diff --git a/doc/design/simple_op_design.md b/doc/design/simple_op_design.md new file mode 100644 index 0000000000000000000000000000000000000000..49ca5db5da9e400fd2c54eb8903b0dd2eb832d44 --- /dev/null +++ b/doc/design/simple_op_design.md @@ -0,0 +1,201 @@ +## Interaction between C++ and Python + +Users employ API in Python to describe their own network, however, the network construction actually happens in C++. so Protobuf is introduced to send the message between Python and C++. + +The Interaction between Python and C++ can be simplified as two steps: + +1. C++ tells Python how many Ops there are, and what parameter do users need to offer to initialize a new Op. Python then builds API for each Op at compile time. + +2. Users invoke APIs built by Python and provide necessary parameters. These parameters will be sent to C++ fo finish Op construction task. + +### Message form C++ to Python + +We define a Protobuf message class `OpProto` to hold message needed in the first step. What should an `OpProto` contain? This question is equivalent to “What message do we need to offer, to build a Python API which is legal and user oriented and can use to describe a whole Op.” + +Following message are necessary: + +1. Op's name, and its simple comment. +2. Input and output variable number; each variable's name, type, and comment. +3. Op's attributes; each attribute includes name, type, comment, **default value** and **value range**. + +So `OpProto` can be defined as follows: + +```proto +enum AttrType { + INT = 1; + FLOAT = 2; + STRING = 3; + INTS = 4; + FLOATS = 5; + STRINGS = 6; +}; + +message AttrValue { + AttrType type = 1; + optional int iv = 2; + optional float fv = 3; + optional string sv = 4; + repeated int ivs = 5; + repeated float fvs = 6; + repeated string svs = 7; +}; + +message AttrProto { + required string name = 1; + required string comment = 2; + required AttrType type = 3; +}; + +message VarProto { + required string name = 1; + required string comment = 2; +}; + +message OpProto { + repeated VarProto inputs = 1; + repeated VarProto outputs = 2; + repeated AttrProto attrs = 3; + required string type = 4; + required string comment = 5; +}; +``` + +To generate Python code automatically: + +```python +def create_python_ops_creatation_functions(): + op_protos = paddle.framework.OpRegistry.get_all_op_proto() + for type_name in op_protos: + op_proto = op_protos[type_name] + def __impl__(**kwargs): # User must use key word args in Paddle API + inputs = [kwargs.get(ipt.name, "") for ipt in op_proto.inputs] + outputs = [kwargs.get(opt.name, "") for opt in op_proto.outputs] + attrs = [cast_to_op_attr(attr, kwargs.get(attr.name, None)) for attr in op_proto.attrs] + opdesc = （input, outputs, type_name, attrs） + return paddle.framework.OpRegistry.CreateOp(opdesc) + __impl__.__doc__ = create_doc_string(op_proto) + globals()[type_name] = __impl__ + +create_python_ops_creatation_functions() +``` + +### Message from Python to C++ + +To hold message needed in the above second step, we define Protobuf message class `OpDesc`. It is used to hold user-specified parameters in Op describing. + +```proto +message OpDesc { + required string type = 1; + repeated string inputs = 2; + repeated string outputs = 3; + map attrs = 4; +}; +``` + +## OpProto Register + +Every Op has its own `OpProto`. For using convenience, we need to register them and record all their messages. For each `Op` class, we define a corresponding `OpMaker` class, in whose constructor we implement the `OpProto`'s building process. `OpMaker`'s constructor will be invoked by another function `OpRegistry::RegisterOp()`. + +```cpp +class OpProtoMaker { +public: + OpProtoMaker(OpProto* proto): proto_(proto) {} +protected: + OpProto* proto_; + void AddInput(const std::string& name, const std::string& desc) {...} + void AddAttr(const std::string& name, const std::string& desc, TypeId type) {...} + void AddComment(const std::string& comment) { ... } +}; + +class OpRegistry { +public: + using OpCreator = std::function; + + template + static void RegisterOp(const std::string& name) { + gCreators_[name] = [](const OpDesc& desc) { + return new OpType(desc); + }; + OpProto& opProto = gProtos_[name]; + OpMaker()(&opProto); + } + + static map gCreators_; + static map gProtos_; +}; + +template +class OpRegister { + public: + OpRegister(std::string type) { + OpRegistry::RegisterOp(type); + } +}; + +#define REGISTER_OP(op_class, op_maker_class, type_name) \ + class op_class##Register { \ + private: \ + const static OpRegister<#op_class, #op_maker_class> reg; \ + }; \ + const Register op_class##Register::reg(#type_name); + +class CosineOp { +// ... +} + +struct CosineOpProtoMaker : public OpProtoMaker { + CosineOpProtoMaker(OpProto* proto) : OpProtoMaker(proto) { + AddInput("input", "input of cosine op"); + AddAttr("scale", "scale of cosine op", float).Default(1.0).LargerThan(0.0); + AddType("cos"); + AddComment("This is cos op"); + } +} + +REGISTER_OP(CosineOp, CosineOpProtoMaker, cos); +``` + +In `REGISTER_OP(CosineOp, CosineOpProtoMaker, cos)`, we register not only `CosineOp` but also `CosineOpProto`. As fields of `CosineOpProto`, the default value and value range of `scale` are also registered here. + +## Python API + +Python APIs are divided into two types, high-level API and low-level API. + +### High-Level API + +High-level API is called by users directly, so it should keep its style consistent with existing V2 APIs. + +Here is a sample about how a define a fc layer: + +```python +hd = fc_layer(input=data, size=56, with_bias=True, activation="sigmoid"); +``` + +`hd` is the output of `fc_layer` and it's a `variable`. It can be further sent into other layers as input. + +The definition of `fc_layer()`: + +```python +def fc_layer(input, size, with_bias, activation): + attr_map = {"size":size} + check_attrs(attr_map) + w = make_variable('w') + if with_bias: + b = make_variable('b') + else: + b = None + fc_output = make_variable('fc_output'); + fc_op(input, w, b, fc_output, attr_map) + act_output = make_variable('sigmod_output'); + if activation == "sigmod": + sigmod_op(fc_output, act_output); + elif: + # ... + return act_output; +``` + +### Low Leval API + +In above sample, `fc_op` and `sigmod_op` are low-level API. They build `OpDesc` and invoke corresponding C++ code. + +*TODO*