Make LocalOptGroup able to register tracks of None and simplify the opt related to ViewOp.

theano/gof/opt.py

@@ -1333,8 +1333,11 @@ class LocalOptGroup(LocalOptimizer):
                 self.process_count.setdefault(o, 0)
                 self.applied_true.setdefault(o, 0)
                 self.node_created.setdefault(o, 0)
-
-            for c in o.tracks():
+            tracks = o.tracks()
+            if tracks is None:
+                self.track_map[None].append(o)
+            else:
+                for c in tracks:
                     self.track_map[c].append(o)
 
     def __str__(self):

theano/tensor/opt.py

@@ -7487,23 +7487,15 @@ def local_useless_composite(node):
 # # Remove consider_constant #
 # ############################
 
+
 # Although the ops ConsiderConstant, ZeroGrad and DisconnectedGrad
 # just returns the input, it should be removed from the graph to
-# make sure all possible optimizations can be applied.
-for o, name in [(gof.OpRemove(theano.gradient.consider_constant_),
-                 "remove_consider_constant"),
-                (gof.OpRemove(theano.gradient.zero_grad_),
-                 'remove_zero_grad'),
-                (gof.OpRemove(theano.gradient.disconnected_grad_),
-                 'remove_disconnected_grad'),
-                (gof.OpRemove(theano.gradient.undefined_grad_),
-                 'remove_undefined_grad'),
-                (gof.OpRemove(theano.gradient.GradClip),
-                 'remove_grad_clip'),
-                (gof.OpRemove(theano.gradient.GradScale),
-                 'remove_grad_scale')]:
-    register_canonicalize(o, 'fast_compile', 'fast_run', name=name)
-    register_useless(o, 'fast_compile', 'fast_run', name=name)
+@register_canonicalize('fast_compile')
+@register_useless('fast_compile')
+@gof.local_optimizer(None)
+def local_view_op(node):
+    if isinstance(node.op, theano.compile.ops.ViewOp):
+        return node.inputs
 
 
 @register_useless