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[pdiff] Reorganise the inner loops of the convolution.

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Reorder the indices and introduce a couple of temporary accumulators to
improve cache access.
This commit is contained in:
Chris Wilson 2007-10-16 15:29:59 +01:00
parent fa9201b9c9
commit bd3dd72262
1 changed files with 15 additions and 12 deletions
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27
test/pdiff/lpyramid.c
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@ -20,7 +20,7 @@
#include <string.h>
struct _lpyramid {
/* Succesively blurred versions of the original image */
/* Successively blurred versions of the original image */
float *levels[MAX_PYR_LEVELS];
int width;
@ -28,29 +28,32 @@ struct _lpyramid {
};
static void
convolve (lpyramid_t *pyramid, float *a, float *b)
convolve (lpyramid_t *pyramid, float *a, const float *b)
/* convolves image b with the filter kernel and stores it in a */
{
int y,x,i,j,nx,ny;
int y,x,i,j;
const float Kernel[] = {0.05f, 0.25f, 0.4f, 0.25f, 0.05f};
int width = pyramid->width;
int height = pyramid->height;
for (y=0; y<height; y++) {
for (x=0; x<width; x++) {
int index = y * width + x;
a[index] = 0.0f;
for (i=-2; i<=2; i++) {
for (j=-2; j<=2; j++) {
nx=x+i;
ny=y+j;
float sum = 0.f;
for (j=-2; j<=2; j++) {
float sum_i = 0.f;
int ny=y+j;
if (ny<0) ny=-ny;
if (ny>=height) ny=2*height - ny - 1;
ny *= width;
for (i=-2; i<=2; i++) {
int nx=x+i;
if (nx<0) nx=-nx;
if (ny<0) ny=-ny;
if (nx>=width) nx=2*width - nx - 1;
if (ny>=height) ny=2*height - ny - 1;
a[index] += Kernel[i+2] * Kernel[j+2] * b[ny * width + nx];
sum_i += Kernel[i+2] * b[ny + nx];
}
sum += sum_i * Kernel[j+2];
}
*a++ = sum;
}
}
}