Ignore unused inputs in some legitimate cases.

theano/compile/builders.py

@@ -59,9 +59,12 @@ class OpFromGraph(gof.Op):
                 if g is None:
                     self.grad_ops.append(lambda *args: None)
                 else:
+                    # It is normal if some inputs are not needed in order
+                    # to compute the gradient, so we ignore them.
                     self.grad_ops.append(OpFromGraph(inputs + output_grads,
                                                      [g],
-                                                     grad_depth = grad_depth - 1))
+                                                     grad_depth = grad_depth - 1,
+                                                     on_unused_input='ignore'))
     def __eq__(self, other):
         #TODO: recognize a copy
         return self is other

theano/compile/module.py

@@ -473,9 +473,9 @@ class Method(Component):
         else:
             effective_mode = self.mode
 
-        #backport
-        #effective_mode = mode if self.mode is None else self.mode
-        rval = F.orig_function(inputs, outputs, effective_mode)
+        # We ignore unused inputs, since all the inputs are passed
+        rval = F.orig_function(inputs, outputs, effective_mode,
+                on_unused_input='ignore')
         memo[self] = rval
         return rval
 

theano/gradient.py

@@ -765,10 +765,11 @@ def verify_grad(fun, pt, n_tests=2, rng=None, eps=None, abs_tol=None,
     def function(inputs, output):
         if mode is None:
             f = compile.function(inputs, output, accept_inplace=True,
-                    allow_input_downcast=True)
+                    allow_input_downcast=True, on_unused_input='ignore')
         else:
             f = compile.function(inputs, output, accept_inplace=True,
-                    allow_input_downcast=True, mode=mode)
+                    allow_input_downcast=True, mode=mode,
+                    on_unused_input='ignore')
         return f
 
     tensor_pt = [TensorType(

theano/scan_module/scan.py

@@ -793,7 +793,8 @@ def scan(fn,
                        dummy_outs,
                        updates=updates,
                        mode=compile.mode.Mode(linker='py',
-                                              optimizer=None))
+                                              optimizer=None),
+                       on_unused_input='ignore')
 
     ##
     ### Step 5. Re-arange inputs of scan into a more strict order

theano/scan_module/scan_op.py

@@ -480,7 +480,8 @@ class Scan(PureOp):
                            wrapped_outputs,
                            mode=self.mode_instance,
                            name=self.name,
-                           profile=profile)
+                           profile=profile,
+                           on_unused_input='ignore')
 
         try:
             cython_mintaps = numpy.asarray(self.mintaps, dtype='int32')