add a isnull function to really determine if a smrt_matrix is null

smrt/core/fresnel.py

@@ -4,7 +4,6 @@
 """
 
 import numpy as np
-import scipy.sparse
 from smrt.core.lib import smrt_matrix, abs2
 
 

smrt/core/lib.py

@@ -120,7 +120,7 @@ class smrt_matrix(object):
     def __init__(self, mat, mtype=None):
 
         if mat is 0:
-            self.values = 0
+            self.values = 0.
             self.mtype = "0"
         else:
             self.values = mat
@@ -176,7 +176,7 @@ def compress(self, mode=None, auto_reduce_npol=False):
         3) convert the format of the matrix to compressed numpy, involving a change of the dimension order (pola and streams are merged).
 
 """
-        if self.values is 0:
+        if self.mtype == "0":
             return 0.
 
         if self.mtype == "dense5":
@@ -264,7 +264,7 @@ def __setitem__(self, key, v):
 
     @property
     def diagonal(self):
-        if self.values is 0:
+        if self.mtype == "0":
             return np.array([0.])
         if self.mtype.startswith("diagonal"):
             return self.values
@@ -306,6 +306,16 @@ def __repr__(self):
         return str("smrt_matrix %s %s" % (self.mtype, shape)) + "\n" + str(self.values)
 
 
+def isnull(m):
+    """return true if the smrt matrix is null"""
+
+    if isinstance(m, scipy.sparse.dia.dia_matrix):
+        m = m.diagonal()
+
+    return (m is 0) or \
+            (getattr(m, "mtype", None) == "0") or \
+             (~np.any(m))
+
 
 def abs2(c):
     return c.real**2 + c.imag**2