PaddlePaddle算子注册原理阅读记录

PaddlePaddle通过REGISTER_OPERATOR宏来进行算子注册，以paddle/fluid/operators/gru_unit_op.cc为例，其注册代码如下:

REGISTER_OPERATOR(gru_unit,
                  ops::GRUUnitOp,           //在该文件中界说的class
                  ops::GRUUnitOpMaker,      //在该文件中界说的class
                  ops::GRUUnitGradOpMaker<paddle::framework::OpDesc>,   //在该文件中界说的class
                  ops::GRUUnitGradOpMaker<paddle::imperative::OpBase>);

其中ops::GRUUnitOp、ops::GRUUnitOpMaker和ops::GRUUnitGradOpMaker都是在该文件中界说的class。首先看一下REGISTER_OPERATOR宏，其界说如下:

#define REGISTER_OPERATOR(op_type, op_class, ...)                        
  STATIC_ASSERT_GLOBAL_NAMESPACE(                                        
      __reg_op__##op_type,                                               
      "REGISTER_OPERATOR must be called in global namespace");           
  static ::paddle::framework::OperatorRegistrar<op_class, ##__VA_ARGS__> 
      __op_registrar_##op_type##__(#op_type);                            
  int TouchOpRegistrar_##op_type() {                                     
    __op_registrar_##op_type##__.Touch();                                
    return 0;                                                            
  }

注册gru_unit的宏展开后代码如下:

//STATIC_ASSERT_GLOBAL_NAMESPACE检查REGISTER_OPERATOR宏是否在大局空间中被
//运用,假如不是在大局空间中运用则在编译期报错                              
struct __test_global_namespace___reg_op__gru_unit__ {};
static_assert(
    std ::is_same<::__test_global_namespace___reg_op__gru_unit__,
                  __test_global_namespace___reg_op__gru_unit__>::value,
    "REGISTER_OPERATOR must be called in global namespace");
static ::paddle ::framework ::OperatorRegistrar<
    ops ::GRUUnitOp,
    ops ::GRUUnitOpMaker,
    ops ::GRUUnitGradOpMaker<paddle ::framework ::OpDesc>,
    ops ::GRUUnitGradOpMaker<paddle ::imperative ::OpBase>>
    __op_registrar_gru_unit__("gru_unit");
int TouchOpRegistrar_gru_unit() {
  __op_registrar_gru_unit__.Touch();
  return 0;
};

::paddle ::framework ::OperatorRegistrar的界说如下:

class Registrar {
 public:
  // In our design, various kinds of classes, e.g., operators and kernels,
  // have their corresponding registry and registrar. The action of
  // registration is in the constructor of a global registrar variable, which
  // are not used in the code that calls package framework, and would
  // be removed from the generated binary file by the linker. To avoid such
  // removal, we add Touch to all registrar classes and make USE_OP macros to
  // call this method. So, as long as the callee code calls USE_OP, the global
  // registrar variable won't be removed by the linker.
  void Touch() {}
};
template <typename... ARGS>
struct OperatorRegistrar : public Registrar {
  //在构造函数中完成注册
  explicit OperatorRegistrar(const char* op_type) {
    //OpInfoMap主要是一个key为std::string，value为OpInfo的字典，这里要求这个字典之前没有注册该算子
    PADDLE_ENFORCE_EQ(
        OpInfoMap::Instance().Has(op_type),
        false,
        platform::errors::AlreadyExists(
            "Operator '%s' is registered more than once.", op_type));
    static_assert(sizeof...(ARGS) != 0,
                  "OperatorRegistrar should be invoked at least by OpClass");
    OpInfo info;
    details::OperatorRegistrarRecursive<0, false, ARGS...>(op_type, &info); //算子信息写入OpInfo
    OpInfoMap::Instance().Insert(op_type, info); //把OpInfo注册到OpInfoMap
  }
};