Add local_zero_div to specialize phase

theano/tensor/nnet/tests/test_nnet.py

@@ -30,7 +30,8 @@ from theano.tensor.nnet import (categorical_crossentropy,
                                 Prepend_scalar_to_each_row,
                                 relu,
                                 h_softmax,
-                                elu)
+                                elu,
+                                binary_crossentropy)
 from theano.tensor import matrix, vector, lvector, scalar
 
 
@@ -1684,3 +1685,15 @@ def test_elu():
     for alpha in 1.5, 2, -1, -1.5, -2:
         y = elu(x, alpha).eval({x: X})
         utt.assert_allclose(y, numpy.where(X > 0, X, alpha * (numpy.exp(X) - 1)))
+
+
+def test_binary_crossentropy_reshape():
+    # Reported as https://github.com/Theano/Theano/issues/4086
+    a = tensor.tensor4('a')
+    c = binary_crossentropy(sigmoid(a.reshape((-1, 1))), 1).sum()
+    ga = theano.grad(c, a)
+    # This only works when "specialize" options are included
+    mode = theano.compile.get_default_mode().including('fast_run')
+    fga = theano.function([a], ga, mode=mode)
+    utt.assert_allclose(fga(numpy.array([[[[30.]]]], dtype=config.floatX)),
+                        numpy.zeros((1, 1, 1, 1), dtype=config.floatX))

theano/tensor/opt.py

@@ -5270,6 +5270,7 @@ def local_intdiv_by_one(node):
 
 
 @register_canonicalize
+@register_specialize
 @gof.local_optimizer([T.int_div, T.true_div])
 def local_zero_div(node):
     """0 / x -> 0