ieeetest.c

根据IEEE 1180-1990写的测试iDCT精确性。

/*
 * ieeetest.c --- test IDCT code against the IEEE Std 1180-1990 spec
 *
 * Note that this does only one pass of the test.
 * Six invocations of ieeetest are needed to complete the entire spec.
 * The shell script "doieee" performs the complete test.
 *
 * Written by Tom Lane ([e-mail]).
 * Released to public domain 11/22/93.
 */

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

#include "dct.h"


/* prototypes */

void usage (char *msg);
long ieeerand (long L, long H);
void dct_init(void);
void ref_fdct(DCTELEM block[8][8]);
void ref_idct(DCTELEM block[8][8]);

/* error stat accumulators -- assume initialized to 0 */

long sumerrs[DCTSIZE2];
long sumsqerrs[DCTSIZE2];
int maxerr[DCTSIZE2];


char * meets (double val, double limit)
{
  return ((fabs(val) <= limit) ? "meets" : "FAILS");
}


int
main(int argc, char **argv)
{
  long minpix, maxpix, sign;
  long curiter, niters;
  int i, j;
  double max, total;
  DCTELEM   block[DCTSIZE2];	/* random source data */
  DCTELEM   refcoefs[DCTSIZE2]; /* coefs from reference FDCT */
  DCTELEM   refout[DCTSIZE2];	/* output from reference IDCT */
  DCTELEM   testout[DCTSIZE2]; /* output from test IDCT */

  /* Argument parsing --- not very bulletproof at all */

  if (argc != 5) usage(NULL);

  minpix = atoi(argv[1]);
  maxpix = atoi(argv[2]);
  sign   = atoi(argv[3]);
  niters = atol(argv[4]);

  dct_init();

  /* Loop once per generated random-data block */

  for (curiter = 0; curiter < niters; curiter++) {

    /* generate a pseudo-random block of data */
    for (i = 0; i < DCTSIZE2; i++)
      block[i] = (DCTELEM) (ieeerand(-minpix,maxpix) * sign);

    /* perform reference FDCT */
    memcpy(refcoefs, block, sizeof(DCTELEM)*DCTSIZE2);
    ref_fdct(refcoefs);
    /* clip */
    for (i = 0; i < DCTSIZE2; i++) {
      if (refcoefs[i] < -2048) refcoefs[i] = -2048;
      else if (refcoefs[i] > 2047) refcoefs[i] = 2047;
    }

    /* perform reference IDCT */
    memcpy(refout, refcoefs, sizeof(DCTELEM)*DCTSIZE2);
    ref_idct(refout);
    /* clip */
    for (i = 0; i < DCTSIZE2; i++) {
      if (refout[i] < -256) refout[i] = -256;
      else if (refout[i] > 255) refout[i] = 255;
    }

    /* perform test IDCT */
    memcpy(testout, refcoefs, sizeof(DCTELEM)*DCTSIZE2);
    j_rev_dct(testout);
    /* clip */
    for (i = 0; i < DCTSIZE2; i++) {
      if (testout[i] < -256) testout[i] = -256;
      else if (testout[i] > 255) testout[i] = 255;
    }

    /* accumulate error stats */
    for (i = 0; i < DCTSIZE2; i++) {
      register int err = testout[i] - refout[i];
      sumerrs[i] += err;
      sumsqerrs[i] += err * err;
      if (err < 0) err = -err;
      if (maxerr[i] < err) maxerr[i] = err;
    }

    if (curiter % 100 == 99) {
      fprintf(stderr, ".");
      fflush(stderr);
    }
  }
  fprintf(stderr, "\n");

  /* print results */
  printf("IEEE test conditions: -L = %ld, +H = %ld, sign = %ld, #iters = %ld\n",
	 minpix, maxpix, sign, niters);

  printf("Peak absolute values of errors:\n");
  for (i = 0, j = 0; i < DCTSIZE2; i++) {
    if (j < maxerr[i]) j = maxerr[i];
    printf("%4d", maxerr[i]);
    if ((i%DCTSIZE) == DCTSIZE-1) printf("\n");
  }
  printf("Worst peak error = %d  (%s spec limit 1)\n\n", j,
	 meets((double) j, 1.0));

  printf("Mean square errors:\n");
  max = total = 0.0;
  for (i = 0; i < DCTSIZE2; i++) {
    double err = (double) sumsqerrs[i]  / ((double) niters);
    total += (double) sumsqerrs[i];
    if (max < err) max = err;
    printf(" %8.4f", err);
    if ((i%DCTSIZE) == DCTSIZE-1) printf("\n");
  }
  printf("Worst pmse = %.6f  (%s spec limit 0.06)\n", max, meets(max, 0.06));
  total /= (double) (64*niters);
  printf("Overall mse = %.6f  (%s spec limit 0.02)\n\n", total,
	 meets(total, 0.02));

  printf("Mean errors:\n");
  max = total = 0.0;
  for (i = 0; i < DCTSIZE2; i++) {
    double err = (double) sumerrs[i]  / ((double) niters);
    total += (double) sumerrs[i];
    printf(" %8.4f", err);
    if (err < 0.0) err = -err;
    if (max < err) max = err;
    if ((i%DCTSIZE) == DCTSIZE-1) printf("\n");
  }
  printf("Worst mean error = %.6f  (%s spec limit 0.015)\n", max,
	 meets(max, 0.015));
  total /= (double) (64*niters);
  printf("Overall mean error = %.6f  (%s spec limit 0.0015)\n\n", total,
	 meets(total, 0.0015));

  /* test for 0 input giving 0 output */
  memset(testout, 0, sizeof(DCTELEM)*DCTSIZE2);
  j_rev_dct(testout);
  for (i = 0, j=0; i < DCTSIZE2; i++) {
    if (testout[i]) {
      printf("Position %d of IDCT(0) = %d (FAILS)\n", i, testout[i]);
      j++;
    }
  }
  printf("%d elements of IDCT(0) were not zero\n\n\n", j);

  exit(0);
  return 0;
}


void usage (char *msg)
{
  if (msg != NULL)
    fprintf(stderr, "\nerror: %s\n", msg);

  fprintf(stderr, "\n");
  fprintf(stderr, "usage: ieeetest minpix maxpix sign niters\n");
  fprintf(stderr, "\n");
  fprintf(stderr, "  minpix = -L value per IEEE spec\n");
  fprintf(stderr, "  maxpix =  H value per IEEE spec\n");
  fprintf(stderr, "  sign = +1 for normal, -1 to run negated test\n");
  fprintf(stderr, "  niters = # iterations (10000 for full test)\n");
  fprintf(stderr, "\n");

  exit(1);
}


/* Pseudo-random generator specified by IEEE 1180 */

long ieeerand (long L, long H)
{
  static long randx = 1;
  static double z = (double) 0x7fffffff;

  long i,j;
  double x;

  randx = (randx * 1103515245) + 12345;
  i = randx & 0x7ffffffe;
  x = ((double) i) / z;
  x *= (L+H+1);
  j = x;
  return j-L;
}


/* Reference double-precision FDCT and IDCT */


/* The cosine lookup table */
/* coslu[a][b] = C(b)/2 * cos[(2a+1)b*pi/16] */
double coslu[8][8];


/* Routine to initialise the cosine lookup table */
void dct_init(void)
{
  int a,b;
  double tmp;

  for(a=0;a<8;a++)
    for(b=0;b<8;b++) {
      tmp = cos((double)((a+a+1)*b) * (3.14159265358979323846 / 16.0));
      if(b==0)
	tmp /= sqrt(2.0);
      coslu[a][b] = tmp * 0.5;
    }
}


void ref_fdct (DCTELEM block[8][8])
{
  int x,y,u,v;
  double tmp, tmp2;
  double res[8][8];

  for (v=0; v<8; v++) {
    for (u=0; u<8; u++) {
      tmp = 0.0;
      for (y=0; y<8; y++) {
	tmp2 = 0.0;
	for (x=0; x<8; x++) {
	  tmp2 += (double) block[y][x] * coslu[x][u];
	}
	tmp += coslu[y][v] * tmp2;
      }
      res[v][u] = tmp;
    }
  }

  for (v=0; v<8; v++) {
    for (u=0; u<8; u++) {
      tmp = res[v][u];
      if (tmp < 0.0) {
	x = - ((int) (0.5 - tmp));
      } else {
	x = (int) (tmp + 0.5);
      }
      block[v][u] = (DCTELEM) x;
    }
  }
}


void ref_idct (DCTELEM block[8][8])
{
  int x,y,u,v;
  double tmp, tmp2;
  double res[8][8];

  for (y=0; y<8; y++) {
    for (x=0; x<8; x++) {
      tmp = 0.0;
      for (v=0; v<8; v++) {
	tmp2 = 0.0;
	for (u=0; u<8; u++) {
	  tmp2 += (double) block[v][u] * coslu[x][u];
	}
	tmp += coslu[y][v] * tmp2;
      }
      res[y][x] = tmp;
    }
  }

  for (v=0; v<8; v++) {
    for (u=0; u<8; u++) {
      tmp = res[v][u];
      if (tmp < 0.0) {
	x = - ((int) (0.5 - tmp));
      } else {
	x = (int) (tmp + 0.5);
      }
      block[v][u] = (DCTELEM) x;
    }
  }
}