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MSVC8中的SafeCode对性能的影响

Posted on 2007-06-11 10:51 chemz 阅读(2047) 评论(4)  编辑 收藏 引用 所属分类: C++
                          MSVC8中的SafeCode对性能的影响
    由于前面一篇关于编译boost1.34.0编译的blog
http://www.cppblog.com/chemz/archive/2007/06/06/25666.html
中有人提到在Visual C++ 2005中由于微软采用了safe code技术会对性能产生非常大的影
响(下降50%),所以本着性能不可以通过估计和猜测来确定,所以编写了一个针对于此的
测试程序进行了测试。
    该测试程序为了做到足够的覆盖C++标准库中STL部分,所以选择了容器/跌代器/算法三
个关键组成中的具有代表性的类和对象进行了测试。首先解释一下微软所提供的safe code
的目的和作用,由于STL库中为了考虑到性能的最大化所以对于像:边界值检查、合法性检
查以及范围检查等都省略了,此部分需要依靠程序员自行处理,而safe code就是在STL设计
到此部分的代码中添加了判断用的语句(通过宏引入的)。究竟会不会影响到性能呢?有多
大的影响呢?
    测试代码如下:
        #include <iostream>
        #include <ctime>
        #include <vector>
        #include <list>
        #include <map>
        #include <algorithm>
        
        #include <boost/lambda/lambda.hpp>
        #include <boost/lambda/bind.hpp>
       
        #define MAX_TEST_COUNT 1000 * 1000 * 2
        #define TIME_ELAPSE() ( std::clock() - start * 1.0 ) / CLOCKS_PER_SEC
       
        int main( int argc, char *argv[] )
        {
            double times[6];
            size_t idx = 0;
            /*
             * vector
             */
            std::vector<size_t> vec1;
            std::clock_t start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    vec1.push_back( i );
                }
            }
            times[idx++] = TIME_ELAPSE();
       
            std::vector<std::string> vec2;
            start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    vec2.push_back( "std::vector<std::string>" );
                }
            }
            times[idx++] = TIME_ELAPSE();
            /*
             * list
             */
            std::list<size_t> lst1;
            start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    lst1.push_back( i );
                }
            }
            times[idx++] = TIME_ELAPSE();
       
            std::list<std::string> lst2;
            start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    lst2.push_back( "std::vector<std::string>" );
                }
            }
            times[idx++] = TIME_ELAPSE();
            /*
             * map
             */
            std::map<size_t, size_t> map1;
            start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    map1.insert( std::make_pair( i, i ) );
                }
            }
            times[idx++] = TIME_ELAPSE();
       
            std::map<size_t, std::string> map2;
            start = std::clock();
            {
                for ( size_t i = 0; i < MAX_TEST_COUNT; ++i )
                {
                    map2.insert( std::make_pair( i, "std::vector<std::string>" ) );
                }
            }
            times[idx++] = TIME_ELAPSE();
       
            std::cout << "std::vector<size_t>::push_back        " << times[0] << " s" << std::endl;
            std::cout << "std::vector<std::string>::push_back   " << times[1] << " s" << std::endl;
            std::cout << "std::list<size_t>::push_back          " << times[2] << " s" << std::endl;
            std::cout << "std::list<std::string>::push_back     " << times[3] << " s" << std::endl;
            std::cout << "std::map<size_t, size_t>::insert      " << times[4] << " s" << std::endl;
            std::cout << "std::map<size_t, std::string>::insert " << times[5] << " s" << std::endl;
       
            std::cout << std::endl;
            /*
             * iterator
             */
            idx = 0;
            start = std::clock();
            {
                for ( std::vector<size_t>::iterator it = vec1.begin(); it != vec1.end(); ++it )
                {
                    (*it) = (*it) + 1;
                }
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                for ( std::vector<std::string>::iterator it = vec2.begin(); it != vec2.end(); ++it )
                {
                    (*it) = "std::vector<std::string>::iterator";
                }
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                for ( std::list<size_t>::iterator it = lst1.begin(); it != lst1.end(); ++it )
                {
                    (*it) = (*it) + 1;
                }
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                for ( std::list<std::string>::iterator it = lst2.begin(); it != lst2.end(); ++it )
                {
                    (*it) = "std::list<std::string>::iterator";
                }
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                for ( std::map<size_t, size_t>::iterator it = map1.begin(); it != map1.end(); ++it )
                {
                    (*it).second = (*it).second + 1;
                }
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                for ( std::map<size_t, std::string>::iterator it = map2.begin(); it != map2.end(); ++it )
                {
                    (*it).second = "std::map<size_t, std::string>::iterator";
                }
            }
            times[idx++] = TIME_ELAPSE();
       
            std::cout << "std::vector<size_t>::iterator           " << times[0] << " s" << std::endl;
            std::cout << "std::vector<std::string>::iterator      " << times[1] << " s" << std::endl;
            std::cout << "std::list<size_t>::iterator             " << times[2] << " s" << std::endl;
            std::cout << "std::list<std::string>::iterator        " << times[3] << " s" << std::endl;
            std::cout << "std::map<size_t, size_t>::iterator      " << times[4] << " s" << std::endl;
            std::cout << "std::map<size_t, std::string>::iterator " << times[5] << " s" << std::endl;
       
            std::cout << std::endl;
            /*
             * for_each
             */
            using namespace boost::lambda;
            idx = 0;
       
            start = std::clock();
            {
                std::for_each( vec1.begin(), vec1.end(), _1 = _1 + 1 );
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                std::for_each( vec2.begin(), vec2.end(), _1 = "std::for_each" );
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                std::for_each( lst1.begin(), lst1.end(), _1 = _1 + 1 );
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                std::for_each( lst2.begin(), lst2.end(), _1 = "std::for_each" );
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                std::for_each( map1.begin(), map1.end(), bind( &std::map<size_t, size_t>::value_type::second, _1 ) = bind( &std::map<size_t, size_t>::value_type::second, _1 ) + 1 );
            }
            times[idx++] = TIME_ELAPSE();
            start = std::clock();
            {
                std::for_each( map2.begin(), map2.end(), bind( &std::map<size_t, std::string>::value_type::second, _1 ) = "std::for_each" );
            }
            times[idx++] = TIME_ELAPSE();
       
            std::cout << "std::vector<size_t>::for_each           " << times[0] << " s" << std::endl;
            std::cout << "std::vector<std::string>::for_each      " << times[1] << " s" << std::endl;
            std::cout << "std::list<size_t>::for_each             " << times[2] << " s" << std::endl;
            std::cout << "std::list<std::string>::for_each        " << times[3] << " s" << std::endl;
            std::cout << "std::map<size_t, size_t>::for_each      " << times[4] << " s" << std::endl;
            std::cout << "std::map<size_t, std::string>::for_each " << times[5] << " s" << std::endl;
       
            return 0;
        }
    我的测试环境如下:
        软件环境:Visual Studio2005 Pro + SP1, boost1.34.0
        硬件环境:PentiumD 3.0GHz, 4G RAM
    测试数据:
        1. 默认开启safe code
           std::vector<size_t>::push_back        0.031 s
           std::vector<std::string>::push_back   2.609 s
           std::list<size_t>::push_back          0.797 s
           std::list<std::string>::push_back     2.813 s
           std::map<size_t, size_t>::insert      1.906 s
           std::map<size_t, std::string>::insert 4.047 s

           std::vector<size_t>::iterator           0 s
           std::vector<std::string>::iterator      1.718 s
           std::list<size_t>::iterator             0.016 s
           std::list<std::string>::iterator        1.734 s
           std::map<size_t, size_t>::iterator      0.063 s
           std::map<size_t, std::string>::iterator 1.891 s

           std::vector<size_t>::for_each           0.015 s
           std::vector<std::string>::for_each      0.156 s
           std::list<size_t>::for_each             0.016 s
           std::list<std::string>::for_each        0.156 s
           std::map<size_t, size_t>::for_each      0.078 s
           std::map<size_t, std::string>::for_each 0.313 s

        2. 关闭safe code(通过定义如下宏:_CRT_SECURE_NO_DEPRECATE,
                                          _SCL_SECURE_NO_DEPRECATE,
                                          _SECURE_SCL=0)
           std::vector<size_t>::push_back        0.031 s
           std::vector<std::string>::push_back   2.594 s
           std::list<size_t>::push_back          0.796 s
           std::list<std::string>::push_back     2.813 s
           std::map<size_t, size_t>::insert      1.875 s
           std::map<size_t, std::string>::insert 4.047 s

           std::vector<size_t>::iterator           0 s
           std::vector<std::string>::iterator      1.703 s
           std::list<size_t>::iterator             0.031 s
           std::list<std::string>::iterator        1.719 s
           std::map<size_t, size_t>::iterator      0.062 s
           std::map<size_t, std::string>::iterator 1.891 s

           std::vector<size_t>::for_each           0.016 s
           std::vector<std::string>::for_each      0.14 s
           std::list<size_t>::for_each             0.016 s
           std::list<std::string>::for_each        0.172 s
           std::map<size_t, size_t>::for_each      0.062 s
           std::map<size_t, std::string>::for_each 0.313 s

    由上面的测试数据可以的出如下的结论:
    1. safe code对代码的性能确实是有影响的,毕竟加入了判断的代码;
    2. safe code对代码的性能影响非常的小(最大没有超过5%),基本上为了安全型可以
       忽略其影响,如果确实比较注重性能,可以考虑在release版本下关闭safe code检查,
       在debug版下还是打开以发现错误比较好。
 
注:宏解释
    _CRT_SECURE_NO_DEPRECATE和_SCL_SECURE_NO_DEPRECATE用于关闭safe code代码警告;
    _SECURE_SCL用于控制是否采用safe code对STL边界进行检查。

Feedback

# re: MSVC8中的SafeCode对性能的影响  回复  更多评论   

2007-06-11 12:50 by pass86
。NET 2003,应该就没有。

# re: MSVC8中的SafeCode对性能的影响  回复  更多评论   

2007-06-11 13:18 by chemz
是的,safe code是在Visual C++2005以上版本添加上去的。visual C++.NET2003中的STL库已经非常的不错了,标准兼容性也很好。我最开始使用2003的时候使用了STLport4.6.2替换了2003中的STL实现,感觉还不错的

# re: MSVC8中的SafeCode对性能的影响  回复  更多评论   

2007-06-11 14:47 by 空明流转
50%的性能差异是在随即容器随机读写下完成的测试。某牛说。

# re: MSVC8中的SafeCode对性能的影响  回复  更多评论   

2007-10-11 10:06 by 金庆
push_back()是不需要边界检查的,所以性能测试无效:
vec1.push_back( i );

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