Fix for some shape-related errors on 32-bit

theano/tensor/opt.py

@@ -920,6 +920,28 @@ class ShapeFeature(object):
                     + ' != len(node.outputs) = '
                     + str(len(node.outputs)))
 
+        # Ensure shapes are in 'int64'. This is to make sure the assert
+        # found in the `local_useless_subtensor` optimization does not fail.
+        new_shape = []
+        for sh_idx, sh in enumerate(o_shapes):
+            if sh is None:
+                continue
+            for i, d in enumerate(sh):
+                # Note: we ignore any shape element that is not typed (i.e. does
+                # not have a 'dtype' attribute). This means there may still
+                # remain int elements that are int32 on 32-bit platforms, but
+                # this works with `local_useless_subtensor`, so for now we
+                # keep it this way. See #266 for a better long-term fix.
+                if getattr(d, 'dtype', 'int64') != 'int64':
+                    assert d.dtype in theano.tensor.int_dtypes
+                    new_shape += sh[len(new_shape):i + 1]
+                    new_shape[i] = theano.tensor.cast(d, 'int64')
+            if new_shape:
+                # We replace the shape with wrong dtype by the one with 'int64'.
+                new_shape += sh[len(new_shape):]
+                o_shapes[sh_idx] = tuple(new_shape)
+                new_shape = []
+
         for r, s in izip(node.outputs, o_shapes):
             self.set_shape(r, s)