使用Qt中的容器给C++开发带来很大的便利，而且QVector和QMap等容器扩展的一些成员函数也是很方便的。但是Qt的这些容器和STL库的容器比，效率到底怎么样？我就写了几个简单的遍历的例子，测试了QVector、vector等容器的那些方法效率更高。
测试环境：
系统：windows 10
编译器：MingGW mingw5.3.0
Qt版本：5.9.7
硬件：i7 8代，16G内存
一. 测试QVector和vector的各种遍历的方法：
1 void CompareQVectorAndVectorTraverse()
2 {
3 int size = 100000000;
4 QVector<int> qv(size, 1);
5 vector<int> v(size, 1);
6
7 printf("vector size: %d\n", size);
8 // const_iterator比较
9 QVector<int>::ConstIterator cqvit;
10 int sum = 0;
11 qint64 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
12 for( cqvit = qv.constBegin(); cqvit != qv.constEnd(); ++cqvit)
13 {
14 sum += *cqvit;
15 }
16 qint64 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
17 printf( "qvector ConstIterator %dms\n", end - start );
18 printf("%d\n", sum);
19
20 QVector<int>::const_iterator cqvit2;
21 sum = 0;
22 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
23 for( cqvit2 = qv.cbegin(); cqvit2 != qv.cend(); ++cqvit2)
24 {
25 sum += *cqvit2;
26 }
27 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
28 printf( "qvector const_iterator %dms\n", end - start );
29 printf("%d\n", sum);
30
31 vector<int>::const_iterator cvit;
32 sum = 0;
33 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
34 for( cvit = v.cbegin(); cvit != v.cend(); ++cvit )
35 {
36 sum += *cvit;
37 }
38 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
39 printf( "stl vector const_iterator %dms\n", end - start );
40 printf("%d\n", sum);
41
42 // iterator比较
43 QVector<int>::iterator it;
44 sum = 0;
45 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
46 for( it = qv.begin(); it != qv.end(); ++it)
47 {
48 sum += *it;
49 }
50 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
51 printf( "qvector iterator %dms\n", end - start );
52 printf("%d\n", sum);
53
54 vector<int>::iterator vit;
55 sum = 0;
56 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
57 for( vit = v.begin(); vit != v.end(); ++vit )
58 {
59 sum += *vit;
60 }
61 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
62 printf( "stl vector iterator %dms\n", end - start );
63 printf("%d\n", sum);
64
65 //[]比较
66 sum = 0;
67 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
68 for( int i = 0; i < qv.size(); ++i)
69 {
70 sum += qv[i];
71 }
72 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
73 printf( "QVector [] %dms\n", end - start );
74 printf("%d\n", sum);
75
76
77 sum = 0;
78 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
79 for( int i = 0; i < v.size(); ++i)
80 {
81 sum += v[i];
82 }
83 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
84 printf( "stl vector [] %dms\n", end - start );
85 printf("%d\n", sum);
86
87 //.data()比较
88 sum = 0;
89 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
90 int *data = qv.data();
91 for( int i = 0; i < qv.size(); ++i)
92 {
93 sum += data[i];
94 }
95 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
96 printf( "QVector .data() %dms\n", end - start );
97 printf("%d\n", sum);
98
99 sum = 0;
100 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
101 data = v.data();
102 for( int i = 0; i < v.size(); ++i)
103 {
104 sum += data[i];
105 }
106 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
107 printf( "stl vector .data() %dms\n", end - start );
108 printf("%d\n", sum);
109
110 //：比较
111 sum = 0;
112 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
113 for( int val : qv )
114 {
115 sum += val;
116 }
117 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
118 printf( "QVector : %dms\n", end - start );
119 printf("%d\n", sum);
120
121 sum = 0;
122 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
123 for( int val : v)
124 {
125 sum += val;
126 }
127 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
128 printf( "stl vector : %dms\n", end - start );
129 printf("%d\n", sum);
130 }
运行结果：
1 vector size: 100000000 2 qvector ConstIterator 1252ms 3 100000000 4 qvector const_iterator 1254ms 5 100000000 6 stl vector const_iterator 1318ms 7 100000000 8 qvector iterator 4233ms 9 100000000 10 stl vector iterator 1319ms 11 100000000 12 QVector [] 4862ms 13 100000000 14 stl vector [] 456ms 15 100000000 16 QVector .data() 275ms 17 100000000 18 stl vector .data() 296ms 19 100000000 20 QVector : 187ms 21 100000000 22 stl vector : 870ms 23 100000000
二. 测试QMap和map的各种遍历的方法：
1 void CompareQMapAndMapTraverse()
2 {
3 int size = 1000000;
4 qint64 sum = 0;
5 qint64 start, end;
6 map<string, int> m;
7 char *tmps = new char[10];
8 for( int i = 0; i < size; ++i )
9 {
10 sprintf( tmps, "%s%d", "a", i);
11 m.insert( make_pair(tmps, i) );
12 }
13 QMap<string, int> qm(m);
14 printf("map size: %d\n", m.size());
15
16
17 //iterator比较
18 QMap<string, int>::iterator qmit;
19 sum = 0;
20 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
21 for(qmit = qm.begin(); qmit != qm.end(); ++qmit )
22 {
23 sum += qmit.value();
24 }
25 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
26 printf( "QMap iterator %dms\n", end - start );
27 printf("%d\n", sum);
28
29 map<string, int>::iterator mit;
30 sum = 0;
31 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
32 for( mit = m.begin(); mit != m.end(); ++mit )
33 {
34 sum += mit->second;
35 }
36 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
37 printf( "stl::map iterator %dms\n", end - start );
38 printf("%d\n", sum);
39
40 //const_iterator比较
41 QMap<string, int>::const_iterator cqmit;
42 sum = 0;
43 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
44 for(cqmit = qm.cbegin(); cqmit != qm.cend(); ++cqmit )
45 {
46 sum += cqmit.value();
47 }
48 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
49 printf( "QMap const_iterator %dms\n", end - start );
50 printf("%d\n", sum);
51
52 map<string, int>::const_iterator cmit;
53 sum = 0;
54 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
55 for( cmit = m.cbegin(); cmit != m.cend(); ++cmit )
56 {
57 sum += cmit->second;
58 }
59 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
60 printf( "stl::map const_iterator %dms\n", end - start );
61 printf("%d\n", sum);
62
63 QMap<string, int>::key_iterator qmkeyit;
64 sum = 0;
65 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
66 for( qmkeyit = qm.keyBegin(); qmkeyit != qm.keyEnd(); ++qmkeyit )
67 {
68 sum += qm[*qmkeyit];
69 }
70 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
71 printf( "QMap key_iterator %dms\n", end - start );
72 printf("%d\n", sum);
73
74 sum = 0;
75 start = QDateTime::currentDateTime().toMSecsSinceEpoch();
76 for( string k : qm.keys() )
77 {
78 sum += qm[k];
79 }
80 end = QDateTime::currentDateTime().toMSecsSinceEpoch();
81 printf( "QMap .keys %dms\n", end - start );
82 printf("%d\n", sum);
83
84 }
运行结果：
1 map size: 1000000 2 QMap iterator 49ms 3 1783293664 4 stl::map iterator 38ms 5 1783293664 6 QMap const_iterator 33ms 7 1783293664 8 stl::map const_iterator 38ms 9 1783293664 10 QMap key_iterator 407ms 11 1783293664 12 QMap .keys 551ms 13 1783293664
基本和预期的结果差不多，得出结果是QVector最好用for(T &t : qvT)方式。QMap用iterator比较快，而且const_iterator和iterator差不多。
标签：map,end,QMap,iterator,遍历性,sum,start,toMSecsSinceEpoch,printf From： https://www.cnblogs.com/ybqjymy/p/18037751