C语言计算程序运行时间简单实例

ゝ一世哀愁。 2022-10-10 13:55 173阅读 0赞

## 时间函数`clock()` ##

C/C++中的计时函数是`clock()`，与其相关的数据类型是`clock_t`，在标准C/C++中，最小的计时单位是一毫秒.  
`clock_t`是一个长整形数。

typedef long clock_t

在`time.h`文件中，还定义了一个常量`CLOCKS_PER_SEC`，它用来表示一秒钟会有多少个时钟计时单元

#define CLOCKS_PER_SEC ((__clock_t) 1000000)

通过一个简单实例来计算一组循环需要的时间

#include "stdio.h"
    #include "stdlib.h"
    #include "time.h"
    main(){ 
        int i = 0;
        clock_t start_time;
        clock_t finish_time;
        clock_t real_time;
        float current_time;
        float program_time;
    
        start_time=clock();
        current_time=(float)start_time / CLOCKS_PER_SEC;
        printf("Program start time: %f\n",current_time);
    
        for(i=0;i<100;i++){ 
            real_time=clock();
            current_time=((float)real_time / CLOCKS_PER_SEC);
            printf("No.%d Loop Time: %f\n",i,current_time);
        }
        finish_time=clock();
        current_time=(float)finish_time/CLOCKS_PER_SEC;
        printf("Program finish time:%f\n",current_time);
        program_time=(float)(finish_time-start_time)/CLOCKS_PER_SEC;
        printf("Program complete time: %f\n",program_time);
        return 0;
    }

Output
    Program start time: 0.002459
    No.0 Loop Time: 0.002750
    No.1 Loop Time: 0.002788
    No.2 Loop Time: 0.002804
    No.3 Loop Time: 0.002819
    No.4 Loop Time: 0.002834
    No.5 Loop Time: 0.002864
    No.6 Loop Time: 0.002893
    No.7 Loop Time: 0.002922
    No.8 Loop Time: 0.002951
    No.9 Loop Time: 0.002980
    No.10 Loop Time: 0.002995
    No.11 Loop Time: 0.003025
    No.12 Loop Time: 0.003054
    No.13 Loop Time: 0.003083
    No.14 Loop Time: 0.003112
    No.15 Loop Time: 0.003166
    No.16 Loop Time: 0.003191
    No.17 Loop Time: 0.003217
    No.18 Loop Time: 0.003242
    No.19 Loop Time: 0.003267
    No.20 Loop Time: 0.003292
    No.21 Loop Time: 0.003317
    No.22 Loop Time: 0.003343
    No.23 Loop Time: 0.003368
    No.24 Loop Time: 0.003393
    No.25 Loop Time: 0.003417
    No.26 Loop Time: 0.003443
    No.27 Loop Time: 0.003467
    No.28 Loop Time: 0.003492
    No.29 Loop Time: 0.003517
    No.30 Loop Time: 0.003542
    No.31 Loop Time: 0.003568
    No.32 Loop Time: 0.003592
    No.33 Loop Time: 0.003617
    No.34 Loop Time: 0.003642
    No.35 Loop Time: 0.003668
    No.36 Loop Time: 0.003693
    No.37 Loop Time: 0.003718
    No.38 Loop Time: 0.003743
    No.39 Loop Time: 0.003768
    No.40 Loop Time: 0.003793
    No.41 Loop Time: 0.003818
    No.42 Loop Time: 0.003843
    No.43 Loop Time: 0.003868
    No.44 Loop Time: 0.003893
    No.45 Loop Time: 0.003918
    No.46 Loop Time: 0.003943
    No.47 Loop Time: 0.003968
    No.48 Loop Time: 0.003993
    No.49 Loop Time: 0.004018
    No.50 Loop Time: 0.004043
    No.51 Loop Time: 0.004068
    No.52 Loop Time: 0.004093
    No.53 Loop Time: 0.004118
    No.54 Loop Time: 0.004143
    No.55 Loop Time: 0.004168
    No.56 Loop Time: 0.004195
    No.57 Loop Time: 0.004219
    No.58 Loop Time: 0.004245
    No.59 Loop Time: 0.004270
    No.60 Loop Time: 0.004295
    No.61 Loop Time: 0.004320
    No.62 Loop Time: 0.004345
    No.63 Loop Time: 0.004370
    No.64 Loop Time: 0.004395
    No.65 Loop Time: 0.004420
    No.66 Loop Time: 0.004445
    No.67 Loop Time: 0.004470
    No.68 Loop Time: 0.004495
    No.69 Loop Time: 0.004519
    No.70 Loop Time: 0.004544
    No.71 Loop Time: 0.004569
    No.72 Loop Time: 0.004594
    No.73 Loop Time: 0.004618
    No.74 Loop Time: 0.004643
    No.75 Loop Time: 0.004669
    No.76 Loop Time: 0.004693
    No.77 Loop Time: 0.004718
    No.78 Loop Time: 0.004743
    No.79 Loop Time: 0.004768
    No.80 Loop Time: 0.004793
    No.81 Loop Time: 0.004818
    No.82 Loop Time: 0.004843
    No.83 Loop Time: 0.004868
    No.84 Loop Time: 0.004893
    No.85 Loop Time: 0.004918
    No.86 Loop Time: 0.004942
    No.87 Loop Time: 0.004967
    No.88 Loop Time: 0.004992
    No.89 Loop Time: 0.005017
    No.90 Loop Time: 0.005042
    No.91 Loop Time: 0.005067
    No.92 Loop Time: 0.005091
    No.93 Loop Time: 0.005117
    No.94 Loop Time: 0.005142
    No.95 Loop Time: 0.005167
    No.96 Loop Time: 0.005192
    No.97 Loop Time: 0.005217
    No.98 Loop Time: 0.005242
    No.99 Loop Time: 0.005267
    Program finish time:0.005292
    Program complete time: 0.002833