busy_work.c

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

/* Repeat doing some busy-work floating point */
/* Until at least len seconds have passed */

double
do_cycles( int minimum_time )
{
    struct timeval start, now;
    double x, sum;

    gettimeofday( &start, NULL );

    for ( ;; ) {
        sum = 1.0;
        for ( x = 1.0; x < 250000.0; x += 1.0 ) {
            sum += x;
        }
        if ( sum < 0.0 ) {
            printf( "==>>  SUM IS NEGATIVE !!  <<==\n" );
        }

        gettimeofday( &now, NULL );
        if ( now.tv_sec >= start.tv_sec + minimum_time ) {
            break;
        }
    }
    return sum;
}