Question

编辑：永远不要使用DEBUG构建进行分析...一旦切换到RELEASE，就没有明显的延迟，并且时间呈线性变化。创建和删除1000000个对象的时间总计在370毫秒内。

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我有一个包含指向对象指针的地图：std::map<int, DummyObject *> myMap 当我删除地图时，我注意到地图越大似乎需要更长的时间 - 指数级。我期待线性行为。

虽然通过地图进行干式迭代（实际上没有做任何事情）的行为或多或少是线性的，但删除对象（不修改地图!!）完全打破了。有没有人对这种行为有解释？更重要的是：我能做些什么来加快速度？因为不幸的是我真的有一个60000+对象的案例，清理我的地图花了太长时间......

以下是代码：

class DummyObject
{
public:
     DummyObject() {}
    ~DummyObject() {}
};

void testSpeed( int iMapSize )
{
    const unsigned int uiStart = GetTickCount();

    typedef std::map<int, DummyObject *> T_MyMap;
    T_MyMap myMap;

    // Fill the map...
    for( int i = 0; i < iMapSize; i++ ) {
        myMap[i] = new DummyObject();
    }
    const unsigned int uiFilled = GetTickCount();

    // Dry iteration through the map...
    for( T_MyMap::const_iterator it = myMap.begin(); it != myMap.end(); it++ ) {
        int i = 0;  // do something
    }
    const unsigned int uiIterate = GetTickCount();

    // Delete the map...
    for( T_MyMap::const_iterator it = myMap.begin(); it != myMap.end(); it++ ) {
        delete it->second;
    }
    const unsigned int uiDeleted = GetTickCount();

    myMap.clear();
    const unsigned int uiCleared = GetTickCount();

    DebugText( arg( "MapSize: %1 --- ",   iMapSize )
             + arg( "filled:  %1 msecs; ", uiFilled  - uiStart )
             + arg( "iterate: %1 msecs; ", uiIterate - uiFilled )
             + arg( "deleted: %1 msecs; ", uiDeleted - uiIterate )
             + arg( "cleared: %1 msecs; ", uiCleared - uiDeleted )
             + arg( "total:   %1 msecs; ", uiCleared - uiStart ) );
}

我称之为......

testSpeed( 100 );
testSpeed( 1000 );
testSpeed( 10000 );
testSpeed( 100000 );
testSpeed( 1000000 );

...这是我得到的输出：

MapSize:     100 --- filled:      0 msecs; iterate:    0 msecs; deleted:     16 msecs; cleared:    0 msecs; total:       16 msecs;
MapSize:    1000 --- filled:     31 msecs; iterate:    0 msecs; deleted:     15 msecs; cleared:    0 msecs; total:       46 msecs;
MapSize:   10000 --- filled:    203 msecs; iterate:   16 msecs; deleted:     47 msecs; cleared:   15 msecs; total:      281 msecs;
MapSize:  100000 --- filled:   2527 msecs; iterate:  250 msecs; deleted:   1435 msecs; cleared:  234 msecs; total:     4446 msecs;
MapSize: 1000000 --- filled:  34055 msecs; iterate: 2652 msecs; deleted: 172241 msecs; cleared: 1981 msecs; total:   210929 msecs;

为什么不删除std :: map线性时间内的对象？或者：在std :: map中删除对象的最快方法是什么？

0 个答案: