排序算法总结与测试

本文目录：

1. 总结对比
2. 源码
3. 测试
4. 参考资料

本文主要对常用的排序算法进行测试，分析总结。

1. 总结对比

Wiki 上的总结对比非常详细：

https://en.wikipedia.org/wiki/Sorting_algorithm#Comparison_of_algorithms

2. 源码

项目源码：https://github.com/loverszhaokai/ALG

sort算法源码：https://github.com/loverszhaokai/ALG/blob/master/src/sort.cc

sort算法测试源码：https://github.com/loverszhaokai/ALG/blob/master/test/sort_test.cc

3. 测试

3.1 测试数据

有四组测试数据，如下所示：

    const struct ArrSize arr_sizes [] = {
        { 1000000, 20 },         // 1   million  * 20           = 20  million
        { 10000000, 20 },        // 10  million  * 20           = 200 million

        { 100000, 200 },         // 100 thousand * 200          = 20  million
        { 100000, 2000 },        // 100 thousand * 2000         = 200 million
    };

例如，对于 { 1000000, 20 } 就是100万个大小为20的数组。即 int arr[1000000][20];

该数组中的数据都是随机生成的，代码如下：

static int generate_arrays(int **a, int size_1d, int size_2d)
{
    srand(time(NULL));

    // mod = mod + mod / 2;
    static const int mods[] = { 1, 2, 3, 4, 6, 9, 13, 19, 28, 42, 63, 94,
        141, 211, 316, 474, 711, 1066, 1599, 2398, 3597, 5395, 8092,
        12138, 18207, 27310, 40965, 61447, 92170, 138255, 207382,
        311073,    466609, 699913, 1049869, 1574803, 2362204, 3543306,
        5314959, 7972438, 11958657, 17937985, 26906977, 40360465,
        60540697, 90811045, 136216567, 204324850, 306487275, 459730912,
        689596368, 1034394552 };

    int mi;

    for (int iii = 0; iii < size_1d; iii++) {
        for (int jjj = 0; jjj < size_2d; jjj++) {
            mi = rand() % (sizeof(mods) / sizeof(mods[0]));
            a[iii][jjj] = rand() % mods[mi];
        }
    }

    return 0;
}

3.2 测试方法

1. 先随机生成一个数组 array_orig[size_1d][size_2d]; 如上例，size_1d 就是100万，size_2d就是20。

2. 将该数组拷贝一份 array_expected[size_1d][size_2d]; 然后使用STL sort对该数组进行排序。该数组就是排好序的。

3. 测试sort算法，比如bubble_sort()

3.1 将array_orig[size_1d][size_2d] 拷贝一份 array[size_1d][size_2d]；

3.2 使用bubble_sort() 对array[size_1d][size_2d]进行排序

3.3 比较array[size_1d][size_2d] 和 array_expected[size_1d][size_2d] 是否相等。

代码如下：

typedef void (* SortFunction)(int a[], const int size);

static int test_sort(const char *function_name, SortFunction sort_f)
{
    TimeUtil tu;
    int **array;

    if (copy_arrays(&array, array_orig, size_1d, size_2d) != 0)
        goto err;

    // Run
    tu.restart();

    for (int iii = 0; iii < size_1d; iii++)
        sort_f(array[iii], size_2d);

    tu.stop();

    if (compare_array(array, array_expected, size_1d, size_2d) != 0)
        goto err;

    cout << std::setw(20) << function_name
        << std::setw(10) << "  total run time = "
        << std::setw(10) << (int)tu.get_total_run_time() << " ms"
        << std::setw(18) << " when arrays is: "
        << std::setw(12) << size_1d << " * " << size_2d << endl;

    free_arrays(array, size_1d);
    return 0;

err:
    free_arrays(array, size_1d);
    return -1;
}

3.3 测试数据

/*
Test data:
It takes 664.014 ms to generate arrays: 1000000 * 20
    TEST_insert_sort  total run time =        183 ms  when arrays is:      1000000 * 20
       TEST_stl_sort  total run time =        245 ms  when arrays is:      1000000 * 20
     TEST_quick_sort  total run time =        310 ms  when arrays is:      1000000 * 20
    TEST_select_sort  total run time =        411 ms  when arrays is:      1000000 * 20
     TEST_merge_sort  total run time =        483 ms  when arrays is:      1000000 * 20
    TEST_bubble_sort  total run time =        530 ms  when arrays is:      1000000 * 20

It takes 6642.19 ms to generate arrays: 10000000 * 20
    TEST_insert_sort  total run time =       1862 ms  when arrays is:     10000000 * 20
       TEST_stl_sort  total run time =       2446 ms  when arrays is:     10000000 * 20
     TEST_quick_sort  total run time =       3071 ms  when arrays is:     10000000 * 20
    TEST_select_sort  total run time =       4106 ms  when arrays is:     10000000 * 20
     TEST_merge_sort  total run time =       4791 ms  when arrays is:     10000000 * 20
    TEST_bubble_sort  total run time =       5324 ms  when arrays is:     10000000 * 20

It takes 801.532 ms to generate arrays: 100000 * 200
    TEST_insert_sort  total run time =        665 ms  when arrays is:       100000 * 200
       TEST_stl_sort  total run time =        431 ms  when arrays is:       100000 * 200
     TEST_quick_sort  total run time =        513 ms  when arrays is:       100000 * 200
    TEST_select_sort  total run time =       1578 ms  when arrays is:       100000 * 200
     TEST_merge_sort  total run time =        756 ms  when arrays is:       100000 * 200
    TEST_bubble_sort  total run time =       3317 ms  when arrays is:       100000 * 200

It takes 9591.41 ms to generate arrays: 100000 * 2000
    TEST_insert_sort  total run time =      52265 ms  when arrays is:       100000 * 2000
       TEST_stl_sort  total run time =       5953 ms  when arrays is:       100000 * 2000
     TEST_quick_sort  total run time =       7375 ms  when arrays is:       100000 * 2000
    TEST_select_sort  total run time =     112452 ms  when arrays is:       100000 * 2000
     TEST_merge_sort  total run time =      10539 ms  when arrays is:       100000 * 2000
    TEST_bubble_sort  total run time =     236275 ms  when arrays is:       100000 * 2000

sort_test.cc  total run time=482889 ms
*/

3.4 结果分析

1. 当数组大小较小时，例如20，插入排序是最优的

2. 当数组大小较大时，STL sort排序是最优的。（STL sort还有待研究。。）