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/*
* Author: Chris Wailes <chris.wailes@gmail.com>
* Project: Parallel Linear Program Solver
* Date: 2011/10/16
* Description: Functions for manipulating dictionaries.
*/

// Standard Incldues
#include <limits.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

// Project Includes
#include "dictionary.h"
#include "kernels.h"
#include "matrix.h"
#include "util.h"

// Constants

#define EXPAND_SIZE 10

// Globals

extern config_t cfg;

// Functions

void dict_add_aux_vars(dict_t* dict, iset_t iset) {
uint col_index, index;
int label;

col_index = dict->num_vars - dict->num_aux_vars;
label = col_index - dict->num_split_vars + dict->num_cons;

for (index = 0; index < iset.size; ++index) {
dict->col_labels[col_index] = ++label;

dict->col_bounds.upper[col_index] = ABS(iset.rows[index].amount);
dict->col_bounds.lower[col_index] = 0.0;
dict->col_rests[col_index] = UPPER;

dict->objective[col_index] = -1.0;

matrix_set_value(&dict->matrix, iset.rows[index].index, col_index, iset.rows[index].amount < 0 ? -1 : 1);

++col_index;
}


free(iset.rows);
}

void dict_add_split_vars(dict_t* dict, uvars_t uvars) {
uint col_index0, col_index1, index, row_index;

col_index1 = dict->num_vars - dict->num_aux_vars - dict->num_split_vars;

for (index = 0; index < uvars.size; ++index) {
col_index0 = uvars.indices[index];
uvars.indices[index] = dict->col_labels[col_index0];

// Set the lower bound of x_i^+ to 0.
dict->col_bounds.lower[col_index0] = 0;
dict->col_rests[col_index0] = LOWER;

// Add the variable x_i^-.
dict->col_labels[col_index1] = -uvars.indices[index];
dict->col_bounds.upper[col_index1] = 0;
dict->col_bounds.lower[col_index1] = -INFINITY;
dict->col_rests[col_index1] = UPPER;
dict->objective[col_index1] = dict->objective[col_index0];

for (row_index = dict->num_cons; row_index-- > 0;) {
matrix_set_value(&dict->matrix, row_index, col_index1, matrix_get_value(&dict->matrix, row_index, col_index0));
}

++col_index1;
}

dict->split_vars = uvars.indices;
}

dict_t* dict_clone(dict_t* orig) {
dict_t* clone;

clone = dict_new(orig->num_vars, orig->num_cons);
dict_copy(clone, orig);

return clone;
}

void dict_copy(dict_t* new_dict, dict_t* orig_dict) {
uint row_index;

// Copy the matrix.
for (row_index = orig_dict->num_cons; row_index-- > 0;) {
memcpy(matrix_get_address(&new_dict->matrix, row_index, 0), matrix_get_address(&orig_dict->matrix, row_index, 0), orig_dict->num_vars * sizeof(double));
}

// Copy the labels.
memcpy(new_dict->col_labels, orig_dict->col_labels, orig_dict->num_vars * sizeof(int));
memcpy(new_dict->row_labels, orig_dict->row_labels, orig_dict->num_cons * sizeof(int));

// Copy the bounds.
memcpy(new_dict->col_bounds.upper, orig_dict->col_bounds.upper, orig_dict->num_vars * sizeof(double));
memcpy(new_dict->col_bounds.lower, orig_dict->col_bounds.lower, orig_dict->num_vars * sizeof(double));

memcpy(new_dict->col_rests, orig_dict->col_rests, orig_dict->num_vars * sizeof(rest_t));

memcpy(new_dict->row_bounds.upper, orig_dict->row_bounds.upper, orig_dict->num_cons * sizeof(double));
memcpy(new_dict->row_bounds.lower, orig_dict->row_bounds.lower, orig_dict->num_cons * sizeof(double));

// Copy the objective.
memcpy(new_dict->objective, orig_dict->objective, orig_dict->num_vars * sizeof(double));
}

void dict_flip_rest(dict_t* dict, uint var_index, rest_t new_rest) {
uint row_index;
double adj_amount;

if (new_rest == UPPER) {
adj_amount = dict->col_bounds.upper[var_index] - dict->col_bounds.lower[var_index];

} else {
adj_amount = dict->col_bounds.lower[var_index] - dict->col_bounds.upper[var_index];
}

// Adjust the row values.
for (row_index = dict->num_cons; row_index-- > 0;) {
dict->row_values[row_index] += matrix_get_value(&dict->matrix, row_index, var_index) * adj_amount;
}

// Adjust the objetive value.
dict->objective_value += dict->objective[var_index] * adj_amount;

// Actually flip the resting bound.
dict->col_rests[var_index] = new_rest;
}

void dict_free(dict_t* dict) {

if (dict == NULL) return;

free(dict->objective);
free(dict->row_values);

matrix_free(&dict->matrix);

free(dict->col_labels);
free(dict->row_labels);

free(dict->row_bounds.upper);
free(dict->row_bounds.lower);
free(dict->col_bounds.upper);
free(dict->col_bounds.lower);

free(dict->col_rests);

free(dict->split_vars);

free(dict);
}

/*
* FIXME: This could possibly be made faster by obtaining a reference to the
* relvent row and then indexing into it, as opposed to re-calculating
* the row pointer each time. However, I do believe that inlining and
* common sub-expression elimination should take care of that for us.
*/
double dict_get_constraint_value(const dict_t* dict, uint con_index) {
uint col_index;
double con_val = 0;

for (col_index = dict->num_vars; col_index-- > 0;) {
con_val += matrix_get_value(&dict->matrix, con_index, col_index) * dict_get_var_bound_value(dict, col_index);
}

return con_val;
}

iset_t dict_get_infeasible_rows(const dict_t* dict) {
uint row_index;
double con_val;

iset_t iset;

iset.size = 0;
iset.rows = calloc(EXPAND_SIZE, sizeof(irow_t));

for (row_index = dict->num_cons; row_index-- > 0;) {
con_val = dict->row_values[row_index];

if (!dict_row_is_feasible(dict, row_index)) {
// Allocate more space if we have run out in the iset struct.
if ((iset.size % EXPAND_SIZE)) {
iset.rows = realloc(iset.rows, (iset.size + EXPAND_SIZE) * sizeof(irow_t));
}

iset.rows[iset.size ].index = row_index;
iset.rows[iset.size++].amount = (con_val < dict->row_bounds.lower[row_index] ? dict->row_bounds.lower : dict->row_bounds.upper)[row_index] - con_val;
}
}

iset.rows = realloc(iset.rows, iset.size * sizeof(irow_t));

return iset;
}

uvars_t dict_get_unbounded_vars(const dict_t* dict) {
uint col_index;
uvars_t uvars;

uvars.size = 0;
uvars.indices = calloc(EXPAND_SIZE, sizeof(uint));

for (col_index = dict->num_vars; col_index-- > 0;) {
if (dict_var_is_unbounded(dict, col_index)) {
// Allocate more space if we have run out in the uvars struct.
if ((uvars.size % EXPAND_SIZE) == 0) {
uvars.indices = realloc(uvars.indices, (uvars.size + EXPAND_SIZE) * sizeof(uint));
}

uvars.indices[uvars.size++] = col_index;
}
}

uvars.indices = realloc(uvars.indices, uvars.size * sizeof(int));

return uvars;
}

inline double dict_get_var_bound_value(const dict_t* dict, uint var_index) {
return (dict->col_rests[var_index] == UPPER ? dict->col_bounds.upper : dict->col_bounds.lower)[var_index];
}

double dict_get_var_value_by_label(const dict_t* dict, uint var_label) {
uint col_index, row_index;
double var_total;

for (col_index = dict->num_vars; col_index-- > 0;) {
if (dict->col_labels[col_index] == var_label) {

var_total = dict_get_var_bound_value(dict, col_index);

if (dict_var_was_split(dict, var_label)) {
var_total -= dict_get_var_value_by_label(dict, -var_label);
}

return var_total;
}
}

for (row_index = dict->num_cons; row_index-- > 0;) {
if (dict->row_labels[row_index] == var_label) {

var_total = dict->row_values[row_index];

if (dict_var_was_split(dict, var_label)) {
var_total -= dict_get_var_value_by_label(dict, -var_label);
}

return var_total;
}
}

fprintf(stderr, "Unknown variable request: x%u\n", var_label);
exit(-1);
}

bool dict_init(dict_t** dict) {
uint col_index, row_index;
uint last_orig_var_label;

uvars_t uvars;
iset_t iset;

dict_t* stage1_dict;
dict_t* stage2_dict;
dict_t* orig_dict = *dict;

uvars = dict_get_unbounded_vars(orig_dict);

if (uvars.size == 0) {
stage1_dict = orig_dict;
orig_dict = NULL;

} else {
/*
* Allocate a new dictionary with enough space for the split
* variables.
*/
stage1_dict = dict_new(orig_dict->num_vars + uvars.size, orig_dict->num_cons);
stage1_dict->num_aux_vars = 0;
stage1_dict->num_split_vars = uvars.size;

// Copy the original dictionary into the stage 1 dictionary.
dict_copy(stage1_dict, orig_dict);

// Add the split variables.
dict_add_split_vars(stage1_dict, uvars);

/*
* Set the bounds and values now that we don't have a column resting
* on infinity.
*/
dict_set_bounds(stage1_dict);
dict_set_values(stage1_dict);
}

// Free the original dictionary.
dict_free(orig_dict);

iset = dict_get_infeasible_rows(stage1_dict);

// Return False if we didn't do any initialization.
if ((uvars.size + iset.size) == 0) {
return FALSE;
}

/*
* Set the appropriate dictionary reference and return True if we had to
* split some variables.
*/
if (iset.size == 0) {
*dict = stage1_dict;
return TRUE;
}

// Allocate a new dictionary with enough space for the auxilary variables.
stage2_dict = dict_new(stage1_dict->num_vars + iset.size, stage1_dict->num_cons);
stage2_dict->num_aux_vars = iset.size;
stage2_dict->num_split_vars = stage1_dict->num_split_vars;
stage2_dict->split_vars = stage1_dict->split_vars;

stage1_dict->split_vars = NULL;

// Copy the stage 1 dictionary values into the stage 2 dictionary.
dict_copy(stage2_dict, stage1_dict);

// Free the stage 1 dictionary.
dict_free(stage1_dict);

// Do the Electric Boogaloo
stage2_dict->objective2 = calloc(stage2_dict->num_vars, sizeof(double));

for (col_index = stage2_dict->num_vars; col_index-- > 0;) {
if (col_index < stage2_dict->num_vars - iset.size) {
stage2_dict->objective2[col_index] = stage2_dict->objective[col_index];

} else {
stage2_dict->objective2[col_index] = 0;
}
}

// Initialize the new objective function.
for (col_index = stage2_dict->num_vars; col_index-- > 0;) {
stage2_dict->objective[col_index] = 0.0;
}

// Add the new auxilary variables.
dict_add_aux_vars(stage2_dict, iset);

// Perform simplex.
dict_set_values(stage2_dict);
general_simplex_kernel(stage2_dict);

// Check original problem feasability.
if (-1e-5 > stage2_dict->objective_value || stage2_dict->objective_value > 1e-5) {
printf("Problem is infeasible: %f.\n", stage2_dict->objective_value);
exit(0);
}

// Replace objective function.
free(stage2_dict->objective);
stage2_dict->objective = stage2_dict->objective2;
stage2_dict->objective2 = NULL;

// Re-calculate the objective value.
dict_set_objective_value(stage2_dict);

// Remove auxilary variables.
stage2_dict = dict_remove_aux_vars(stage2_dict);

// Adjust bounds on any remaining auxilary variables.
if (stage2_dict->num_aux_vars > 0) {
last_orig_var_label = stage2_dict->num_vars + stage2_dict->num_cons - stage2_dict->num_aux_vars - stage2_dict->num_split_vars;

for (row_index = stage2_dict->num_cons; row_index-- > 0;) {
if (stage2_dict->row_labels[row_index] >= last_orig_var_label) {
stage2_dict->row_bounds.upper[row_index] = 0.0;
stage2_dict->row_bounds.lower[row_index] = 0.0;
}
}
}

// Set the appropriate dictionary reference and return True.
*dict = stage2_dict;
return TRUE;
}

bool dict_is_final(const dict_t* dict) {
uint col_index;

for (col_index = dict->num_vars; col_index-- > 0;) {
if ((dict->objective[col_index] < 0 && dict->col_rests[col_index] == UPPER) || (dict->objective[col_index] > 0 && dict->col_rests[col_index] == LOWER)) {
return FALSE;
}
}

return TRUE;
}

dict_t* dict_new(uint num_vars, uint num_cons) {
dict_t* dict;

/*
* Allocate the necessary memory.
*/

dict = malloc(sizeof(dict_t));

// Initialize the matrix.
matrix_init(&dict->matrix, num_cons, num_vars);

dict->objective = (double*)malloc(num_vars * sizeof(double));
dict->objective2 = NULL;
dict->row_values = (double*)malloc(num_cons * sizeof(double));

dict->col_labels = (int*)malloc(num_vars * sizeof(uint));
dict->row_labels = (int*)malloc(num_cons * sizeof(uint));

dict->row_bounds.upper = (double*)malloc(num_cons * sizeof(double));
dict->row_bounds.lower = (double*)malloc(num_cons * sizeof(double));

dict->col_bounds.upper = (double*)malloc(num_vars * sizeof(double));
dict->col_bounds.lower = (double*)malloc(num_vars * sizeof(double));

dict->col_rests = (rest_t*)malloc(num_vars * sizeof(rest_t));

dict->split_vars = NULL;

// Set the number of variables and constraints for the dictionary.
dict->num_vars = num_vars;
dict->num_cons = num_cons;
dict->num_aux_vars = 0;
dict->num_split_vars = 0;

return dict;
}

/*
* Pivots a dictionary around the given column and row.
*
* The col_index corresponds with the entering variable, and the row_index
* corresponds with the leaving variable.
*
* Starts with (1):
* xm = c1*x1 + c2*x2 + ... + cn*xn
*
* Converts to (2):
* -cj*xn = c1*x1 + c2*x2 + 1*xm + ... + cn*xn
*
* Then to (3):
* xn = (c1/-cj)*x1 + (c2/-cj)*x2 + (1/-cj)*xm + ... + (cn/-cj)*xn
*/
dict_t* dict_pivot(dict_t* dict, uint var_index, uint con_index, rest_t new_rest, double adj_amount) {
uint row_index, col_index;

double coefficient, swap;
double* tmp_row;

// Allocate space for our work.
tmp_row = (double*)malloc(dict->num_vars * sizeof(double));

// Copy the pivot row.
memcpy(tmp_row, matrix_get_row(&dict->matrix, con_index), dict->num_vars * sizeof(double));

/*
* Grab the coefficient from the pivot column and then replace it,
* converting to (2).
*/
coefficient = -tmp_row[var_index];
tmp_row[var_index] = -1.0;

// Divide the vector by the coefficient, converting to (3).
for (row_index = 0; row_index < dict->num_vars; ++row_index) {
tmp_row[row_index] /= coefficient;
}

// Replace old row with new row.
memcpy(matrix_get_row(&dict->matrix, con_index), tmp_row, dict->num_vars * sizeof(double));

/*
* Update the constraint values and then substitute new rows into old rows
* in the matrix.
*/

if (cfg.pmode == OMP) {
#pragma omp parallel for schedule(dynamic, 20) private(coefficient, row_index, col_index) shared(adj_amount)
for (row_index = 0; row_index < dict->num_cons; ++row_index) {
if (row_index == con_index) {
dict->row_values[row_index] = dict_get_var_bound_value(dict, var_index) + adj_amount;

} else {
coefficient = matrix_get_value(&dict->matrix, row_index, var_index);

dict->row_values[row_index] += coefficient * adj_amount;

for (col_index = dict->num_vars; col_index-- > 0;) {
if (col_index == var_index) {
matrix_set_value(&dict->matrix, row_index, col_index, coefficient * tmp_row[col_index]);

} else {
matrix_accum_value(&dict->matrix, row_index, col_index, coefficient * tmp_row[col_index]);
}

if (FPN_IS_ZERO(matrix_get_value(&dict->matrix, row_index, col_index))) matrix_set_value(&dict->matrix, row_index, col_index, 0.0);
}
}

if (FPN_IS_ZERO(dict->row_values[row_index])) dict->row_values[row_index] = 0.0;
}
} else {
for (row_index = dict->num_cons; row_index-- > 0;) {
if (row_index == con_index) {
dict->row_values[row_index] = dict_get_var_bound_value(dict, var_index) + adj_amount;

} else {
coefficient = matrix_get_value(&dict->matrix, row_index, var_index);

dict->row_values[row_index] += coefficient * adj_amount;

for (col_index = dict->num_vars; col_index-- > 0;) {
if (col_index == var_index) {
matrix_set_value(&dict->matrix, row_index, col_index, coefficient * tmp_row[col_index]);

} else {
matrix_accum_value(&dict->matrix, row_index, col_index, coefficient * tmp_row[col_index]);
}

if (FPN_IS_ZERO(matrix_get_value(&dict->matrix, row_index, col_index))) matrix_set_value(&dict->matrix, row_index, col_index, 0.0);
}
}

if (FPN_IS_ZERO(dict->row_values[row_index])) dict->row_values[row_index] = 0.0;
}
}

// Perform the same steps for the objective function.
coefficient = dict->objective[var_index];
dict->objective_value += coefficient * adj_amount;

if (FPN_IS_ZERO(dict->objective_value)) dict->objective_value = 0.0;

for (col_index = dict->num_vars; col_index-- > 0;) {
if (col_index == var_index) {
dict->objective[col_index] = coefficient * tmp_row[col_index];

} else {
dict->objective[col_index] += coefficient * tmp_row[col_index];
}

if (FPN_IS_ZERO(dict->objective[col_index])) dict->objective[col_index] = 0.0;
}

if (!cfg.init_done) {
coefficient = dict->objective2[var_index];
for (col_index = dict->num_vars; col_index-- > 0;) {
swap = dict->objective2[col_index];

if (col_index == var_index) {
dict->objective2[col_index] = coefficient * tmp_row[col_index];

} else {
dict->objective2[col_index] += coefficient * tmp_row[col_index];
}

if (FPN_IS_ZERO(dict->objective2[col_index])) dict->objective2[col_index] = 0.0;
}
}

/*
* Swap bounds and labels
*/

swap = dict->col_labels[var_index];
dict->col_labels[var_index] = dict->row_labels[con_index];
dict->row_labels[con_index] = swap;

swap = dict->col_bounds.upper[var_index];
dict->col_bounds.upper[var_index] = dict->row_bounds.upper[con_index];
dict->row_bounds.upper[con_index] = swap;

swap = dict->col_bounds.lower[var_index];
dict->col_bounds.lower[var_index] = dict->row_bounds.lower[con_index];
dict->row_bounds.lower[con_index] = swap;

// Set the new resting bound appropriately.
dict->col_rests[var_index] = new_rest;

// Free our temporary row.
free(tmp_row);

if (cfg.init_done) {
// Remove any auxilary variables that are now out of the basis.
return dict_remove_aux_vars(dict);

} else {
return dict;
}
}

dict_t* dict_remove_aux_vars(dict_t* orig_dict) {
uint col_index0, col_index1, row_index;
uint remove_count = 0;
int last_orig_var_label;

dict_t* new_dict;

// Nothing to remove. Return early.
if (orig_dict->num_aux_vars == 0) {
return orig_dict;
}

last_orig_var_label = orig_dict->num_vars + orig_dict->num_cons - orig_dict->num_aux_vars - orig_dict->num_split_vars;

// Count the number of auxilary variables we are going to remove.
for (col_index0 = orig_dict->num_vars; col_index0-- > 0;) {
if (orig_dict->col_labels[col_index0] > last_orig_var_label) {
++remove_count;
}
}

// Nothing to remove. Return early.
if (remove_count == 0) {
return orig_dict;
}

// Alocate our new dictionary.
new_dict = dict_new(orig_dict->num_vars - remove_count, orig_dict->num_cons);

/*
* Selectivly copy/move data to new dictionary.
*/
new_dict->num_aux_vars = orig_dict->num_aux_vars - remove_count;
new_dict->num_split_vars = orig_dict->num_split_vars;

new_dict->split_vars = orig_dict->split_vars;
orig_dict->split_vars = NULL;

new_dict->objective_value = orig_dict->objective_value;

// Copy the matrix.
for (row_index = orig_dict->num_cons; row_index-- > 0;) {
for (col_index0 = col_index1 = 0; col_index0 < orig_dict->num_vars; ++col_index0) {
if (orig_dict->col_labels[col_index0] <= last_orig_var_label) {
matrix_set_value(&new_dict->matrix, row_index, col_index1, matrix_get_value(&orig_dict->matrix, row_index, col_index0));

++col_index1;
}
}
}

// Copy row data.
for (row_index = new_dict->num_cons; row_index-- > 0;) {
// Labels
new_dict->row_labels[row_index] = orig_dict->row_labels[row_index];

// Bounds
new_dict->row_bounds.upper[row_index] = orig_dict->row_bounds.upper[row_index];
new_dict->row_bounds.lower[row_index] = orig_dict->row_bounds.lower[row_index];

// Values
new_dict->row_values[row_index] = orig_dict->row_values[row_index];
}

// Copy column data.
for (col_index0 = col_index1 = 0; col_index0 < orig_dict->num_vars; ++col_index0) {
if (orig_dict->col_labels[col_index0] <= last_orig_var_label) {
// Labels
new_dict->col_labels[col_index1] = orig_dict->col_labels[col_index0];

// Bounds
new_dict->col_bounds.upper[col_index1] = orig_dict->col_bounds.upper[col_index0];
new_dict->col_bounds.lower[col_index1] = orig_dict->col_bounds.lower[col_index0];

// Rests
new_dict->col_rests[col_index1] = orig_dict->col_rests[col_index0];

// Objective
new_dict->objective[col_index1] = orig_dict->objective[col_index0];

++col_index1;
}
}

dict_free(orig_dict);
return new_dict;
}

inline bool dict_row_is_feasible(const dict_t* dict, uint con_index) {
double con_value = dict->row_values[con_index];

return dict->row_bounds.lower[con_index] <= con_value && con_value <= dict->row_bounds.upper[con_index];
}

void dict_select_entering_and_leaving(const dict_t* dict, elr_t* result) {
uint col_index, row_index, min_sub = INT_MAX;
double max_constraint;

clr_t cl_result;

if (cfg.vv) {
printf("Entering and leaving variable analysis:\n");
}

// Select the entering variable.
for (col_index = dict->num_vars; col_index-- > 0;) {
if (dict_var_can_enter(dict, col_index)) {

if (cfg.vv) {
printf("\tx%u can enter.\n", dict->col_labels[col_index]);
}

if (cfg.blands) {
if (dict->col_labels[col_index] < min_sub) {
if (cfg.vv) printf("\tSelecting x%u as entering variable due to Bland's Rule\n", dict->col_labels[col_index]);

result->entering = col_index;
min_sub = dict->col_labels[col_index];
}

} else {

if (cfg.vv) printf("\tSelecting x%u as entering variable.\n", dict->col_labels[col_index]);

result->entering = col_index;
break;
}
}
}

if (cfg.vv) printf("\n");

/*
* Pick the leaving variable.
*/
if (dict->objective[result->entering] < 0 && dict->col_rests[result->entering] == UPPER && dict->col_bounds.lower[result->entering] != -INFINITY) {
max_constraint = fabs(dict->col_bounds.upper[result->entering] - dict->col_bounds.lower[result->entering]);

if (cfg.vv) printf("\tx%u can flip to its LOWER bound: t ≤ %- 7.3g\n\n", dict->col_labels[result->entering], max_constraint);

result->flip = TRUE;
result->new_rest = LOWER;

} else if (dict->objective[result->entering] > 0 && dict->col_rests[result->entering] == LOWER && dict->col_bounds.upper[result->entering] != INFINITY) {
max_constraint = fabs(dict->col_bounds.upper[result->entering] - dict->col_bounds.lower[result->entering]);

if (cfg.vv) printf("\tx%u can flip to its UPPER bound: t ≤ %- 7.3g\n\n", dict->col_labels[result->entering], max_constraint);

result->flip = TRUE;
result->new_rest = UPPER;

} else {
max_constraint = INFINITY;
result->flip = FALSE;
}

for (row_index = dict->num_cons; row_index-- > 0;) {
dict_var_can_leave(dict, &cl_result, result->entering, row_index);

if (cl_result.viable) {

if (cfg.vv) printf("\tx%u can leave: t ≤ %- 7.3g\n", dict->row_labels[row_index], cl_result.constraint);

// Found a new, more constraining, choice.
if (cl_result.constraint < max_constraint ||
(cfg.blands && (cl_result.constraint == max_constraint && dict->row_labels[row_index] < min_sub))) {

if (cfg.vv) printf("\tSelecting x%u as leaving variable.\n", dict->row_labels[row_index]);

max_constraint = cl_result.constraint;
min_sub = dict->row_labels[row_index];

result->leaving = row_index;
result->new_rest = cl_result.new_rest;
result->flip = FALSE;
}
}
}

// Set the adjustment amount to be used during pivoting.
result->adj_amount = dict->col_rests[result->entering] == UPPER ? -max_constraint : max_constraint;

if (cfg.vv) {
if (result->flip) {
printf("\n\tFlip x%u\n\n", dict->col_labels[result->entering]);
} else {
printf("\n\tPivot with x%u entering and x%u leaving.\n\n", dict->col_labels[result->entering], dict->row_labels[result->leaving]);
}
}
}

void dict_set_bounds(dict_t* dict) {
uint col_index;

// Pick the initial resting bounds for the variables.
for (col_index = dict->num_vars; col_index-- > 0;) {
if ((dict->objective[col_index] >= 0 && dict->col_bounds.upper[col_index] != INFINITY) || (dict->col_bounds.lower[col_index] == -INFINITY)) {
dict->col_rests[col_index] = UPPER;

} else {
dict->col_rests[col_index] = LOWER;
}
}
}

inline void dict_set_objective_value(dict_t* dict) {
uint col_index;

dict->objective_value = 0.0;
for (col_index = dict->num_vars; col_index-- > 0;) {
dict->objective_value += dict->objective[col_index] * dict_get_var_bound_value(dict, col_index);
}
}

void dict_set_values(dict_t* dict) {
uint row_index;

// Calculate the values of the constraints.
for (row_index = dict->num_cons; row_index-- > 0;) {
dict->row_values[row_index] = dict_get_constraint_value(dict, row_index);
}

// Calculate the value of the objective.
dict_set_objective_value(dict);
}

bool dict_var_can_enter(const dict_t* dict, uint var_index) {
if ( (dict->objective[var_index] < 0 && dict->col_rests[var_index] == UPPER) ||
(dict->objective[var_index] > 0 && dict->col_rests[var_index] == LOWER)) {

return TRUE;

} else {
return FALSE;
}
}

/*
* Determines if a variable (referenced by the corresponding row in the matrix)
* can leave when a given variable (referenced by the corresponding column in
* the matrix) is entering.
*/
void dict_var_can_leave(const dict_t* dict, clr_t* result, uint var_index, uint con_index) {
double con_value;
double t_coef;
double* row = matrix_get_row(&dict->matrix, con_index);

// If the entering variable's coefficient is 0 this variable can't leave.
if (FPN_IS_ZERO(row[var_index])) {
result->viable = FALSE;
return;
}

/*
* Accumulate the constant given the resting bounds for the non-basic
* variables.
*/
con_value = dict->row_values[con_index];

// Get the coefficient for t.
t_coef = dict->col_rests[var_index] == UPPER ? -1.0 : 1.0;
t_coef *= row[var_index];

/*
* Calculate the amount this leaving variable choice constrains the
* entering variable's value.
*/
if (dict->row_bounds.lower[con_index] <= con_value && t_coef < 0) {
result->viable = TRUE;
result->constraint = (dict->row_bounds.lower[con_index] - con_value) / t_coef;
result->new_rest = LOWER;

} else if (con_value <= dict->row_bounds.upper[con_index] && t_coef > 0) {
result->viable = TRUE;
result->constraint = (dict->row_bounds.upper[con_index] - con_value) / t_coef;
result->new_rest = UPPER;

} else {
result->viable = FALSE;
}
}

inline bool dict_var_is_unbounded(const dict_t* dict, uint var_index) {
return -INFINITY == dict->col_bounds.lower[var_index] && dict->col_bounds.upper[var_index] == INFINITY;
}

bool dict_var_was_split(const dict_t* dict, int var_label) {
uint index;

if (var_label < 0) return FALSE;

for (index = dict->num_split_vars; index-- > 0;) {
if (dict->split_vars[index] == var_label) {
return TRUE;
}
}

return FALSE;
}

void dict_view(const dict_t* dict) {
uint col_index, row_index;
double tmp;
char buffer[10];

// Print column labels.
printf(" ");
for (col_index = 0; col_index < dict->num_vars; ++col_index) {
if (dict->col_labels[col_index] >= 0) {
snprintf(buffer, 10, "x%u", dict->col_labels[col_index]);

} else {
snprintf(buffer, 10, "-x%u", -dict->col_labels[col_index]);
}

printf("%8s", buffer);
}
printf(" value\n");

// Print bounds, labels, and values for rows.
for (row_index = 0; row_index < dict->num_cons; ++row_index) {
// Format the column label.
if (dict->row_labels[row_index] >= 0) {
snprintf(buffer, 10, "x%u", dict->row_labels[row_index]);

} else {
snprintf(buffer, 10, "-x%u", -dict->row_labels[row_index]);
}

// Print out bounds and label info.
printf("% 7.3g % 7.3g | %5s |", dict->row_bounds.lower[row_index], dict->row_bounds.upper[row_index], buffer);

for (col_index = 0; col_index < dict->num_vars; ++col_index) {
tmp = matrix_get_value(&dict->matrix, row_index, col_index);
printf(" % 7.2g", tmp == -0 ? 0 : tmp);
}

// Print the constraint's value.
printf(" | % 7.3g", dict->row_values[row_index]);

printf("\n");
}

// Print seperator.
printf("-----------------------------------");
for (col_index = 0; col_index < dict->num_vars; ++col_index) {
printf("--------");
}
printf("\n");

// Print objective function coefficients.
printf(" z |");
for (col_index = 0; col_index < dict->num_vars; ++col_index) {
printf(" % 7.3g", dict->objective[col_index]);
}
printf("\n");

// Print the variables' lower bounds.
printf(" | ");
for (col_index = 0; col_index < dict->num_vars; ++col_index) {
printf(dict->col_rests[col_index] == LOWER ? " [% 5.2g]" : " % 5.2g ", dict->col_bounds.lower[col_index]);
}
printf("\n");

// Print the variables' upper bounds.
printf(" | ");
for (col_index = 0; col_index < dict->num_vars; ++col_index) {
printf(dict->col_rests[col_index] == UPPER ? " [% 5.2g]" : " % 5.2g ", dict->col_bounds.upper[col_index]);
}
printf("\n\n");
}

void dict_view_answer(const dict_t* dict) {
uint var_index;
uint num_orig_vars;
char buffer[10];

num_orig_vars = dict->num_vars - dict->num_aux_vars - dict->num_split_vars;

printf("\t z = %g\n", dict->objective_value);

for (var_index = 1; var_index <= num_orig_vars; ++var_index) {
snprintf(buffer, 10, "x%u", var_index);
printf("\t%4s = %g\n", buffer, dict_get_var_value_by_label(dict, var_index));
}
}
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