From 1804b8bb85560f0074afda41cfc3998b8e04795f Mon Sep 17 00:00:00 2001 From: Frediano Ziglio Date: Fri, 4 Sep 2015 11:00:18 +0100 Subject: improve performances comparing image pixels This patch contains a bit of small optimizations. It avoid boolean operations which could involve branches replacing with binary operations (equal/all_ident -> some_differences). The other optimization avoids the use of ABS. First the way the macro was used (with a large expression) was not easy to optimize by the compiler. Then instead of using ABS a much simpler range check is used so instead of (ABS(n) >= k) a ((n) <= -k || (n) >= k) is used. This looks small but modern compilers can translate this not in range check in a couple of machine instructions (and a single compare). Using operf on same samples (using spice-server-replay) and trying 2 runs I got run 1 2 ------------------------- before 104441 106267 after 92387 91083 So the performance increase is about 13%. Signed-off-by: Frediano Ziglio Acked-by: Jonathon Jongsma --- server/red_bitmap_utils.h | 41 ++++++++++++++++++++--------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/server/red_bitmap_utils.h b/server/red_bitmap_utils.h index 1c13ced..df13c81 100644 --- a/server/red_bitmap_utils.h +++ b/server/red_bitmap_utils.h @@ -49,6 +49,7 @@ #else #define CONTRAST_TH 8 #endif +#define CONTRASTING(n) ((n) <= -CONTRAST_TH || (n) >= CONTRAST_TH) #define SAMPLE_JUMP 15 @@ -62,29 +63,27 @@ static const double FNAME(PIX_PAIR_SCORE)[] = { // return 0 - equal, 1 - for contrast, 2 for no contrast (PIX_PAIR_SCORE is defined accordingly) static inline int FNAME(pixelcmp)(PIXEL p1, PIXEL p2) { - int diff = ABS(GET_r(p1) - GET_r(p2)); - int equal; + int diff, any_different; - if (diff >= CONTRAST_TH) { + diff = GET_r(p1) - GET_r(p2); + any_different = diff; + if (CONTRASTING(diff)) { return 1; } - equal = !diff; - diff = ABS(GET_g(p1) - GET_g(p2)); - - if (diff >= CONTRAST_TH) { + diff = GET_g(p1) - GET_g(p2); + any_different |= diff; + if (CONTRASTING(diff)) { return 1; } - equal = equal && !diff; - - diff = ABS(GET_b(p1) - GET_b(p2)); - if (diff >= CONTRAST_TH) { + diff = GET_b(p1) - GET_b(p2); + any_different |= diff; + if (CONTRASTING(diff)) { return 1; } - equal = equal && !diff; - if (equal) { + if (!any_different) { return 0; } else { return 2; @@ -93,22 +92,22 @@ static inline int FNAME(pixelcmp)(PIXEL p1, PIXEL p2) static inline double FNAME(pixels_square_score)(PIXEL *line1, PIXEL *line2) { - double ret = 0.0; - int all_ident = TRUE; + double ret; + int any_different = 0; int cmp_res; cmp_res = FNAME(pixelcmp)(*line1, line1[1]); - all_ident = all_ident && (!cmp_res); - ret += FNAME(PIX_PAIR_SCORE)[cmp_res]; + any_different |= cmp_res; + ret = FNAME(PIX_PAIR_SCORE)[cmp_res]; cmp_res = FNAME(pixelcmp)(*line1, *line2); - all_ident = all_ident && (!cmp_res); + any_different |= cmp_res; ret += FNAME(PIX_PAIR_SCORE)[cmp_res]; cmp_res = FNAME(pixelcmp)(*line1, line2[1]); - all_ident = all_ident && (!cmp_res); + any_different |= cmp_res; ret += FNAME(PIX_PAIR_SCORE)[cmp_res]; // ignore squares where all pixels are identical - if (all_ident) { - ret -= (FNAME(PIX_PAIR_SCORE)[0]) * 3; + if (!any_different) { + ret = 0; } return ret; -- cgit v1.2.3