Faster opt by not doing useless stuff.

theano/tensor/opt.py

@@ -2867,12 +2867,13 @@ class Canonizer(gof.LocalOptimizer):
         else:
             return v
 
-    def simplify(self, num, denum):
+    def simplify(self, num, denum, out_type):
         """
         Shorthand for:
         self.simplify_constants(*self.simplify_factors(num, denum))
         """
-        rval = self.simplify_constants(*self.simplify_factors(num, denum))
+        rval = self.simplify_constants(*self.simplify_factors(num, denum),
+                                       out_type=out_type)
         for reason, simplifier in self.external_simplifiers:
             # TODO: document that 'reason' is associated with this
             #       simplification to help auditing when things go
@@ -2896,7 +2897,7 @@ class Canonizer(gof.LocalOptimizer):
                 denum.remove(v)
         return num, denum
 
-    def simplify_constants(self, orig_num, orig_denum):
+    def simplify_constants(self, orig_num, orig_denum, out_type=None):
         """
 
         Finds all constants in orig_num and orig_denum (using
@@ -2914,7 +2915,6 @@ 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 = [], []
@@ -3001,7 +3001,7 @@ class Canonizer(gof.LocalOptimizer):
         # Here we make the canonical version of the graph around this node
         # See the documentation of get_num_denum and simplify
         orig_num, orig_denum = self.get_num_denum(node.outputs[0])
-        num, denum = self.simplify(list(orig_num), list(orig_denum))
+        num, denum = self.simplify(list(orig_num), list(orig_denum), out.type)
 
         def same(x, y):
             return len(x) == len(y) and all(N.all(xe == ye) for xe, ye in
@@ -3873,7 +3873,8 @@ register_canonicalize(local_add_canonizer, name='local_add_canonizer')
 ##################
 
 
-def distribute_greedy(pos_pairs, neg_pairs, num, denum, minscore=0):
+def distribute_greedy(pos_pairs, neg_pairs, num, denum,
+                      out_type, minscore=0):
     # each pair in pos_pairs and neg_pairs is a num/denum pair. this
     # function attempts to add num and denum to the corresponding parts
     # of each pair, and counts how many multiplications/divisions can
@@ -3889,10 +3890,10 @@ def distribute_greedy(pos_pairs, neg_pairs, num, denum, minscore=0):
     # score is number of operations saved, higher is better
     score = len(num) + div_cost * len(denum)
     new_pos_pairs = list(itertools.starmap(local_mul_canonizer.simplify,
-                                           [(n + num, d + denum) for (n, d)
+                                           [(n + num, d + denum, out_type) for (n, d)
                                             in pos_pairs]))
     new_neg_pairs = list(itertools.starmap(local_mul_canonizer.simplify,
-                                           [(n + num, d + denum) for (n, d)
+                                           [(n + num, d + denum, out_type) for (n, d)
                                             in neg_pairs]))
     for (n, d), (nn, dd) in zip(pos_pairs + neg_pairs, new_pos_pairs +
                                 new_neg_pairs):
@@ -3905,7 +3906,7 @@ def distribute_greedy(pos_pairs, neg_pairs, num, denum, minscore=0):
     return True, new_pos_pairs, new_neg_pairs
 
 
-def attempt_distribution(factor, num, denum):
+def attempt_distribution(factor, num, denum, out_type):
     # we try to insert each num and each denum in the factor
     # returns: changes?, new_factor, new_num, new_denum
     # if there are changes, new_num and new_denum contain all the numerators
@@ -3918,13 +3919,13 @@ def attempt_distribution(factor, num, denum):
     change = False
     for n in list(num):
         success, pos_pairs, neg_pairs = distribute_greedy(pos_pairs,
-                                                          neg_pairs, [n], [])
+                                                          neg_pairs, [n], [], out_type)
         if success:
             change = True
             num.remove(n)
     for d in list(denum):
         success, pos_pairs, neg_pairs = distribute_greedy(pos_pairs,
-                                                          neg_pairs, [], [d])
+                                                          neg_pairs, [], [d], out_type)
         if success:
             change = True
             denum.remove(d)
@@ -3969,12 +3970,13 @@ def local_greedy_distributor(node):
 
     change = False
 
+    out_type = out.type
     for candidate in list(num):
         if candidate not in num:
             continue
         num.remove(candidate)
         _change, candidate, num, denum = attempt_distribution(candidate,
-                                                              num, denum)
+                                                              num, denum, out_type)
         change |= _change
         new_num.append(candidate)
 
@@ -3983,7 +3985,7 @@ def local_greedy_distributor(node):
             continue
         denum.remove(candidate)
         _change, candidate, denum, num = attempt_distribution(candidate,
-                                                              denum, num)
+                                                              denum, num, out_type)
         change |= _change
         new_denum.append(candidate)