Fixed crash with Composite support code and GPU

theano/sandbox/cuda/tests/test_basic_ops.py

@@ -410,6 +410,34 @@ def test_elemwise_composite_float64():
                         assert not any([i.type.dtype=='float64' for i in s.inputs+s.outputs])
 
 
+def test_elemwise_composite_support_code():
+    """
+    This was generating an error at compile time.
+    Commit 3d1690fa346103594356ecaeceeb2c6757b45d2b fixed that.
+    """
+    X = tcn.shared_constructor(value=numpy.zeros((100, 10), dtype="float32"),
+                               name='X')
+    W = tcn.shared_constructor(value=numpy.zeros((10, 1), dtype="float32"),
+                               name='W')
+    U = T.dot(X, W)
+    Y = tcn.shared_constructor(value=numpy.zeros((100, 1), dtype="float32"),
+                               name='Y')
+    P = T.exp(-(Y - U) ** 2)
+    epsilon = numpy.asarray(0.001, dtype="float32")
+    NLL = -T.mean(T.log(P + epsilon))  # SupportCodeError
+    G = T.grad(NLL, wrt=[W])
+
+    backup = theano.config.warn.identify_1pexp_bug
+    theano.config.warn.identify_1pexp_bug = False
+    try:
+        f_grad = theano.function(inputs=[], outputs=G, mode=mode_with_gpu)
+    finally:
+        theano.config.warn.identify_1pexp_bug = backup
+    f_grad()
+
+    topo = f_grad.maker.env.toposort()
+    assert sum([isinstance(node.op, T.Elemwise) for node in topo]) == 1
+    assert sum([isinstance(node.op, tcn.GpuElemwise) for node in topo]) == 1
 
 
 def speed_elemwise_collapse():

theano/scalar/basic.py

@@ -2422,10 +2422,11 @@ class Composite(ScalarOp):
         rval = []
         for subnode, subnodename in zip(self.env.toposort(), self.nodenames):
             try:
-                rval.append(
-                        subnode.op.c_support_code_apply(
+                subnode_support_code = subnode.op.c_support_code_apply(
                             subnode,
-                            subnodename % dict(nodename=name)))
+                            subnodename % dict(nodename=name))
+                if subnode_support_code:
+                    rval.append(subnode_support_code)
             except gof.utils.MethodNotDefined:
                 pass
         # there should be no need to remove duplicate code blocks because