Fix to avoid overwriting a container's content when used as a function's default value

theano/compile/function_module.py

@@ -235,7 +235,12 @@ class Function(object):
                 if input.strict:
                     c.strict = True
                 if value is not None:
-                    # always initialize the storage
+                    # Always initialize the storage.
+                    if isinstance(value, gof.Container):
+                        # We obtain the default value from whatever value is currently
+                        # stored in the default container.
+                        assert len(value.storage) == 1
+                        value = value.storage[0]
                     c.data = value
                 c.required = required
                 c.provided = 0 # this is a count of how many times the input has been provided (reinitialized to 0 on __call__)
@@ -382,6 +387,8 @@ class Function(object):
         # Put default values back in the storage
         for i, (required, refeed, value) in enumerate(self.defaults):
             if refeed:
+                if isinstance(value, gof.Container):
+                    value = value.storage[0]
                 self[i] = value
         if self.return_none:
             return None
@@ -643,32 +650,39 @@ class FunctionMaker(object):
 
         # The following loop is to fill in the input_storage and _defaults lists.
         for (input, indices, subinputs), default in zip(self.indices, defaults):
+            # Replace any default value given as a variable by its container.
+            # Note that this makes sense only in the context of shared variables,
+            # but for now we avoid dealing directly with them to avoid dependency
+            # on the shared variables work-in-progress repository.
+            if isinstance(default, gof.Variable):
+                default = default.container
+
             __default = default
 
-            if isinstance(default, gof.Container):
-                # If the default is a gof.Container, this means we want to share
-                # the same storage. This is done by appending default.storage
-                # to input_storage
-                if indices is not None:
-                    raise TypeError("Cannot take a Container instance as default for a SymbolicInputKit.")
-                input_storage.append(default.storage)
-                default = None
-                required = False
-            elif isinstance(input, SymbolicInputKit):
+            #if isinstance(default, gof.Container):
+                ## If the default is a gof.Container, this means we want to share
+                ## the same storage. This is done by appending default.storage
+                ## to input_storage
+                #if indices is not None:
+                    #raise TypeError("Cannot take a Container instance as default for a SymbolicInputKit.")
+                #input_storage.append(default.storage)
+                #default = None
+                #required = False
+            if isinstance(input, SymbolicInputKit):
                 # If the input is a SymbolicInputKit, it represents more than
                 # one storage unit. The indices and subinputs lists represent which
                 # of the kit's inputs are active in this graph, so we make as many
                 # storage units as needed
-                if isinstance(default, (list, tuple)) \
-                        and all(isinstance(x, gof.Container) for x in default):
-                    if len(default) == len(indices):
-                        input_storage += [x.storage for x in default]
-                    elif len(default) > len(indices):
-                        input_storage += [default[i].storage for i in indices]
-                    else:
-                        raise ValueError('Not enough storage for SymbolicInputKit', input, indices, default)
-                    default = NODEFAULT
-                else:
+                #if isinstance(default, (list, tuple)) \
+                        #and all(isinstance(x, gof.Container) for x in default):
+                    #if len(default) == len(indices):
+                        #input_storage += [x.storage for x in default]
+                    #elif len(default) > len(indices):
+                        #input_storage += [default[i].storage for i in indices]
+                    #else:
+                        #raise ValueError('Not enough storage for SymbolicInputKit', input, indices, default)
+                    #default = NODEFAULT
+                #else:
                     input_storage += [[None] for i in indices]
             else:
                 # Normal case: one new, independent storage unit
@@ -695,7 +709,7 @@ class FunctionMaker(object):
                 # back into the storage as it would defeat the point of updating it. We
                 # always do this policy.
                 if default is None:
-                    if trustme or isinstance(__default, gof.Container):
+                    if trustme: #or isinstance(__default, gof.Container):
                         _defaults.append((False, False, None))
                     else:
                         # This might catch some bugs early
@@ -704,7 +718,7 @@ class FunctionMaker(object):
                     _defaults.append((False, False, default))
             else:
                 if default is None:
-                    if trustme or isinstance(__default, gof.Container):
+                    if trustme: #or isinstance(__default, gof.Container):
                         _defaults.append((False, False, None))
                     else:
                         # No default, so this is a required input. Nothing to feed back, initial value is None.
@@ -820,6 +834,7 @@ def function(inputs, outputs, mode=None, accept_inplace = False):
         else:              
             #return a different kind of function
             def dup_defaults():
+                # TODO This may need to be changed to use containers as defaults.
                 return [copy.copy(default.value) if isinstance(default, gof.Container) else
                         copy.copy(default)
                         for default in defaults]