add executor api

paddle/fluid/train/custom_trainer/feed/executor/executor.h

+#pragma once
+#include <functional>
+#include "paddle/fluid/framework/executor.h"
+#include "paddle/fluid/train/custom_trainer/feed/common/registerer.h"
+#include "paddle/fluid/train/custom_trainer/feed/trainer_context.h"
+
+namespace paddle {
+namespace custom_trainer {
+namespace feed {
+
+class Execute {
+public:
+    Execute() {}
+    virtual ~Execute() {}
+
+    //初始化，包括进行训练网络&配置加载工作
+    virtual int initialize(YAML::Node& exe_config, 
+        std::shared_ptr<TrainerContext> context_ptr) = 0;
+    
+    //scope 可用于填充&取 var
+    virtual ::paddle::framework::Scope* scope() {
+        return &_scope;
+    }
+    //直接取var
+    template <class T>
+    T* var(const std::string& name) {
+        return _scope.Var(name).Get<T>();
+    }
+    template <class T>
+    T* mutable_var(const std::string& name) {
+        return _scope.Var(name)->GetMutable<T>();
+    }
+
+    //执行n轮训练，每轮回调(epoch_id, _scope)
+    virtual int run(uint32_t epoch_num, std::function<void(uint32_t, ::paddle::framework::Scope*)>) = 0;
+    
+protected:
+    ::paddle::framework::Scope _scope;
+};
+REGISTER_REGISTERER(Execute);
+
+class SimpleExecute : public Execute {
+public:
+    SimpleExecute() {}
+    virtual ~SimpleExecute() {}
+    virtual int initialize(YAML::Node& exe_config,
+        std::shared_ptr<TrainerContext> context_ptr);
+    virtual int run(uint32_t epoch_num, std::function<void(uint32_t, ::paddle::framework::Scope*)>) = 0;
+protected:
+    ::paddle::framework::Executor _execute; 
+};
+
+}  // namespace feed
+}  // namespace custom_trainer
+}  // namespace paddle