inplace elemwise optimizer speed up.

theano/tensor/opt.py

@@ -237,6 +237,11 @@ def inplace_elemwise_optimizer_op(OP):
         else:
             update_outs = []
 
+        protected_inputs = [
+            f.protected for f in fgraph._features if
+            isinstance(f, theano.compile.function_module.Supervisor)]
+        protected_inputs = sum(protected_inputs, [])  # flatten the list
+        protected_inputs.extend(fgraph.outputs)
         for node in list(graph.io_toposort(fgraph.inputs, fgraph.outputs)):
             op = node.op
             # gpuarray GpuElemwise inherit from Elemwise
@@ -245,27 +250,37 @@ def inplace_elemwise_optimizer_op(OP):
             # If big graph and the outputs are scalar, do not make it
             # inplace.
             if (check_each_change != 1 and
-                all([getattr(o.type, 'ndim', -1) == 0
-                     for o in node.outputs])):
+                # If multiple outputs, they must all have the same size,
+                # so only check the first.
+                getattr(node.outputs[0].type, 'ndim', -1) == 0):
                 continue
 
-            baseline = op.inplace_pattern
-            protected_inputs = [
-                f.protected for f in node.fgraph._features if
-                isinstance(f, theano.compile.function_module.Supervisor)]
-            protected_inputs = sum(protected_inputs, [])  # flatten the list
-            protected_inputs.extend(fgraph.outputs)
-            candidate_outputs = [i for i in xrange(len(node.outputs))
-                                 if i not in baseline]
-            # node inputs that are Constant, already destroyed,
-            # fgraph protected inputs and fgraph outputs can't be used as inplace
-            # target.
-            # Remove here as faster.
-            candidate_inputs = [i for i in xrange(len(node.inputs))
-                                if i not in baseline.values() and
-                                not isinstance(node.inputs[i], Constant) and
-                                not fgraph.destroyers(node.inputs[i]) and
-                                node.inputs[i] not in protected_inputs]
+            if op.inplace_pattern:
+                baseline = op.inplace_pattern
+                candidate_outputs = [i for i in xrange(len(node.outputs))
+                                     if i not in baseline]
+                # node inputs that are Constant, already destroyed,
+                # or fgraph protected inputs and fgraph outputs can't be used as
+                # inplace target.
+                # Remove here as faster.
+                candidate_inputs = [i for i in xrange(len(node.inputs))
+                                    if i not in baseline.values() and
+                                    not isinstance(node.inputs[i], Constant) and
+                                    # Is next line costly?
+                                    not fgraph.destroyers(node.inputs[i]) and
+                                    node.inputs[i] not in protected_inputs]
+            else:
+                baseline = []
+                candidate_outputs = list(range(len(node.outputs)))
+                # node inputs that are Constant, already destroyed,
+                # fgraph protected inputs and fgraph outputs can't be used as inplace
+                # target.
+                # Remove here as faster.
+                candidate_inputs = [i for i in xrange(len(node.inputs))
+                                    if not isinstance(node.inputs[i], Constant) and
+                                    not fgraph.destroyers(node.inputs[i]) and
+                                    node.inputs[i] not in protected_inputs]
+
 
             verbose = False