LagNonZero_CExample

LagNonZeroExample

#include <iostream>
#include <sys/time.h>                // for gettimeofday()
using namespace std;


double r2()
{
    return (double)rand() / (double)RAND_MAX ;
}

int main() {

    long iter, i;
    double x;
    double elapsedTime;
    double *v;
    double LastVal;
    timeval t1, t2;
    iter = 100000000;
    v = (double *)malloc(sizeof(*v)*iter);

    for ( i = 0; i < iter; i++ )
    {
        x = r2();
        if ( x > 0.5)
        {
            v[i] = x;
        }
        else
        {
            v[i] = 0;
        }
    }

    // start timer
    gettimeofday(&t1, NULL);

    // do stuff
    LastVal = 0;
    for ( i = 0; i < iter; i++ )
    {
        if ( v[i] == 0)
        {
            v[i] = LastVal;
        }
        else
        {
            LastVal = v[i];
        }
    }

    // stop timer
    gettimeofday(&t2, NULL);

    // compute and print the elapsed time in millisec
    elapsedTime = (t2.tv_sec - t1.tv_sec) * 1000.0;      // sec to ms
    elapsedTime += (t2.tv_usec - t1.tv_usec) / 1000.0;   // us to ms
    cout << elapsedTime << " ms.\n";

    for ( i = 0; i < iter; i++ )
    {
        if ( v[i] == 0 )
        {
            printf("v[%lu] = %f\n", i , v[i]);
        }

    }

    return 0;
}