fixes bug in mul canonizer

theano/tensor/opt.py

@@ -638,6 +638,7 @@ class Canonizer(gof.LocalOptimizer):
 
         # Lists representing the numerator and denumerator
         num, denum = list(orig_num), list(orig_denum)
+        out_type = self.merge_num_denum(orig_num, orig_denum).type
 
         # Lists representing the *constant* elements of num and denum
         numct, denumct = [], []
@@ -660,14 +661,14 @@ class Canonizer(gof.LocalOptimizer):
             # This will calculate either:
             # [inverse(main(*numct), main(*denumct))]
             # [] - if inverse(main(*numct), main(*denumct)) is the neutral element
-            ct = self.calculate(numct, denumct, aslist = True)
+            ct = self.calculate(numct, denumct, aslist = True, out_type=out_type)
         else:
             # This happens if we don't allow the reciprocal and the
             # numerator is empty. That means we will need to represent
             # reciprocal(x) like inverse(neutral_element, x) so
             # we can't allow ct == []
             # TODO: why is this branch needed when merge_num_denum does it for us?
-            ct = [self.calculate(numct, denumct, aslist = False)]
+            ct = [self.calculate(numct, denumct, aslist = False, out_type=out_type)]
         # TODO: why are we not wrapping ct in a gof.Constant right now?
 
         if orig_num and len(numct) == 1 and len(denumct) == 0 and ct and N.all(ct == self.get_constant(orig_num[0])):
@@ -725,13 +726,17 @@ class Canonizer(gof.LocalOptimizer):
         return getattr(self, 'name', 'Canonizer(%s, %s, %s)' % (self.main, self.inverse, self.reciprocal))
 
 
-def mul_calculate(num, denum, aslist=False):
+def mul_calculate(num, denum, aslist=False, out_type=None):
     if not num and not denum:
         # Smallest 1 possible.
         return [] if aslist else N.int8(1)
     # Make sure we do not accidently upcast data types.
-    first = num[0] if num else denum[0]
-    one = N.asarray(first).dtype.type(1)
+    if out_type is None:
+        # TODO: remove this error-causing heuristic
+        first = num[0] if num else denum[0]
+        one = N.asarray(first).dtype.type(1)
+    else:
+        one = N.asarray(1, dtype=out_type.dtype)
     v = reduce(N.multiply, num, one) / reduce(N.multiply, denum, one)
     if aslist:
         if N.all(v == 1):
@@ -898,8 +903,10 @@ mul_canonizer = in2out(gof.LocalOptGroup(local_mul_canonizer, local_fill_cut, lo
 
 
 
-def add_calculate(num, denum, aslist = False):
-    v = reduce(N.add, num, 0.0) - reduce(N.add, denum, 0.0)
+def add_calculate(num, denum, aslist = False, out_type=None):
+    #TODO: make sure that this function and mul_calculate are similar
+    zero = 0.0 if out_type is None else N.asarray(0, dtype=out_type.dtype)
+    v = reduce(N.add, num, zero) - reduce(N.add, denum, zero)
     if aslist:
         if N.all(v == 0):
             return []