Merge pull request #5089 from lamblin/fix_maxargmax_zero_shape

theano/tensor/basic.py

@@ -1421,8 +1421,10 @@ class MaxAndArgmax(Op):
                                 dtype='int64')
         # Not-reduced axes in front
         transposed_x = numpy.transpose(x, numpy.concatenate((keep_axes, axes)))
-        reshaped_x = transposed_x.reshape(transposed_x.shape[:len(keep_axes)] +
-                                          (-1,))
+        kept_shape = transposed_x.shape[:len(keep_axes)]
+        reduced_shape = transposed_x.shape[len(keep_axes):]
+        new_shape = kept_shape + (numpy.prod(reduced_shape),)
+        reshaped_x = transposed_x.reshape(new_shape)
 
         max_idx[0] = theano._asarray(numpy.argmax(reshaped_x, axis=-1),
                                      dtype='int64')

theano/tensor/tests/test_basic.py

@@ -3083,6 +3083,15 @@ class T_max_and_argmax(unittest.TestCase):
         v = eval_outputs(max_and_argmax(x, [1, -1])[0].shape)
         assert tuple(v) == numpy.max(data, (1, -1)).shape
 
+    def test_zero_shape(self):
+        x = tensor.matrix()
+        m, i = max_and_argmax(x, axis=1)
+        f = theano.function([x], [m, i])
+        xv = numpy.zeros((0, 4), dtype=floatX)
+        mv, iv = f(xv)
+        assert mv.shape == (0,)
+        assert iv.shape == (0,)
+
 
 class T_argmin_argmax(unittest.TestCase):
     def setUp(self):