checking for empty tensors

theano/tensor/basic.py

@@ -4004,10 +4004,13 @@ class Join(Op):
     def perform(self, node, axis_and_tensors, out_):
         out, = out_
         axis, tensors = axis_and_tensors[0], axis_and_tensors[1:]
-        nonempty_tensors = [0 if tensor.size == 0 else 1 for tensor in tensors]
-        num_nonempty = numpy.sum(nonempty_tensors)
-        # checking if more than one non-empty tensors are joined.
-        if num_nonempty > 1:
+        # tailing tensors are all tensors except the first one
+        tailing_tensors_are_empty = numpy.all(
+            [tensor.shape[axis] == 0 for tensor in axis_and_tensors[2:]])
+        if tailing_tensors_are_empty:
+            out[0] = tensors[0]
+
+        else:
             ndim = tensors[0].ndim
             if axis < -ndim:
                 raise IndexError("Join axis %d out of bounds [0, %d)" %
@@ -4015,10 +4018,6 @@ class Join(Op):
 
             out[0] = theano._asarray(numpy.concatenate(tensors, axis=axis),
                                      dtype=node.outputs[0].type.dtype)
-        elif num_nonempty == 1:
-            nonempty_tensor_index = numpy.argmax(nonempty_tensors)
-            self.view_map = {0: [nonempty_tensor_index]}
-            out[0] = tensors[nonempty_tensor_index]
 
     def c_code_cache_version(self):
         return