Refactorize framework/*.proto

[wangkuiyi]

Our CMakeLists file contains

proto_library(op_desc SRCS op_desc.proto DEPS attribute_proto)
cc_test(op_proto_test SRCS op_proto_test.cc DEPS op_proto protobuf)
cc_test(op_desc_test SRCS op_desc_test.cc DEPS op_desc protobuf)

cc_library(attribute SRCS attribute.cc DEPS op_desc op_proto)

cc_library(operator SRCS operator.cc DEPS op_desc device_context tensor scope attribute)
cc_test(operator_test SRCS operator_test.cc DEPS operator op_registry)

cc_library(grad_op_builder SRCS grad_op_builder.cc DEPS op_proto operator)
cc_library(op_registry SRCS op_registry.cc DEPS op_desc grad_op_builder)
cc_test(op_registry_test SRCS op_registry_test.cc DEPS op_registry)
cc_test(grad_op_builder_test SRCS grad_op_builder_test.cc DEPS grad_op_builder op_registry add_op)

py_proto_compile(framework_py_proto SRCS attribute.proto op_proto.proto op_desc.proto)

We can see that operator depends on op_desc and attribute, and the latter depends on op_proto as well. As this dependency propagates in following rules, any target that depends on op_desc also depends on op_desc. So we can merged these two proto files together.

[wangkuiyi]

Also both op_desc and op_proto depend on attribute_proto, these three proto files should be merged.

[wangkuiyi]

The current op_proto.proto file contains the following field in message VarProto

message VarProto {
  // Is that input/output could be a list or not.
  // If so, that Op should write a attributed named `input_format` or
  // `output_format`.
  //
  // e.g.
  //   If the op is a fc op, the inputs are `X`, `W`, `b`. The `X` and `W`
  //   could be multiple, so the multiple of `X` and `W` is True, and OpDesc
  //   will hold a attribute of them.
  //
  //   The Op desc of same fc could be
  //   {
  //      "type": "fc",
  //      "input": ["X1", "X2", "W1", "W2", "b"],
  //      "output": "fc.out",
  //      "attrs" : {
  //        "input_format": [0, 2, 4, 5]
  //      }
  //   }
  //
  optional bool multiple = 3 [ default = false ];

I don't understand the meaning of multiple by reading the comment and had to ask @Canpio .

This design is really hacky and far from readable.

I would propose the introduction of

message VarDesc {
  string name = 1;
  int dup = 2 [default = 0];
};

[jacquesqiao]

VarDesc is better than attr of temporary_index