Add the Theano flag optimizer_verbose

doc/library/config.txt

@@ -482,6 +482,14 @@ import theano and print the config variable, as in:
 
     This flag's value cannot be modified during the program execution.
 
+.. attribute:: optimizer_verbose
+
+    Bool value: either True or False
+
+    Default: False
+
+    When True, we print on the stdout the optimization applied.
+
 .. attribute:: nocleanup
 
     Bool value: either True or False

theano/configdefaults.py

@@ -157,6 +157,11 @@ AddConfigVar('optimizer',
         EnumStr('fast_run', 'merge', 'fast_compile', 'None'),
         in_c_key=False)
 
+AddConfigVar('optimizer_verbose',
+             "If True, we print all optimization being applied",
+             BoolParam(False),
+             in_c_key=False)
+
 AddConfigVar('on_opt_error',
         ("What to do when an optimization crashes: warn and skip it, raise "
          "the exception, or fall into the pdb debugger."),

theano/gof/fg.py

@@ -413,12 +413,15 @@ class FunctionGraph(utils.object2):
             self.__prune_r__([r], reason=reason)
 
     ### replace ###
-
-    def replace(self, r, new_r, reason=None):
+    def replace(self, r, new_r, reason=None, verbose=None):
         """ WRITEME
         This is the main interface to manipulate the subgraph in FunctionGraph.
         For every node that uses r as input, makes it use new_r instead.
         """
+        if verbose is None:
+            verbose = config.optimizer_verbose
+        if verbose:
+            print reason, r, new_r
         if r.fgraph is not self:
             raise Exception("Cannot replace %s because it does not belong to this FunctionGraph" % r, str(reason))
         if not r.type == new_r.type:

theano/gof/toolbox.py

 import sys
 import time
 
+from theano import config
 from theano.gof.python25 import partial
 from theano.gof.python25 import OrderedDict
 from theano.gof import graph
@@ -197,11 +198,14 @@ class ReplaceValidate(History, Validator):
     def replace_validate(self, fgraph, r, new_r, reason=None):
         self.replace_all_validate(fgraph, [(r, new_r)], reason=reason)
 
-    def replace_all_validate(self, fgraph, replacements, reason=None):
+    def replace_all_validate(self, fgraph, replacements,
+                             reason=None, verbose=None):
         chk = fgraph.checkpoint()
+        if verbose is None:
+            verbose = config.optimizer_verbose
         for r, new_r in replacements:
             try:
-                fgraph.replace(r, new_r, reason=reason)
+                fgraph.replace(r, new_r, reason=reason, verbose=False)
             except Exception, e:
                 if ('The type of the replacement must be the same' not in
                     str(e) and 'does not belong to this FunctionGraph' not in str(e)):
@@ -217,6 +221,8 @@ class ReplaceValidate(History, Validator):
         except Exception, e:
             fgraph.revert(chk)
             raise
+        if verbose:
+            print reason, r, new_r
         return chk
 
     def replace_all_validate_remove(self, fgraph, replacements,