Crap code performing better than refactored code

turbozedd (153)
Hi guys

I refactored a big mess of a function and for some reason the refactored version is REAAALY slow relative to the messuy one. I expected it to be a little slower because of all the function calls (which should be optimized away by the compiler), but it is much to slow.

I ran both version through gprof but it says they are relatively close in time. Yet I have to wait for the refactored version to finish while the messy version finishes almost instantly.

The same main will exercise both versions.

The clean version (I manually inlined all of my functions):
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#include <cstdio>
#include <cstdlib>
#include <stdint.h>
#include <cmath>

#define RED_OFFSET 0
#define GREEN_OFFSET 1
#define BLUE_OFFSET 2

enum SIGNATURE {
    RGBMEAN, RGBVAR, RGBSKU, RGBKER, RGBVEC,
    RMEAN, RVAR, RSKU, RKER, RVEC,
    GMEAN, GVAR, GSKU, GKER, GVEC,
    BMEAN, BVAR, BSKU, BKER, BVEC
};

void computeSignature(uint8_t *RGBimage, int width, int height, int useEntropy, double *signature);

int main(){
    int i;
    uint8_t data[3000000];
    double signature[20];

     for ( i = 0; i < 3000000; i += 3) {
         data[i] = i;
         data[i + 1] = i % 127;
         data[i + 2] = i * 2;
     }

     ALTcomputeSignature(data, 1000, 1000, 0, signature);
     ALTcomputeSignature(data, 1000, 1000, 1, signature);

    printf("DONE\n");
}

double x_log2_x(uint64_t x){
    return (x==0) ? 0 : (double)x*log2((double)x); //use log(x)/log(2.) if this doesnt work
}

void computeSignature(uint8_t *RGBimage, int width, int height, int useEntropy, double *signature) {
    size_t i;
    size_t size = width*height;
    uint8_t *grayImage = (uint8_t*) malloc(size*sizeof(uint8_t));
    uint8_t *data;

    uint64_t redHistogram[256], greenHistogram[256], blueHistogram[256], grayHistogram[256];
    double  redEntropy[256], greenEntropy[256], blueEntropy[256], grayEntropy[256];

    for(i=0; i<20; i++) signature[i] = 0;

    for(i = 0, data = RGBimage; i < size; i++, data += 3)
        grayImage[i] = (uint8_t) ((double)(data[RED_OFFSET] + data[GREEN_OFFSET] + data[BLUE_OFFSET]) / 3);

    for (i = 0, data = RGBimage; i < size; i++, data += 3){
        grayHistogram[ grayImage[i] ]++;
        redHistogram[ data[ RED_OFFSET ] ]++;
        greenHistogram[ data[ GREEN_OFFSET ] ]++;
        blueHistogram[ data[ BLUE_OFFSET ] ]++;
    }

    if (useEntropy) {
        for (i = 0; i < 256; i++){
            grayEntropy[i] = x_log2_x(grayHistogram[i]);
            redEntropy[i] = x_log2_x(redHistogram[i]);
            greenEntropy[i] = x_log2_x(greenHistogram[i]);
            blueEntropy[i] = x_log2_x(blueHistogram[i]);
        }

        for (i = 0, data = RGBimage; i < size; i++, data += 3) {
            signature[RGBMEAN] += grayEntropy[grayImage[i]];
            signature[RMEAN] += redEntropy[data[RED_OFFSET]];
            signature[GMEAN] += greenEntropy[data[GREEN_OFFSET]];
            signature[BMEAN] += blueEntropy[data[RED_OFFSET]];
        }
        signature[RGBMEAN] /= size;
        signature[RMEAN] /= size;
        signature[GMEAN] /= size;
        signature[BMEAN] /= size;

        for (i = 0, data = RGBimage; i < size; i++, data += 3) {
            signature[RGBVAR] += pow(grayEntropy[grayImage[i]] - signature[RGBMEAN], 2.);
            signature[RVAR] += pow(redEntropy[data[RED_OFFSET]] - signature[RMEAN], 2.);
            signature[GVAR] += pow(greenEntropy[data[GREEN_OFFSET]] - signature[GMEAN], 2.);
            signature[BVAR] += pow(blueEntropy[data[RED_OFFSET]] - signature[BMEAN], 2.);

            signature[RGBSKU] += pow(grayEntropy[grayImage[i]] - signature[RGBMEAN], 3.);
            signature[RSKU] += pow(redEntropy[data[RED_OFFSET]] - signature[RMEAN], 3.);
            signature[GSKU] += pow(greenEntropy[data[GREEN_OFFSET]] - signature[GMEAN], 3.);
            signature[BSKU] += pow(blueEntropy[data[RED_OFFSET]] - signature[BMEAN], 3.);

            signature[RGBKER] += pow(grayEntropy[grayImage[i]] - signature[RGBMEAN], 4.);
            signature[RKER] += pow(redEntropy[data[RED_OFFSET]] - signature[RMEAN], 4.);
            signature[GKER] += pow(greenEntropy[data[GREEN_OFFSET]] - signature[GMEAN], 4.);
            signature[BKER] += pow(blueEntropy[data[RED_OFFSET]] - signature[BMEAN], 4.);
        }

        for (i = 0; i < 256; i++) {
            signature[RGBVEC] += pow(grayEntropy[i], 2.);
            signature[RVEC] += pow(redEntropy[i], 2.);
            signature[GVEC] += pow(greenEntropy[i], 2.);
            signature[BVEC] += pow(blueEntropy[i], 2.);
        }
    }else{
        for (i = 0, data = RGBimage; i < size; i++, data += 3) {
            signature[RGBMEAN] += grayImage[i];
            signature[RMEAN] += data[RED_OFFSET];
            signature[GMEAN] += data[GREEN_OFFSET];
            signature[BMEAN] += data[RED_OFFSET];
        }
        signature[RGBMEAN] /= size;
        signature[RMEAN] /= size;
        signature[GMEAN] /= size;
        signature[BMEAN] /= size;

        for (i = 0, data = RGBimage; i < size; i++, data += 3) {
            signature[RGBVAR] += pow(grayImage[i] - signature[RGBMEAN], 2.);
            signature[RVAR] += pow(data[RED_OFFSET] - signature[RMEAN], 2.);
            signature[GVAR] += pow(data[GREEN_OFFSET] - signature[GMEAN], 2.);
            signature[BVAR] += pow(data[RED_OFFSET] - signature[BMEAN], 2.);

            signature[RGBSKU] += pow(grayImage[i] - signature[RGBMEAN], 3.);
            signature[RSKU] += pow(data[RED_OFFSET] - signature[RMEAN], 3.);
            signature[GSKU] += pow(data[GREEN_OFFSET] - signature[GMEAN], 3.);
            signature[BSKU] += pow(data[RED_OFFSET] - signature[BMEAN], 3.);

            signature[RGBKER] += pow(grayImage[i] - signature[RGBMEAN], 4.);
            signature[RKER] += pow(data[RED_OFFSET] - signature[RMEAN], 4.);
            signature[GKER] += pow(data[GREEN_OFFSET] - signature[GMEAN], 4.);
            signature[BKER] += pow(data[RED_OFFSET] - signature[BMEAN], 4.);
        }

        for (i = 0; i < 256; i++) {
            signature[RGBVEC] += pow(grayHistogram[i], 2.);
            signature[RVEC] += pow(redHistogram[i], 2.);
            signature[GVEC] += pow(greenHistogram[i], 2.);
            signature[BVEC] += pow(blueHistogram[i], 2.);
        }
    }
    signature[RGBVAR] /= size;
    signature[RVAR] /= size;
    signature[GVAR] /= size;
    signature[BVAR] /= size;

    signature[RGBSKU] /= (size * pow(sqrt(signature[RGBVAR]), 3.));
    signature[RSKU] /= (size * pow(sqrt(signature[RVAR]), 3.));
    signature[GSKU] /= (size * pow(sqrt(signature[GVAR]), 3.));
    signature[BSKU] /= (size * pow(sqrt(signature[BVAR]), 3.));

    signature[RGBKER] /= (size * pow(sqrt(signature[RGBVAR]), 4.));
    signature[RKER] /= (size * pow(sqrt(signature[RVAR]), 4.));
    signature[GKER] /= (size * pow(sqrt(signature[GVAR]), 4.));
    signature[BKER] /= (size * pow(sqrt(signature[BVAR]), 4.));

    signature[RGBVEC] = sqrt(signature[RGBVEC]) / (256.0);
    signature[RVEC] = sqrt(signature[RVEC]) / (256.0);
    signature[GVEC] = sqrt(signature[GVEC]) / (256.0);
    signature[BVEC] = sqrt(signature[BVEC]) / (256.0);

    free(grayImage);
}


turbozedd (153)
messy version (be warned, there are many lines of code here that do not contribute):
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void computeSignatureAlternate(uint8_t *dataorg, int width, int height, int roff, int goff, int boff, int option_sig, double *data_sig){
  int i,j;
  int idx;
  long rh[256], gh[256], bh[256],rgbh[256];
  double xre[256], xge[256], xbe[256], xrgbe[256];
  static int *rgbd = NULL;
  long rsum;
  long gsum;
  long bsum;
  double xlog2, dtmp;
  double rgbepnt, rgbevec, rgbevar, rgbesig, rgbesku, rgbeker;
  double repnt, revec, revar, resig, resku, reker;
  double gepnt, gevec, gevar, gesig, gesku, geker;
  double bepnt, bevec, bevar, besig, besku, beker;
  double onethird;
  long rgbsum;
  double remin, remax;
  double gemin, gemax;
  double bemin, bemax;
  double rgbemin, rgbemax;
  static long size;
  uint8_t *data;
  int *ired;
  int *igreen;
  int *iblue;
  double xfac;


  size=width*height;
  rgbd=(int *)malloc(size*sizeof(*rgbd));

  memset(rh, 0, sizeof(rh));
  memset(gh, 0, sizeof(gh));
  memset(bh, 0, sizeof(bh));
  memset(rgbh, 0, sizeof(rgbh));
  memset(xre, 0, sizeof(xre));
  memset(xge, 0, sizeof(xge));
  memset(xbe, 0, sizeof(xbe));
  memset(xrgbe, 0, sizeof(xrgbe));
  // Build Histogram...
  onethird=1.0/3.0;

  //Build the gray scale version of the image
  data=dataorg;
  for(i=0; i<size; i++) {
    // Accumulate blue for grey scale and increment the histogram count
    idx=*(data+boff);
    bh[idx]++;
    rgbd[i] = idx;
    // Accumulate green for grey scale and increment the histogram count
    idx=*(data+1);
    gh[idx]++;
    rgbd[i] += idx;
    // Accumulate red for grey scale and increment the histogram count
    idx=*(data+roff);
    //Increment the histogram and set the intensity to (R+G+B)/3.0
    rh[idx]++;
    rgbd[i] += idx;
    rgbd[i] = (int)(((double)rgbd[i])*onethird);
    rgbh[rgbd[i]]++;
    data += 3;
  }

  rsum=gsum=bsum=size;

  rgbsum=size*3;
  rgbepnt=repnt=gepnt=bepnt=0.0;
  rgbevar=revar=gevar=bevar=0.0;
  rgbesku=resku=gesku=besku=0.0;
  rgbeker=reker=geker=beker=0.0;
  rgbemin=remin=gemin=bemin=1.0e+30;
  rgbemax=remax=gemax=bemax=-1.0e+30;
  data=dataorg;

  xlog2=log10(2.0);
  if(option_sig == 0) {
    // The following is the normalization factor to convert the histogram distribution into a normalized
    //    probability distribution.
    //    xfac=1.0/size;
    xfac=1.0/1.0;
    for (i=0;i<256;i++) {
      xrgbe[i]=(double)rgbh[i]*xfac;
      xre[i]=(double)rh[i]*xfac;
      xge[i]=(double)gh[i]*xfac;
      xbe[i]=(double)bh[i]*xfac;
    }
    for (i=0;i<256;i++) {
      dtmp=(double)(xrgbe[i]);
      xrgbe[i]=-dtmp*log10(1.0/(dtmp+1.0e-100))/xlog2;
      //      printf("Histogram: %d %d %f %f\n",i,rgbh[i],dtmp,xrgbe[i]);
      dtmp=(double)(xre[i]);
      xre[i]=-dtmp*log10(1.0/(dtmp+1.0e-100))/xlog2;
      dtmp=(double)(xge[i]);
      xge[i]=-dtmp*log10(1.0/(dtmp+1.0e-100))/xlog2;
      dtmp=(double)(xbe[i]);
      xbe[i]=-dtmp*log10(1.0/(dtmp+1.0e-100))/xlog2;
    }
  } else {
    for (i=0;i<256;i++) {
      xrgbe[i]=0.0;
    }
  }
  data=dataorg;
  for(i=0; i < size; i++) {
    idx=rgbd[i];
    if(rgbh[idx] > 0) {
      /*      xfac = -table[rgbh[idx]]; */
      if(option_sig == 0) {
	xfac=xrgbe[idx];
      } else {
	xfac=idx;
      }
      rgbepnt = rgbepnt + xfac;
      if (xfac < rgbemin)
	rgbemin=xfac;
      if (xfac > rgbemax)
	rgbemax=xfac;
    }
    idx=*(data+roff);
    if(rh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xre[idx];
      } else {
	xfac=idx;
      }
      repnt+=xfac;
      if (xfac < remin)
	remin=xfac;
      if (xfac > remax)
	remax=xfac;
    }
    idx=*(data+1);
    if(gh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xge[idx];
      } else {
	xfac=idx;
      }
      gepnt+=xfac;
      if(xfac < gemin)
	gemin=xfac;
      if(xfac > gemax)
	gemax=xfac;
    }
    idx=*(data+boff);
    if(bh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xbe[idx];
      } else {
	xfac=idx;
      }
      bepnt+=xfac;
      if(xfac < bemin)
	bemin=xfac;
      if(xfac > bemax)
	bemax=xfac;
    }
    data+=3;
  }

  double rgbemu, remu, gemu, bemu;
  rgbemu=rgbepnt/size;
  remu=repnt/size;
  gemu=gepnt/size;
  bemu=bepnt/size;
  //  printf("Value: %d  %d %f %f %f %f %f\n",option_sig,size,rgbepnt,rgbemu,remu,gemu,bemu);
  //  printf("Value: %f %f\n",rgbemin,rgbemax);
  data=dataorg;
  for(i=0; i < size; i++) {
    idx=rgbd[i];
    if(rgbh[idx] > 0) {
      /*      xfac = -table[rgbh[idx]]; */
      if(option_sig == 0) {
	xfac=xrgbe[idx];
      } else {
	xfac=idx;
      }
      rgbevar+=(xfac-rgbemu)*(xfac-rgbemu);
      rgbesku+=(xfac-rgbemu)*(xfac-rgbemu)*(xfac-rgbemu);
      rgbeker+=(xfac-rgbemu)*(xfac-rgbemu)*(xfac-rgbemu)*(xfac-rgbemu);
      if (xfac < rgbemin)
	rgbemin=xfac;
      if (xfac > rgbemax)
	rgbemax=xfac;
    }
    idx=*(data+roff);
    if(rh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xre[idx];
      } else {
	xfac=idx;
      }
      revar+=(xfac-remu)*(xfac-remu);
      resku+=(xfac-remu)*(xfac-remu)*(xfac-remu);
      reker+=(xfac-remu)*(xfac-remu)*(xfac-remu)*(xfac-remu);
      if (xfac < remin)
	remin=xfac;
      if (xfac > remax)
	remax=xfac;
    }
    idx=*(data+1);
    if(gh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xge[idx];
      } else {
	xfac=idx;
      }
      gevar+=(xfac-gemu)*(xfac-gemu);
      gesku+=(xfac-gemu)*(xfac-gemu)*(xfac-gemu);
      geker+=(xfac-gemu)*(xfac-gemu)*(xfac-gemu)*(xfac-gemu);
      if(xfac < gemin)
	gemin=xfac;
      if(xfac > gemax)
	gemax=xfac;
    }
    idx=*(data+boff);
    if(bh[idx] > 0) {
      /*      xfac = -table[tmp+tmp+tmp]; */
      if(option_sig == 0) {
	xfac=xbe[idx];
      } else {
	xfac=idx;
      }
      bevar+=(xfac-bemu)*(xfac-bemu);
      besku+=(xfac-bemu)*(xfac-bemu)*(xfac-bemu);
      beker+=(xfac-bemu)*(xfac-bemu)*(xfac-bemu)*(xfac-bemu);
      if(xfac < bemin)
	bemin=xfac;
      if(xfac > bemax)
	bemax=xfac;
    }
    data+=3;
  }

  rgbevar=rgbevar/size;
  revar=revar/size;
  gevar=gevar/size;
  bevar=bevar/size;
  rgbesig=sqrt(rgbevar)+1.0e-30;
  resig=sqrt(revar)+1.0e-30;
  gesig=sqrt(gevar)+1.0e-30;
  besig=sqrt(bevar)+1.0e-30;
  rgbesku=rgbesku/(size*rgbesig*rgbesig*rgbesig);
  resku=resku/(size*resig*resig*resig);
  gesku=gesku/(size*gesig*gesig*gesig);
  besku=besku/(size*besig*besig*besig);
  rgbeker=rgbeker/(size*rgbesig*rgbesig*rgbesig*rgbesig);
  reker=reker/(size*resig*resig*resig*resig);
  geker=geker/(size*gesig*gesig*gesig*gesig);
  beker=beker/(size*besig*besig*besig*besig);

  rgbepnt=rgbepnt/(size);
  repnt=repnt/(size);
  gepnt=gepnt/(size);
  bepnt=bepnt/(size);
  
  rgbevec=0.0;
  revec=0.0;
  gevec=0.0;
  bevec=0.0;
  for (i=0;i<256;i++) {
    dtmp=(float)(rgbh[i]);
    if(option_sig == 0) {
      xfac=xrgbe[i];
    } else {
      xfac=dtmp;
    }
    rgbevec+=xfac*xfac;
    dtmp=(float)(rh[i]);
    if(option_sig == 0) {
      xfac=xre[i];
    } else {
      xfac=dtmp;
    }
    revec+=xfac*xfac;
    dtmp=(float)(gh[i]);
    if(option_sig == 0) {
      xfac=xge[i];
    } else {
      xfac=dtmp;
    }
    gevec+=xfac*xfac;
    dtmp=(float)(bh[i]);
    if(option_sig == 0) {
      xfac=xbe[i];
    } else {
      xfac=dtmp;
    }
    bevec+=xfac*xfac;
  }
  rgbevec=sqrt(rgbevec)/(256.0);
  revec=sqrt(revec)/(256.0);
  gevec=sqrt(gevec)/(256.0);
  bevec=sqrt(bevec)/(256.0);

  data_sig[ 0]=rgbepnt;
  data_sig[ 1]=rgbevar;
  data_sig[ 2]=rgbesku;
  data_sig[ 3]=rgbeker;
  data_sig[ 4]=rgbevec;

  data_sig[ 5]=repnt;
  data_sig[ 6]=revar;
  data_sig[ 7]=resku;
  data_sig[ 8]=reker;
  data_sig[ 9]=revec;

  data_sig[10]=gepnt;
  data_sig[11]=gevar;
  data_sig[12]=gesku;
  data_sig[13]=geker;
  data_sig[14]=gevec;

  data_sig[15]=bepnt;
  data_sig[16]=bevar;
  data_sig[17]=besku;
  data_sig[18]=beker;
  data_sig[19]=bevec;
}
Last edited on
jsmith (5804)
At a glance, I see a couple of things:

* You are performing more pow/log function calls (to C library functions) in the new code;
* You are performing 64-bit arithmetic in the new code, but not in the old code.

If you are using a 32-bit OS, be aware that _all_ arithmetic operations on 64-bit types
result in function calls because 64-bit arithmetic has to be done in software rather than
hardware.

Disch (13742)
* You are performing more pow/log function calls (to C library functions) in the new code;


This

For small interger powers (like 2, 3, 4 like you're doing in your code) you're better off manually mutiplying than calling pow(). pow's strength is with abnormal powers (negative, floating point, etc).
turbozedd (153)
Thanks guys.

64-bit is not a problem, but the calls to math.h definitely were.

abnormal numbers... hehe ;)
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