call the Alloc instance don't return useless Alloc. This will be discussed in an…

theano/tensor/basic.py

@@ -1848,6 +1848,17 @@ class Alloc(gof.Op):
     def grad(self, inputs, (gout,)):
         return [None for i in inputs]
 
+    def __call__(self, *inputs, **kwargs):
+        """
+        Don't generate alloc that do nothing.
+        If you always want an Alloc node, call make_node.
+        """
+        ret = super(Alloc,self).__call__(*inputs,**kwargs)
+        import pdb;pdb.set_trace()
+        if inputs[0].type == ret.type:
+            return inputs[0]
+        else: return ret
+        
 alloc = Alloc()
 pprint.assign(alloc, printing.FunctionPrinter('alloc'))
 

theano/tensor/opt.py

@@ -757,8 +757,9 @@ def local_alloc_elemwise(node):
     new = []
     
     for i in node.inputs:
-        if i.owner and isinstance(i.owner.op,T.Alloc):
-            #I suppose that alloc input must have the same shape as the output.
+        if i.owner and isinstance(i.owner.op,T.Alloc) and i.owner.inputs[0].type != i.owner.outputs[0].type:
+            #when i.owner.inputs[0].type == i.owner.outputs[0].type we will remove that alloc later
+
             assert i.type.ndim == node.inputs[no_broad_idx].type.ndim
             new_i = i.owner.inputs[0]
             if theano.config.experimental.local_alloc_elemwise_assert: