demo.c

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static const char rcsid[] =
    "$Id";

#include "medians_1D.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string.h>
#include <math.h>
#include <float.h>

#define BIG_NUM (1024*1024)

#define MAX_ARRAY_VALUE     1024

#define N_METHODS   5

#define odd(x) ((x)&1)

// Additional required function prototypes
void bench(int, size_t);
int compare(const void *, const void*);
void pixel_qsort(pixelvalue *, int);
pixelvalue median_AHU(pixelvalue *, int);
pixelvalue select_k(int, pixelvalue *, int);

void bench(int verbose, size_t array_size)
{
    int         i;
    int         mednum;
    pixelvalue  med[N_METHODS];

    clock_t     chrono;
    double       elapsed;

    pixelvalue  *   array_init,
                *   array;


    srand48(getpid());

    if (verbose) {
        printf("generating element values...\n");
        fflush(stdout);
    }
    if (array_size<1) array_size = BIG_NUM;

    if (verbose) {
        printf("array size: %ld\n", (long)array_size);
    } else {
        printf("%ld\t", (long)array_size);
    }

    array_init = malloc(array_size * sizeof(pixelvalue));
    array      = malloc(array_size * sizeof(pixelvalue));

    if (array_init==NULL || array==NULL) {
        printf("memory allocation failure: aborting\n");
        return ;
    }

    for (i=0 ; i<array_size; i++) {
        array_init[i] = (pixelvalue)(lrand48() % MAX_ARRAY_VALUE);
    }
    mednum = 0;

    memcpy(array, array_init, array_size * sizeof(pixelvalue));
    if (verbose) {
        printf("quick select    :\t");
        fflush(stdout);
    }
    chrono = clock();
    med[mednum] = quick_select(array, array_size);
    elapsed = (double)(clock() - chrono) / (double)CLOCKS_PER_SEC;
    if (verbose) {
        printf("%5.3f sec\t", elapsed);
        fflush(stdout);
        printf("med %g\n", (double)med[mednum]);
        fflush(stdout);
    } else {
        printf("%5.3f\t", elapsed);
        fflush(stdout);
    }
    mednum++;

    memcpy(array, array_init, array_size * sizeof(pixelvalue));
    if (verbose) {
        printf("Wirth median    :\t");
        fflush(stdout);
    }
    chrono = clock();
    med[mednum] = wirth(array, array_size);
    elapsed = (double)(clock() - chrono) / (double)CLOCKS_PER_SEC;
    if (verbose) {
        printf("%5.3f sec\t", elapsed);
        fflush(stdout);
        printf("med %g\n", (double)med[mednum]);
        fflush(stdout);
    } else {
        printf("%5.3f\t", elapsed);
        fflush(stdout);
    }
    mednum++;

    memcpy(array, array_init, array_size * sizeof(pixelvalue));
    if (verbose) {
        printf("AHU median      :\t");
        fflush(stdout);
    }
    chrono = clock();
    med[mednum] = median_AHU(array, array_size);
    elapsed = (double)(clock() - chrono) / (double)CLOCKS_PER_SEC;
    if (verbose) {
        printf("%5.3f sec\t", elapsed);
        fflush(stdout);
        printf("med %g\n", (double)med[mednum]);
        fflush(stdout);
    } else {
        printf("%5.3f\t", elapsed);
        fflush(stdout);
    }
    mednum++;

    memcpy(array, array_init, array_size * sizeof(pixelvalue));
    if (verbose) {
        printf("torben          :\t");
        fflush(stdout);
    }
    chrono = clock();
    med[mednum] = torben(array, array_size);
    elapsed = (double)(clock() - chrono) / (double)CLOCKS_PER_SEC;
    if (verbose) {
        printf("%5.3f sec\t", elapsed);
        fflush(stdout);
        printf("med %g\n", (double)med[mednum]);
        fflush(stdout);
    } else {
        printf("%5.3f\t", elapsed);
        fflush(stdout);
    }
    mednum++;

    memcpy(array, array_init, array_size * sizeof(pixelvalue));
    if (verbose) {
        printf("fast pixel sort :\t");
        fflush(stdout);
    }
    chrono = clock();
    pixel_qsort(array, array_size);
    elapsed = (double)(clock() - chrono) / (double)CLOCKS_PER_SEC;

    if (odd(array_size)) {
        med[mednum] = array[array_size/2];
    } else {
        med[mednum] = array[(array_size/2) -1];
    }

    if (verbose) {
        printf("%5.3f sec\t", elapsed);
        fflush(stdout);
        printf("med %g\n", (double)med[mednum]);
        fflush(stdout);
    } else {
        printf("%5.3f\t", elapsed);
        fflush(stdout);
    }
    mednum++;

    free(array);
    free(array_init);

    for (i=1 ; i<N_METHODS ; i++) {
        if (fabs(med[i-1] - med[i]) > 10 * FLT_EPSILON) {
            printf("diverging median values!\n");
            fflush(stdout);
        }
    }
    printf("\n");
    fflush(stdout);
    return;
}

int compare(const void *f1, const void *f2)
{ return ( *(pixelvalue*)f1 > *(pixelvalue*)f2) ? 1 : -1 ; }


#define PIX_SWAP(a,b) { pixelvalue temp=(a);(a)=(b);(b)=temp; }
#define PIX_STACK_SIZE 50

void pixel_qsort(pixelvalue *pix_arr, int npix)
{
    int         i,
                ir,
                j,
                k,
                l;
    int *       i_stack;
    int         j_stack;
    pixelvalue  a;

    ir = npix;
    l = 1;
    j_stack = 0;
    i_stack = malloc(PIX_STACK_SIZE * sizeof(pixelvalue));
    for (;;) {
        if (ir-l < 7) {
            for (j=l+1 ; j<=ir ; j++) {
                a = pix_arr[j-1];
                for (i=j-1 ; i>=1 ; i--) {
                    if (pix_arr[i-1] <= a) break;
                    pix_arr[i] = pix_arr[i-1];
                }
                pix_arr[i] = a;
            }
            if (j_stack == 0) break;
            ir = i_stack[j_stack-- -1];
            l  = i_stack[j_stack-- -1];
        } else {
            k = (l+ir) >> 1;
            PIX_SWAP(pix_arr[k-1], pix_arr[l])
            if (pix_arr[l] > pix_arr[ir-1]) {
                PIX_SWAP(pix_arr[l], pix_arr[ir-1])
            }
            if (pix_arr[l-1] > pix_arr[ir-1]) {
                PIX_SWAP(pix_arr[l-1], pix_arr[ir-1])
            }
            if (pix_arr[l] > pix_arr[l-1]) {
                PIX_SWAP(pix_arr[l], pix_arr[l-1])
            }
            i = l+1;
            j = ir;
            a = pix_arr[l-1];
            for (;;) {
                do i++; while (pix_arr[i-1] < a);
                do j--; while (pix_arr[j-1] > a);
                if (j < i) break;
                PIX_SWAP(pix_arr[i-1], pix_arr[j-1]);
            }
            pix_arr[l-1] = pix_arr[j-1];
            pix_arr[j-1] = a;
            j_stack += 2;
            if (j_stack > PIX_STACK_SIZE) {
                printf("stack too small in pixel_qsort: aborting");
                exit(-2001) ;
            }
            if (ir-i+1 >= j-l) {
                i_stack[j_stack-1] = ir;
                i_stack[j_stack-2] = i;
                ir = j-1;
            } else {
                i_stack[j_stack-1] = j-1;
                i_stack[j_stack-2] = l;
                l = i;
            }
        }
    }
    free(i_stack);
}
#undef PIX_STACK_SIZE
#undef PIX_SWAP


pixelvalue select_k(int k, pixelvalue * list, int n)
{
    int             n1 = 0,
                    n2 = 0,
                    n3 = 0;
    pixelvalue  *   S;
    int             i, j;
    pixelvalue      p;

    if (n==1) return list[0];
    p = list[(n>>1)];
    for (i=0 ; i<n ; i++) {
        if (list[i]<p) {
            n1++;
        } else if (fabs(list[i] - p) < 10 * FLT_EPSILON) {
            n2++;
        } else {
            n3++;
        }
    }
    if (n1>=k) {
        S = malloc(n1*sizeof(pixelvalue));
        j = 0;
        for (i=0 ; i<n ; i++) {
            if (list[i]<p) S[j++] = list[i];
        }
        p = select_k(k, S, n1);
        free(S);
    } else {
        if ((n1+n2)<k) {
            S = malloc(n3 * sizeof(pixelvalue));
            j = 0;
            for (i=0 ; i<n ; i++) {
                if (list[i]>p) S[j++] = list[i];
            }
            p = select_k(k-n1-n2, S, n3);
            free(S);
        }
    }
    return p;
}


pixelvalue median_AHU(pixelvalue * list, int n)
{
    if (odd(n)) {
        return select_k((n/2)+1, list, n);
    } else {
        return select_k((n/2), list, n);
    }
}


int main(int argc, char * argv[])
{
    int     i;
    int     from, to, step;
    int     count;

    if (argc<2) {
        printf("usage:\n");
        printf("%s <n>\n", argv[0]);
        printf("\tif n=1 the output is verbose for one attempt\n");
        printf("\tif n>1 the output reads:\n");
        printf("\t# of elements | method1 | method2 | ...\n");
        printf("\n");
        printf("%s <from> <to> <step>\n", argv[0]);
        printf("\twill loop over the number of elements in input\n");
        printf("\n");
        exit(EXIT_FAILURE);
    }

    if (argc==2) {
        count = atoi(argv[1]);
        if (count==1) {
            bench(1, BIG_NUM);
        } else {
            printf("Size\tQS\tWirth\tAHU\tTorben\tpixel sort\n");
            for (i=0 ; i<atoi(argv[1]) ; i++) {
                bench(0, BIG_NUM);
            }
        }
    } else if (argc==4) {
        from = atoi(argv[1]);
        to   = atoi(argv[2]);
        step = atoi(argv[3]);
        for (count=from ; count<=to ; count+=step) {
            bench(0, count);
        }
        return EXIT_SUCCESS;
    }
   return EXIT_SUCCESS;
}