Changeset 2314

Timestamp:

Feb 1, 2006, 3:27:53 PM (19 years ago)

Author:

sexton

Message:

Investigating 0/0 and 1/0 in apply_expression_to_dictionary

Location:

inundation/pyvolution

Files:

• test_util.py (modified) (4 diffs)
• util.py (modified) (2 diffs)

inundation/pyvolution/test_util.py

@@ -3 +3 @@
 
 import unittest
-from Numeric import zeros, array, allclose
+from Numeric import zeros, array, allclose, Float
 from math import sqrt, pi
 
@@ -974 +974 @@
     def test_apply_expression_to_dictionary(self):
 
+        #FIXME: Division is not expected to work for integers.
+        #This must be caught.
         foo = array([[1,2,3],
-                     [4,5,6]])
+                     [4,5,6]], Float)
 
         bar = array([[-1,0,5],
-                     [6,1,1]])                  
+                     [6,1,1]], Float)                  
 
         D = {'X': foo, 'Y': bar}
@@ -990 +992 @@
         Z = apply_expression_to_dictionary('4*X+Y', D)        
         assert allclose(Z, 4*foo+bar)        
+
+        # test zero division is OK
+        Z = apply_expression_to_dictionary('X/Y', D)
+        assert allclose(1/Z, 1/(foo/bar)) # can't compare inf to inf
+
+        # make an error for zero on zero
+        # this is really an error in Numeric, SciPy core can handle it
+        # Z = apply_expression_to_dictionary('0/Y', D)
 
         #Check exceptions
@@ -1046 +1056 @@
 if __name__ == "__main__":
     suite = unittest.makeSuite(Test_Util,'test')
-    #suite = unittest.makeSuite(Test_Util,'test_file_function_time')
+    #suite = unittest.makeSuite(Test_Util,'test_apply')
     runner = unittest.TextTestRunner()
     runner.run(suite)

inundation/pyvolution/util.py

@@ -509 +509 @@
                 will be evaluated by expression.
                 Values in dictionary must support operators given in
-                expression e.g. by overloading                
+                expression e.g. by overloading
+
+    due to a limitation with Numeric, this can not evaluate 0/0
+    In general, the user can fix by adding 1e-30 to the numerator.
+    SciPy core can handle this situation.
     """
 
@@ -532 +536 @@
         msg = 'Expression "%s" could not be evaluated: %s' %(expression, e)
         raise NameError, msg
+    except ValueError, e:
+        msg = 'Expression "%s" could not be evaluated: %s' %(expression, e)
+        raise ValueError, msg