c – 为什么std :: make_shared <>()的性能比boost :: make_shared()好得多？

2019年8月4日 378次阅读

我一直在做一些现场性能测试

1>std::shared_ptr, std::make_shared based on 'gcc 4.7.2' & 'VC10 implementation' 
2>boost::shared_ptr, boost::make_shared based on boost 1.47

测试结果有点有趣.

1>通常std版本表现更好,但特别是std :: make_shared.为什么？我可以增加升级版本的性能,因为C 11不适用于某些旧项目,因为他们使用旧版本的Visual Studio吗？

下面是我用于测试这些内容的代码段.
NB.你需要手动切换升压和放大性病.
NB. “SimpleMSTimer.hpp”是我的boost ptime的计时器包装器,有点太长了,无法在此发布.但随意使用自己的计时器.任何便携时间都可以.

#include "stdafx.h"
#include <vector>
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost\make_shared.hpp>

#include "SimpleMSTimer.hpp"//my timer wrapper for boost ptime

using namespace std;
using namespace boost;

class Thing
{
public:
    Thing()
    {
    }

    void method (void)
    {
        int i = 5;
    }
};

typedef boost::shared_ptr<Thing> ThingPtr;

void processThing(Thing* thing)
{
    thing->method();
}

//loop1 and loop2 test shared_ptr in the vector container
void loop1(long long num)
{
    cout << "native raw pointer: ";
    vector<Thing> thingPtrs;
    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        Thing thing;
        thingPtrs.push_back(thing);
    }
    thingPtrs.clear();
}

void loop2(long long num)
{
    cout << "native boost::shared_ptr: ";
    vector<ThingPtr> thingPtrs;
    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        ThingPtr p1(new Thing);
        thingPtrs.push_back(p1);
    }
}

void loop3(long long num)
{
    cout << "optimized boost::shared_ptr: ";
    vector<ThingPtr> thingPtrs;

    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        ThingPtr p1 = boost::make_shared<Thing>();
        thingPtrs.push_back(p1);
    }
}


//loop3 and loop4 test shared_ptr in loop
void loop4(long long num)
{
    cout << "native raw pointer: ";
    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        Thing* p1 = new Thing();
        processThing(p1);
        delete p1;
    }
}

void loop5(long long num)
{
    cout << "native boost::shared_ptr: ";
    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        ThingPtr p1(new Thing);
        processThing(p1.get());
    }
}

void loop6(long long num)
{
    cout << "optimized boost::shared_ptr: ";
    YiUtil::MSSegmentTimer segTimer(YiUtil::MSSegmentTimer::MLSEC, std::cout);
    for(int i=0; i< num; i++) {
        ThingPtr p1 = boost::make_shared<Thing>();
        processThing(p1.get());
    }
}

int main() {
    long long num = 10000000;
    cout << "test 1" << endl;
    loop1(num);
    loop2(num);
    loop3(num);

    cout << "test 2"<< endl;
    loop4(num);
    loop5(num);
    loop6(num);

    return 0;
}

VC10编译器在发布模式下,gcc使用标志’-O3’编译,以进行最大化优化.
测试结果：

//VS2010 release mode
//boost
test 1
native raw pointer: SegmentTimer: 15 milliseconds/n
native boost::shared_ptr: SegmentTimer: 3312 milliseconds/n
optimized boost::shared_ptr: SegmentTimer: 3093 milliseconds/n
test 2
native raw pointer: SegmentTimer: 921 milliseconds/n
native boost::shared_ptr: SegmentTimer: 2359 milliseconds/n
optimized boost::shared_ptr: SegmentTimer: 2203 milliseconds/n

//std
test 1
native raw pointer: SegmentTimer: 15 milliseconds/n
native std::shared_ptr: SegmentTimer: 3390 milliseconds/n
optimized std::shared_ptr: SegmentTimer: 2203 milliseconds/n
test 2
native raw pointer: SegmentTimer: 937 milliseconds/n
native std::shared_ptr: SegmentTimer: 2359 milliseconds/n
optimized std::shared_ptr: SegmentTimer: 1343 milliseconds/n
==============================================================================
gcc 4.72 release mode
//boost
test 1
native raw pointer: SegmentTimer: 15 milliseconds/n
native boost::shared_ptr: SegmentTimer: 4874 milliseconds/n
optimized boost::shared_ptr: SegmentTimer: 3687 milliseconds/n
test 2
native raw pointer: SegmentTimer: 1109 milliseconds/n
native boost::shared_ptr: SegmentTimer: 2546 milliseconds/n
optimized boost::shared_ptr: SegmentTimer: 1578 milliseconds/n

//std
test 1
native raw pointer: SegmentTimer: 15 milliseconds/n
native std::shared_ptr: SegmentTimer: 3374 milliseconds/n
optimized std::shared_ptr: SegmentTimer: 2296 milliseconds/n
test 2
native raw pointer: SegmentTimer: 1124 milliseconds/n
native std::shared_ptr: SegmentTimer: 2531 milliseconds/n
optimized std::shared_ptr: SegmentTimer: 1468 milliseconds/n

最佳答案 它们表现得更好,因为Boost版本没有更新为使用rvalue引用,它启用了移动语义.而C 11版本确实使用移动语义.这意味着Boost版本必须更频繁地复制.如果你在一个pre-C 11编译器上进行测试,你的目标库(使用std :: tr1 :: shared_ptr)它们的表现应该更相似.

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