Fix reshape.infer_shape

theano/tensor/basic.py

@@ -3795,11 +3795,29 @@ class Reshape(Op):
         # It's not trivial, because we would have to check if the product of
         # all the non-minus-one shapes is a divisor of the product of the
         # original shapes.
-        return [tuple([switch(eq(node.inputs[1][i], -1),
-                                 theano.tensor.opt.Shape_i(i)(node.outputs[0]),
-                                 node.inputs[1][i])
-                            for i in range(self.ndim)]
-            )]
+
+        # The following expression leads to cycles in feature_shape,
+        # because it tries to replace the Shape_i node by the switch
+        # statement, which depends on Shape_i.
+        #return [tuple([switch(eq(node.inputs[1][i], -1),
+        #                         theano.tensor.opt.Shape_i(i)(node.outputs[0]),
+        #                         node.inputs[1][i])
+        #                    for i in range(self.ndim)]
+        #    )]
+
+        # Here, we only simplify if the shape (node.inputs[1]) is a constant,
+        # ideally it would suffice to check that it is always non-negative.
+        oshape = []
+        for i in range(self.ndim):
+            default_os_i = theano.tensor.opt.Shape_i(i)(node.outputs[0])
+            try:
+                os_i = get_constant_value(node.inputs[1][i]).item()
+                if os_i == -1:
+                    os_i = default_os_i
+            except TypeError:
+                os_i = default_os_i
+            oshape.append(os_i)
+        return [tuple(oshape)]
 
 def reshape(x, newshape, ndim=None, name=None):
     if ndim is None: