Make fusion optimizer faster for big graph.

theano/tensor/opt.py

@@ -3409,6 +3409,8 @@ class FusionOptimizer(Optimizer):
             nodelist.reverse()
             did_something = False
             for node in nodelist:
+                # Don't try to fuse node that have already been fused.
+                if node in env.nodes:
                     new_outputs = self.optimizer(node)
                     if new_outputs:
                         assert len(new_outputs) == len(node.outputs)
@@ -3417,11 +3419,9 @@ class FusionOptimizer(Optimizer):
                                 zip(node.outputs, new_outputs),
                                 reason = self.__class__.__name__)
                             did_something = True
-                        break
                         except InconsistencyError, e:
                             pass
 
-
 if config.tensor.local_elemwise_fusion:
     _logger.debug("enabling optimization fusion elemwise in fast_run")
     compile.optdb.register('elemwise_fusion', FusionOptimizer(local_elemwise_fusion), 71.00, 'fast_run', 'fusion', 'local_elemwise_fusion')