caffe源码学习之Proto数据格式【１】

前言：

　　由于业务需要，接触caffe已经有接近半年，一直忙着阅读各种论文，重现大大小小的模型.　期间也总结过一些caffe源码学习笔记，断断续续，这次打算系统的记录一下caffe源码学习笔记，巩固一下C++，同时也梳理一下自己之前的理解。

正文：

　　我们先不看caffe的框架结构，先介绍一下caffe.proto，是google开源的一种数据交互格式－－Ｇoogle Protobuf,这种数据的格式,我们可以看到caffe.proto中内容：

syntax = "proto2";

package caffe;　//caffe.prto中的各个结构封装在caffe包中，可以通过using namespace caffe; 或者caffe::**　调用

// Specifies the shape (dimensions) of a Blob.
message BlobShape {
repeated int64 dim = 1 [packed = true];
}

message BlobProto {
optional BlobShape shape = 7;
repeated float data = 5 [packed = true];
repeated float diff = 6 [packed = true];
repeated double double_data = 8 [packed = true];
repeated double double_diff = 9 [packed = true];

// 4D dimensions -- deprecated.  Use "shape" instead.
optional int32 num = 1 [default = 0];
optional int32 channels = 2 [default = 0];
optional int32 height = 3 [default = 0];
optional int32 width = 4 [default = 0];
}

.......

当我们在编译完成caffe之后，会自动在src/caffe/proto中生成两个文件caffe.pb.h 和caffe.pb.cc

那么这种数据格式在程序中是如何被使用的呢？　我们举一个简单的例子,来演示caffe.proto生成caffe.pb.h和caffe.pb.cc以及被调用的过程

如果你之前能够编译caffe成功，则说明你已经成功安装了Protobuf,那么我简单的编写一个使用Protobuf的例子吧.

我们先编写一个文件caffe.proto:

package caffe;
message student
{
required int32 age = 1; //ID　required 表示必要字段
required string name = 2; //str　必要字段
optional int32 grade = 3 ; //optional field　可选字段，可以有无，最多ｂ
}

然后我们执行如下操作。

protoc -I=. --cpp_out=. ./caffe.proto

protobuf会自动生成.cc和.h文件

// Generated by the protocol buffer compiler.  DO NOT EDIT!
// source: caffe.proto

#define INTERNAL_SUPPRESS_PROTOBUF_FIELD_DEPRECATION
#include "caffe.pb.h"

#include <algorithm>

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/once.h>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/wire_format_lite_inl.h>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/generated_message_reflection.h>
#include <google/protobuf/reflection_ops.h>
#include <google/protobuf/wire_format.h>
// @@protoc_insertion_point(includes)

namespace caffe {

namespace {

const ::google::protobuf::Descriptor* student_descriptor_ = NULL;
const ::google::protobuf::internal::GeneratedMessageReflection*
student_reflection_ = NULL;

}  // namespace

void protobuf_AssignDesc_caffe_2eproto() {
protobuf_AddDesc_caffe_2eproto();
const ::google::protobuf::FileDescriptor* file =
::google::protobuf::DescriptorPool::generated_pool()->FindFileByName(
"caffe.proto");
GOOGLE_CHECK(file != NULL);
student_descriptor_ = file->message_type(0);
static const int student_offsets_[3] = {
GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(student, age_),
GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(student, name_),
GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(student, grade_),
};
student_reflection_ =
new ::google::protobuf::internal::GeneratedMessageReflection(
student_descriptor_,
student::default_instance_,
student_offsets_,
GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(student, _has_bits_[0]),
GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(student, _unknown_fields_),
-1,
::google::protobuf::DescriptorPool::generated_pool(),
::google::protobuf::MessageFactory::generated_factory(),
sizeof(student));
}

namespace {

GOOGLE_PROTOBUF_DECLARE_ONCE(protobuf_AssignDescriptors_once_);
inline void protobuf_AssignDescriptorsOnce() {
::google::protobuf::GoogleOnceInit(&protobuf_AssignDescriptors_once_,
&protobuf_AssignDesc_caffe_2eproto);
}

void protobuf_RegisterTypes(const ::std::string&) {
protobuf_AssignDescriptorsOnce();
::google::protobuf::MessageFactory::InternalRegisterGeneratedMessage(
student_descriptor_, &student::default_instance());
}

}  // namespace

void protobuf_ShutdownFile_caffe_2eproto() {
delete student::default_instance_;
delete student_reflection_;
}

void protobuf_AddDesc_caffe_2eproto() {
static bool already_here = false;
if (already_here) return;
already_here = true;
GOOGLE_PROTOBUF_VERIFY_VERSION;

::google::protobuf::DescriptorPool::InternalAddGeneratedFile(
"\n\013caffe.proto\022\005caffe\"3\n\007student\022\013\n\003age\030\001"
" \002(\005\022\014\n\004name\030\002 \002(\t\022\r\n\005grade\030\003 \001(\005", 73);
::google::protobuf::MessageFactory::InternalRegisterGeneratedFile(
"caffe.proto", &protobuf_RegisterTypes);
student::default_instance_ = new student();
student::default_instance_->InitAsDefaultInstance();
::google::protobuf::internal::OnShutdown(&protobuf_ShutdownFile_caffe_2eproto);
}

// Force AddDescriptors() to be called at static initialization time.
struct StaticDescriptorInitializer_caffe_2eproto {
StaticDescriptorInitializer_caffe_2eproto() {
protobuf_AddDesc_caffe_2eproto();
}
} static_descriptor_initializer_caffe_2eproto_;

// ===================================================================

#ifndef _MSC_VER
const int student::kAgeFieldNumber;
const int student::kNameFieldNumber;
const int student::kGradeFieldNumber;
#endif  // !_MSC_VER

student::student()
: ::google::protobuf::Message() {
SharedCtor();
}

void student::InitAsDefaultInstance() {
}

student::student(const student& from)
: ::google::protobuf::Message() {
SharedCtor();
MergeFrom(from);
}

void student::SharedCtor() {
_cached_size_ = 0;
age_ = 0;
name_ = const_cast< ::std::string*>(&::google::protobuf::internal::kEmptyString);
grade_ = 0;
::memset(_has_bits_, 0, sizeof(_has_bits_));
}

student::~student() {
SharedDtor();
}

void student::SharedDtor() {
if (name_ != &::google::protobuf::internal::kEmptyString) {
delete name_;
}
if (this != default_instance_) {
}
}

void student::SetCachedSize(int size) const {
GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
_cached_size_ = size;
GOOGLE_SAFE_CONCURRENT_WRITES_END();
}
const ::google::protobuf::Descriptor* student::descriptor() {
protobuf_AssignDescriptorsOnce();
return student_descriptor_;
}

const student& student::default_instance() {
if (default_instance_ == NULL) protobuf_AddDesc_caffe_2eproto();
return *default_instance_;
}

student* student::default_instance_ = NULL;

student* student::New() const {
return new student;
}

void student::Clear() {
if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
age_ = 0;
if (has_name()) {
if (name_ != &::google::protobuf::internal::kEmptyString) {
name_->clear();
}
}
grade_ = 0;
}
::memset(_has_bits_, 0, sizeof(_has_bits_));
mutable_unknown_fields()->Clear();
}

bool student::MergePartialFromCodedStream(
::google::protobuf::io::CodedInputStream* input) {
#define DO_(EXPRESSION) if (!(EXPRESSION)) return false
::google::protobuf::uint32 tag;
while ((tag = input->ReadTag()) != 0) {
switch (::google::protobuf::internal::WireFormatLite::GetTagFieldNumber(tag)) {
// required int32 age = 1;
case 1: {
if (::google::protobuf::internal::WireFormatLite::GetTagWireType(tag) ==
::google::protobuf::internal::WireFormatLite::WIRETYPE_VARINT) {
DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<
::google::protobuf::int32, ::google::protobuf::internal::WireFormatLite::TYPE_INT32>(
input, &age_)));
set_has_age();
} else {
goto handle_uninterpreted;
}
if (input->ExpectTag(18)) goto parse_name;
break;
}

// required string name = 2;
case 2: {
if (::google::protobuf::internal::WireFormatLite::GetTagWireType(tag) ==
::google::protobuf::internal::WireFormatLite::WIRETYPE_LENGTH_DELIMITED) {
parse_name:
DO_(::google::protobuf::internal::WireFormatLite::ReadString(
input, this->mutable_name()));
::google::protobuf::internal::WireFormat::VerifyUTF8String(
this->name().data(), this->name().length(),
::google::protobuf::internal::WireFormat::PARSE);
} else {
goto handle_uninterpreted;
}
if (input->ExpectTag(24)) goto parse_grade;
break;
}

// optional int32 grade = 3;
case 3: {
if (::google::protobuf::internal::WireFormatLite::GetTagWireType(tag) ==
::google::protobuf::internal::WireFormatLite::WIRETYPE_VARINT) {
parse_grade:
DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<
::google::protobuf::int32, ::google::protobuf::internal::WireFormatLite::TYPE_INT32>(
input, &grade_)));
set_has_grade();
} else {
goto handle_uninterpreted;
}
if (input->ExpectAtEnd()) return true;
break;
}

default: {
handle_uninterpreted:
if (::google::protobuf::internal::WireFormatLite::GetTagWireType(tag) ==
::google::protobuf::internal::WireFormatLite::WIRETYPE_END_GROUP) {
return true;
}
DO_(::google::protobuf::internal::WireFormat::SkipField(
input, tag, mutable_unknown_fields()));
break;
}
}
}
return true;
#undef DO_
}

void student::SerializeWithCachedSizes(
::google::protobuf::io::CodedOutputStream* output) const {
// required int32 age = 1;
if (has_age()) {
::google::protobuf::internal::WireFormatLite::WriteInt32(1, this->age(), output);
}

// required string name = 2;
if (has_name()) {
::google::protobuf::internal::WireFormat::VerifyUTF8String(
this->name().data(), this->name().length(),
::google::protobuf::internal::WireFormat::SERIALIZE);
::google::protobuf::internal::WireFormatLite::WriteString(
2, this->name(), output);
}

// optional int32 grade = 3;
if (has_grade()) {
::google::protobuf::internal::WireFormatLite::WriteInt32(3, this->grade(), output);
}

if (!unknown_fields().empty()) {
::google::protobuf::internal::WireFormat::SerializeUnknownFields(
unknown_fields(), output);
}
}

::google::protobuf::uint8* student::SerializeWithCachedSizesToArray(
::google::protobuf::uint8* target) const {
// required int32 age = 1;
if (has_age()) {
target = ::google::protobuf::internal::WireFormatLite::WriteInt32ToArray(1, this->age(), target);
}

// required string name = 2;
if (has_name()) {
::google::protobuf::internal::WireFormat::VerifyUTF8String(
this->name().data(), this->name().length(),
::google::protobuf::internal::WireFormat::SERIALIZE);
target =
::google::protobuf::internal::WireFormatLite::WriteStringToArray(
2, this->name(), target);
}

// optional int32 grade = 3;
if (has_grade()) {
target = ::google::protobuf::internal::WireFormatLite::WriteInt32ToArray(3, this->grade(), target);
}

if (!unknown_fields().empty()) {
target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
unknown_fields(), target);
}
return target;
}

int student::ByteSize() const {
int total_size = 0;

if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
// required int32 age = 1;
if (has_age()) {
total_size += 1 +
::google::protobuf::internal::WireFormatLite::Int32Size(
this->age());
}

// required string name = 2;
if (has_name()) {
total_size += 1 +
::google::protobuf::internal::WireFormatLite::StringSize(
this->name());
}

// optional int32 grade = 3;
if (has_grade()) {
total_size += 1 +
::google::protobuf::internal::WireFormatLite::Int32Size(
this->grade());
}

}
if (!unknown_fields().empty()) {
total_size +=
::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
unknown_fields());
}
GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
_cached_size_ = total_size;
GOOGLE_SAFE_CONCURRENT_WRITES_END();
return total_size;
}

void student::MergeFrom(const ::google::protobuf::Message& from) {
GOOGLE_CHECK_NE(&from, this);
const student* source =
::google::protobuf::internal::dynamic_cast_if_available<const student*>(
&from);
if (source == NULL) {
::google::protobuf::internal::ReflectionOps::Merge(from, this);
} else {
MergeFrom(*source);
}
}

void student::MergeFrom(const student& from) {
GOOGLE_CHECK_NE(&from, this);
if (from._has_bits_[0 / 32] & (0xffu << (0 % 32))) {
if (from.has_age()) {
set_age(from.age());
}
if (from.has_name()) {
set_name(from.name());
}
if (from.has_grade()) {
set_grade(from.grade());
}
}
mutable_unknown_fields()->MergeFrom(from.unknown_fields());
}

void student::CopyFrom(const ::google::protobuf::Message& from) {
if (&from == this) return;
Clear();
MergeFrom(from);
}

void student::CopyFrom(const student& from) {
if (&from == this) return;
Clear();
MergeFrom(from);
}

bool student::IsInitialized() const {
if ((_has_bits_[0] & 0x00000003) != 0x00000003) return false;

return true;
}

void student::Swap(student* other) {
if (other != this) {
std::swap(age_, other->age_);
std::swap(name_, other->name_);
std::swap(grade_, other->grade_);
std::swap(_has_bits_[0], other->_has_bits_[0]);
_unknown_fields_.Swap(&other->_unknown_fields_);
std::swap(_cached_size_, other->_cached_size_);
}
}

::google::protobuf::Metadata student::GetMetadata() const {
protobuf_AssignDescriptorsOnce();
::google::protobuf::Metadata metadata;
metadata.descriptor = student_descriptor_;
metadata.reflection = student_reflection_;
return metadata;
}

// @@protoc_insertion_point(namespace_scope)

}  // namespace caffe

// @@protoc_insertion_point(global_scope)

caffe.pb.cc
生成之后，我们编写一个读取文件caffeReader.cpp

#include "caffe.pb.h"
#include<iostream>
#include<ios>

using namespace std;

void InfoStudents(const caffe::student & stu){
cout<< "student info:"<<endl;
cout<<"name: "<<stu.name()<<endl;
cout<<"age: "<<stu.age()<<endl;
cout<<"grade: "<<stu.grade()<<endl;
}

int main(void)
{
caffe::student stu;
stu.set_age(18);
stu.set_name("gongxijun");
stu.set_grade(146);
InfoStudents(stu);
return 0;
}

编译完成之后，我们执行如下命令：

g++ caffeRead.cpp -o caffeReader caffe.pb.cc -I /usr/local/protobuf/include -L /usr/local/protobuf/lib -lprotobuf -pthread

生成二进制执行文件caffeReader.我们运行该文件就会显示如下信息：



知道了proto文件是如何使用之，再去caffe.proto中看看caffe中定义的结构体：

message 表示需要传输的的参数的结构体.

caffe.proto中保存的有二进制大文件Blob的结构信息：BlobProto, BlobProtoVector, Datum

BlobProto：　

// Specifies the shape (dimensions) of a Blob.
//用来表示图片的shape
message BlobShape {
repeated int64 dim = 1 [packed = true];
}

message BlobProto {
optional BlobShape shape = 7; //现在用来替换下面的num,channels ,height,width,推荐使用
repeated float data = 5 [packed = true]; //forward计算数据
repeated float diff = 6 [packed = true]; //backward的残差数据
repeated double double_data = 8 [packed = true]; //双精度forward计算数据
repeated double double_diff = 9 [packed = true]; //双精度backward的残差数据

// 4D dimensions -- deprecated.  Use "shape" instead.
optional int32 num = 1 [default = 0]; //　图片个数or 维度
optional int32 channels = 2 [default = 0]; //通过比如rgb便是３维
optional int32 height = 3 [default = 0]; //图片高度
optional int32 width = 4 [default = 0]; //图片宽度
}

BlobProtoVector：BlobProto的动态数组

message BlobProtoVector {
repeated BlobProto blobs = 1;
}

Datum是lmdb的数据格式，详情可以看这里　http://blog.csdn.net/u010668907/article/details/51834411

message Datum {//lmdb中的数据格式
optional int32 channels = 1;//图片通道数比如rgb的通道数为3
optional int32 height = 2;//图片的高度
optional int32 width = 3;//图片的宽度
// the actual image data, in bytes
optional bytes data = 4;//图片的数据.比如rgb的三维数组格式
optional int32 label = 5;//这张图片对应的标签,或者这块图像对应的标签[比如20个分类转换成数字之后对应的[0~19]
// Optionally, the datum could also hold float data.
repeated float float_data = 6;//图片的数据,有时候图片在转换过程中会变成浮点型
// If true data contains an encoded image that need to be decoded
optional bool encoded = 7 [default = false];//是否需要解码
}

剩下的大部分都是Layer部分和Net部分和Solver部分的参数，关于Blob和Layer,Net还有Solver这四个部分的关系:

blob作为贯穿整个框架的数据单元，Sovler通过sovler.prototxt【我觉得我可能需要说明一下：.proto和.prototxt的区别吧，这两个都是google protobuff的文件，.proto用来定义结构体参数，.prototxt用来相应的.proto中的结构体的初始化数据】配置初始化Net，然后Net通过调用trainval.prototxt这些参数，来调用对应的Layer，并将数据blob输入到相应的Layer中，Layer来对流入的数据进行计算处理，然后再将计算后的blob数据返回，通过Net流向下一个Layer,每次执行一次,Solver就会计数一次，然后调整learn_rate,descay_weith等权值,参考的是caffe论坛上的这个话题：这里附上链接

http://www.caffecn.cn/?/question/123&sort_key=agree_count&sort=DESC