在测试性能时，有时需要测试一段代码的执行时间，下面这段测试代码就能实现该功能。
使用 clock 函数
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// crt_clock.c
// This sample uses clock() to 'sleep' for three
// seconds, then determines how long it takes
// to execute an empty loop 600000000 times.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
// Pauses for a specified number of clock cycles.
void do_sleep( clock_t wait )
{
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
const long num_loops = 600000000L;
int main( void )
{
long i = num_loops;
clock_t start, finish;
double duration;
// Delay for a specified time.
printf( "Delay for three seconds\n" );
do_sleep( (clock_t)3 * CLOCKS_PER_SEC );
printf( "Done!\n" );
// Measure the duration of an event.
start = clock();
while( i-- )
;
finish = clock();
duration = (double)(finish - start) / CLOCKS_PER_SEC;
printf( "Time to do %ld empty loops is ", num_loops );
printf( "%2.3f seconds\n", duration );
}
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使用 difftime 函数
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// crt_clock.c
// This sample uses clock() to 'sleep' for three
// seconds, then determines how long it takes
// to execute an empty loop 600000000 times.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
// Pauses for a specified number of clock cycles.
void do_sleep( clock_t wait )
{
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
const long num_loops = 600000000L;
int main( void )
{
long i = num_loops;
clock_t start, finish;
double duration;
// Delay for a specified time.
printf( "Delay for three seconds\n" );
do_sleep( (clock_t)3 * CLOCKS_PER_SEC );
printf( "Done!\n" );
// Measure the duration of an event.
start = clock();
while( i-- )
;
finish = clock();
duration = (double)(finish - start) / CLOCKS_PER_SEC;
printf( "Time to do %ld empty loops is ", num_loops );
printf( "%2.3f seconds\n", duration );
}
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