linuxc 函数的耗时测试

最新推荐文章于 2025-10-30 09:48:13 发布

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本文介绍了一种获取当前时间微秒数的方法，并通过两个不同实现方式的斐波那契数列算法，展示了变量定义位置对程序运行效率的影响。通过时间差的测量，对比了两种算法的执行效率。

获取当前时间的微妙

/**
 * 获取当前时间的微妙数
*/
long int GetMicrosecondCount()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return tv.tv_sec*1000000 + tv.tv_usec;
}

获取前后时间差

#define GET_TIME(t, code) { t = GetMicrosecondCount();\
                            code; \
                            t = GetMicrosecondCount() - t;}

测试

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>

#define GET_TIME(t, code) { t = GetMicrosecondCount();\
                            code; \
                            t = GetMicrosecondCount() - t;}

/**
 * 获取当前时间的微妙数
*/
long int GetMicrosecondCount()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    return tv.tv_sec*1000000 + tv.tv_usec;
}

/*temp定义在循环内*/
unsigned long long fibonacci1(unsigned int count)
{
    unsigned long long before = 0, sum = 1;

    if (count < 1){
        return before;
    }
    
    for (int i = 1; i < count; i++){
        unsigned long long temp = before + sum;
        before = sum;
        sum = temp;
    }
    return sum;
}

/*temp定义在循环外*/
unsigned long long fibonacci2(int count)
{
    unsigned long long before = 0, sum = 1;
    unsigned long long temp = 0;
    if (count < 1){
        return before;
    }
    
    for (int i = 1; i < count; i++){
        temp = before + sum;
        before = sum;
        sum = temp;
    }
    return sum;
}

int main(int argc, char * argv[])
{
    unsigned long long sum = 0;   
    long int t = 0; //时间间隔

    if (argc != 2){
        printf("请输入次数\n");
    }
    int count = atoi(argv[1]);

    /*1. 将temp定义在 循环内部*/
    GET_TIME(t, sum = fibonacci1(count););
    printf("t1 = %ld, sum = %llu\n", t, sum);

    /*2. 将temp定义在 循环外部*/
    GET_TIME(t, sum = fibonacci2(count););
    printf("t2 = %ld, sum = %llu\n", t, sum);
}