized -> Primitive'
            else:
                return 'Delocalized -> Primitive\n' + self.Prims.repr_diff(other)

    def guess_hessian(self, coords):
        """ Build the guess Hessian, consisting of a diagonal matrix 
        in the primitive space and changed to the basis of DLCs. """
        Hprim = self.Prims.guess_hessian(coords)
        return multi_dot([self.Vecs.T,Hprim,self.Vecs])

    def resetRotations(self, xyz):
        """ Reset the reference geometries for calculating the orientational variables. """
        self.Prims.resetRotations(xyz)

class CartesianCoordinates(PrimitiveInternalCoordinates):
    """
    Cartesian coordinate system, written as a kind of internal coordinate class.  
    This one does not support constraints, because that requires adding some 
    primitive internal coordinates.
    """
    def __init__(self, molecule, **kwargs):
        super(CartesianCoordinates, self).__init__(molecule)
        self.Internals = []
        self.cPrims = []
        self.cVals = []
        self.elem = molecule.elem
        for i in range(molecule.na):
            self.add(CartesianX(i, w=1.0))
            self.add(CartesianY(i, w=1.0))
            self.add(CartesianZ(i, w=1.0))
        if 'constraints' in kwargs and kwargs['constraints'] is not None:
            raise RuntimeError('Do not use constraints with Cartesian coordinates')

    def guess_hessian(self, xyz):
        return 0.5*np.eye(len(xyz.flatten()))