Doing profiles reveals that the check for "is this pixel at end of row?"
if ((cur_pix + 1 - lines) % width == 0)
leads to 2 divisions, one to compute (cur_pix + 1 - lines) (divided by
sizeof(*cur_pix) which could be 3) and one for (x % width).
Although the substituted code looks more long is faster as it does not
involve divisions.
Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx>
---
server/red_bitmap_utils.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/server/red_bitmap_utils.h b/server/red_bitmap_utils.h
index bf82e79..1849588 100644
--- a/server/red_bitmap_utils.h
+++ b/server/red_bitmap_utils.h
@@ -117,7 +117,8 @@ static void FNAME(compute_lines_gradual_score)(PIXEL *lines, int width, int num_
double *o_samples_sum_score, int *o_num_samples)
{
int jump = (SAMPLE_JUMP % width) ? SAMPLE_JUMP : SAMPLE_JUMP - 1;
- PIXEL *cur_pix = lines + width / 2;
+ int cur_x = width / 2;
+ PIXEL *cur_pix = lines + cur_x;
PIXEL *bottom_pix;
PIXEL *last_line = lines + (num_lines - 1) * width;
int num_samples;
@@ -133,13 +134,17 @@ static void FNAME(compute_lines_gradual_score)(PIXEL *lines, int width, int num_
num_samples = 0;
while (cur_pix < last_line) {
- if ((cur_pix + 1 - lines) % width == 0) { // last pixel in the row
+ if (cur_x + 1 == width) { // last pixel in the row
cur_pix--; // jump is bigger than 1 so we will not enter endless loop
+ cur_x--;
}
bottom_pix = cur_pix + width;
samples_sum_score += FNAME(pixels_square_score)(cur_pix, bottom_pix);
num_samples++;
cur_pix += jump;
+ cur_x += jump;
+ while (cur_x >= width)
+ cur_x -= width;
}
(*o_samples_sum_score) = samples_sum_score;
--
2.4.3
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