cost_utils.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define NUM_ITERS   1000000

int num_iters = NUM_ITERS;

/* computes min, max, and mean for an array; returns std deviation */
double
do_stats( long long *array, long long *min, long long *max, double *average )
{
    int i;
    double std, tmp;

    *min = *max = array[0];
    *average = 0;
    for ( i = 0; i < num_iters; i++ ) {
        *average += ( double ) array[i];
        if ( *min > array[i] )
            *min = array[i];
        if ( *max < array[i] )
            *max = array[i];
    }
    *average = *average / ( double ) num_iters;
    std = 0;
    for ( i = 0; i < num_iters; i++ ) {
        tmp = ( double ) array[i] - ( *average );
        std += tmp * tmp;
    }
    std = sqrt( std / ( num_iters - 1 ) );
    return ( std );
}

void
do_std_dev( long long *a, int *s, double std, double ave )
{
    int i, j;
    double dev[10];

    for ( i = 0; i < 10; i++ ) {
        dev[i] = std * ( i + 1 );
        s[i] = 0;
    }

    for ( i = 0; i < num_iters; i++ ) {
        for ( j = 0; j < 10; j++ ) {
            if ( ( ( double ) a[i] - dev[j] ) > ave )
                s[j]++;
        }
    }
}

void
do_dist( long long *a, long long min, long long max, int bins, int *d )
{
    int i, j;
    int dmax = 0;
    int range = ( int ) ( max - min + 1 );  /* avoid edge conditions */

    /* clear the distribution array */
    for ( i = 0; i < bins; i++ ) {
        d[i] = 0;
    }

    /* scan the array to distribute cost per bin */
    for ( i = 0; i < num_iters; i++ ) {
        j = ( ( int ) ( a[i] - min ) * bins ) / range;
        d[j]++;
        if ( j && ( dmax < d[j] ) )
            dmax = d[j];
    }

    /* scale each bin to a max of 100 */
    for ( i = 1; i < bins; i++ ) {
        d[i] = ( d[i] * 100 ) / dmax;
    }
}

/* Long Long compare function for qsort */
static int cmpfunc (const void *a, const void *b) {

    if ( *(long long *)a - *(long long *)b < 0 ) {
        return -1;
    }

    if ( *(long long int*)a - *(long long int*)b > 0 ) {
        return 1;
    }

    return 0;
}

/* Calculate the percentiles for making boxplots */
int do_percentile(long long *a,
        long long *percent25,
        long long *percent50,
        long long *percent75,
        long long *percent99) {

    long long *a_sort;
    int i_25,i_50,i_75,i_99;

    /* Allocate room for a copy of the results */
    a_sort = calloc(num_iters,sizeof(long long));
    if (a_sort==NULL) {
        fprintf(stderr,"Memory allocation error!\n");
        return -1;
    }

    /* Make a copy of the results */
    memcpy(a_sort,a,num_iters*sizeof(long long));

    /* Calculate indices */
    i_25=(int)num_iters/4;
    i_50=(int)num_iters/2;
    // index for  75%, not quite accurate because it doesn't
    // take even or odd into consideration
    i_75=(int)num_iters/4*3;
    i_99=(int)num_iters/10*9.9;

    qsort(a_sort,num_iters-1,sizeof(long long),cmpfunc);

    *percent25=a_sort[i_25];
    *percent50=a_sort[i_50];
    *percent75=a_sort[i_75];
    *percent99=a_sort[i_99];

    free(a_sort);

    return 0;
}