Merge pull request #2996 from lamblin/scan_test_values

theano/scan_module/scan_utils.py

@@ -64,6 +64,16 @@ def safe_new(x, tag='', dtype=None):
         else:
             nw_x = x.type()
         nw_x.name = nw_name
+        if theano.config.compute_test_value != 'off':
+            # Copy test value, cast it if necessary
+            try:
+                x_test_value = gof.op.get_test_value(x)
+            except AttributeError:
+                # There is no test value
+                pass
+            else:
+                # This clause is executed if no exception was raised
+                nw_x.tag.test_value = nw_x.type.filter(x_test_value)
         return nw_x
     else:
         try:
@@ -73,11 +83,13 @@ def safe_new(x, tag='', dtype=None):
             # want to avoid the convoluted logic that checks for cuda
             # ndarrays
             pass
+
+    # Cast x if needed. If x has a test value, this will also cast it.
+    if dtype and x.dtype != dtype:
+        x = x.astype(dtype)
+
     nw_x = x.type()
-    if dtype and nw_x.dtype != dtype:
-        nw_x = nw_x.astype(dtype).type()
     nw_x.name = nw_name
-
     # Preserve test values so that the 'compute_test_value' option can be used.
     # The test value is deep-copied to ensure there can be no interactions
     # between test values, due to inplace operations for instance. This may

theano/scan_module/tests/test_scan.py

@@ -4983,12 +4983,34 @@ def test_compute_test_value_grad():
                 )
 
         loss = result_mi[-1]
-        grad = tensor.grad(loss, W_flat)
+        tensor.grad(loss, W_flat)
     finally:
         theano.config.compute_test_value = old_compute_test_val
         theano.config.exception_verbosity = old_exception_verbosity
 
 
+def test_compute_test_value_grad_cast():
+    # Test for test values when variables have to be casted
+    # Reported by Daniel Renshaw at
+    # https://groups.google.com/d/topic/theano-users/o4jK9xDe5WI/discussion
+    backup = theano.config.compute_test_value
+    theano.config.compute_test_value = 'raise'
+    try:
+        h = tensor.matrix('h')
+        h.tag.test_value = numpy.array([[1, 2, 3, 4], [5, 6, 7, 8]],
+                                       dtype=numpy.float64)
+
+        w = theano.shared(numpy.random.randn(4, 3).astype('float64'), name='w')
+
+        outputs, _ = theano.scan(lambda i, h, w: (theano.dot(h[i], w), i),
+                                 outputs_info=[None, 0L], non_sequences=[h, w],
+                                 n_steps=3)
+
+        theano.grad(outputs[0].sum(), w)
+    finally:
+        theano.config.compute_test_value = backup
+
+
 def test_constant_folding_n_steps():
     # The following code used to crash at revision 2060b8f, in the constant
     # folding optimization step.