allow to repeatedly share and update BuildStrategy

test=develop

paddle/fluid/framework/details/build_strategy.cc

@@ -79,9 +79,15 @@ class ParallelExecutorPassBuilder : public ir::PassBuilder {
   BuildStrategy strategy_;
 };
 
-std::shared_ptr<ir::PassBuilder> BuildStrategy::CreatePassesFromStrategy()
-    const {
+std::shared_ptr<ir::PassBuilder> BuildStrategy::CreatePassesFromStrategy(
+    bool from_user) const {
+  if (finalized_by_user_) {
+    return pass_builder_;
+  }
   pass_builder_.reset(new ParallelExecutorPassBuilder(*this));
+  if (from_user) {
+    finalized_by_user_ = true;
+  }
   return pass_builder_;
 }
 
@@ -95,10 +101,8 @@ std::unique_ptr<ir::Graph> BuildStrategy::Apply(
 #else
     const bool use_cuda) const {
 #endif
-  // Create a default one if not initialized by user.
-  if (!pass_builder_) {
-    CreatePassesFromStrategy();
-  }
+  // Create a default one if not finalized by user.
+  CreatePassesFromStrategy(false);
 
   std::unique_ptr<ir::Graph> graph(new ir::Graph(main_program));
 

paddle/fluid/framework/details/build_strategy.h

@@ -80,7 +80,8 @@ struct BuildStrategy {
   // from python side.
   // A new PassBuilder is created based on configs defined above and
   // passes are owned by the PassBuilder.
-  std::shared_ptr<ir::PassBuilder> CreatePassesFromStrategy() const;
+  std::shared_ptr<ir::PassBuilder> CreatePassesFromStrategy(
+      bool from_user) const;
 
   // Apply the passes built by the pass_builder_. The passes will be
   // applied to the Program and output an ir::Graph.
@@ -97,6 +98,7 @@ struct BuildStrategy {
 #endif
 
  private:
+  mutable bool finalized_by_user_ = false;
   mutable std::shared_ptr<ir::PassBuilder> pass_builder_;
 };
 

paddle/fluid/pybind/pybind.cc

@@ -855,10 +855,13 @@ All parameter, weight, gradient are variables in Paddle.
           R"DOC(The type is BOOL, fuse_elewise_add_act_ops indicate whether
                      to fuse elementwise_add_op and activation_op,
                      it may make the execution faster. Default False)DOC")
-      .def("_create_passes_from_strategy",
+      .def("_finalize_strategy_and_create_passes",
            [](BuildStrategy &self) -> std::shared_ptr<ir::PassBuilder> {
-             return self.CreatePassesFromStrategy();
-           });
+             return self.CreatePassesFromStrategy(true);
+           },
+           R"DOC(Allow user to customized passes. Normally model-specific
+                optimization passes should be defined in this way. BuildStrategy
+                cannot be updated after being finalized.)DOC");
 
   pe.def(py::init<const std::vector<platform::Place> &,
                   const std::unordered_set<std::string> &,

python/paddle/fluid/tests/unittests/test_pass_builder.py

@@ -94,7 +94,7 @@ class TestPassBuilder(unittest.TestCase):
 
     def test_parallel_testing_with_new_strategy(self):
         build_strategy = fluid.BuildStrategy()
-        pass_builder = build_strategy._create_passes_from_strategy()
+        pass_builder = build_strategy._finalize_strategy_and_create_passes()
         origin_len = len(pass_builder.all_passes())
 
         viz_pass = pass_builder.append_pass("graph_viz_pass")