lib/zstd
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minor CRatio improvement

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This commit is contained in:
Yann Collet
2015-11-06 18:28:02 +01:00
parent 47cfa9a985
commit 9b8e453713
2 changed files with 18 additions and 11 deletions
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25
lib/zstdhc.c
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@@ -655,6 +655,7 @@ size_t ZSTD_HC_compressBlock_lazy_generic(ZSTD_HC_CCtx* ctx,
/* let's try to find a better solution */ /* let's try to find a better solution */
start = ip; start = ip;
while ((start>anchor) && (start-offset>ctx->base) && (start[-1] == start[-1-offset])) { start--; matchLength++; } /* catch up */
while (ip<ilimit) while (ip<ilimit)
{ {
@@ -670,11 +671,15 @@ size_t ZSTD_HC_compressBlock_lazy_generic(ZSTD_HC_CCtx* ctx,
{ {
size_t offset2=999999; size_t offset2=999999;
size_t ml2 = searchMax(ctx, ip, iend, &offset2, maxSearches, mls); size_t ml2 = searchMax(ctx, ip, iend, &offset2, maxSearches, mls);
int gain2 = (int)(ml2*(3+deep) - ZSTD_highbit((U32)offset2+1)); /* raw approx */ const BYTE* start2 = ip;
int gain1 = (int)(matchLength*(3+deep) - ZSTD_highbit((U32)offset+1) + (3+deep)); int gain1, gain2;
if (ml2)
while ((start2>anchor) && (start2-offset2>ctx->base) && (start2[-1] == start2[-1-offset2])) { start2--; ml2++; } /* catch up */
gain2 = (int)(ml2*(3+deep) - ZSTD_highbit((U32)offset2+1)); /* raw approx */
gain1 = (int)(matchLength*(3+deep) - ZSTD_highbit((U32)offset+1) + (3+deep));
if (gain2 > gain1) if (gain2 > gain1)
{ {
matchLength = ml2, offset = offset2, start = ip; matchLength = ml2, offset = offset2, start = start2;
continue; /* search a better one */ continue; /* search a better one */
} }
} }
@@ -694,12 +699,16 @@ size_t ZSTD_HC_compressBlock_lazy_generic(ZSTD_HC_CCtx* ctx,
{ {
size_t offset2=999999; size_t offset2=999999;
size_t ml2 = searchMax(ctx, ip, iend, &offset2, maxSearches, mls); size_t ml2 = searchMax(ctx, ip, iend, &offset2, maxSearches, mls);
int gain2 = (int)(ml2*4 - ZSTD_highbit((U32)offset2+1)); /* raw approx */ const BYTE* start2 = ip;
int gain1 = (int)(matchLength*4 - ZSTD_highbit((U32)offset+1) + 7); int gain1, gain2;
if (ml2)
while ((start2>anchor) && (start2-offset2>ctx->base) && (start2[-1] == start2[-1-offset2])) { start2--; ml2++; } /* catch up */
gain2 = (int)(ml2*(3+deep) - ZSTD_highbit((U32)offset2+1)); /* raw approx */
gain1 = (int)(matchLength*(3+deep) - ZSTD_highbit((U32)offset+1) + (3+deep));
if (gain2 > gain1) if (gain2 > gain1)
{ {
matchLength = ml2, offset = offset2, start = ip; matchLength = ml2, offset = offset2, start = start2;
continue; continue; /* search a better one */
} }
} }
} }
@@ -707,8 +716,6 @@ size_t ZSTD_HC_compressBlock_lazy_generic(ZSTD_HC_CCtx* ctx,
} }
/* store sequence */ /* store sequence */
if (offset)
while ((start>anchor) && (start-offset>ctx->base) && (start[-1] == start[-1-offset])) { start--; matchLength++; } /* catch up */
{ {
size_t litLength = start - anchor; size_t litLength = start - anchor;
if (offset) offset_1 = offset; if (offset) offset_1 = offset;

4
lib/zstdhc_static.h
View File

@@ -111,8 +111,8 @@ static const ZSTD_HC_parameters ZSTD_HC_defaultParameters[ZSTD_HC_MAX_CLEVEL+1]
{ 21, 17, 20, 3, 5, ZSTD_HC_lazy }, /* level 7 */ { 21, 17, 20, 3, 5, ZSTD_HC_lazy }, /* level 7 */
{ 21, 19, 20, 3, 5, ZSTD_HC_lazy }, /* level 8 */ { 21, 19, 20, 3, 5, ZSTD_HC_lazy }, /* level 8 */
{ 21, 19, 20, 4, 5, ZSTD_HC_lazy }, /* level 9 */ { 21, 19, 20, 4, 5, ZSTD_HC_lazy }, /* level 9 */
{ 21, 19, 20, 5, 5, ZSTD_HC_lazy }, /* level 10 */ { 21, 19, 20, 4, 5, ZSTD_HC_lazy2 }, /* level 10 */
{ 21, 20, 20, 5, 5, ZSTD_HC_lazy }, /* level 11 */ { 21, 20, 21, 4, 5, ZSTD_HC_lazy2 }, /* level 11 */
{ 22, 20, 22, 5, 5, ZSTD_HC_lazy2 }, /* level 12 */ { 22, 20, 22, 5, 5, ZSTD_HC_lazy2 }, /* level 12 */
{ 22, 21, 22, 5, 5, ZSTD_HC_lazy2 }, /* level 13 */ { 22, 21, 22, 5, 5, ZSTD_HC_lazy2 }, /* level 13 */
{ 22, 22, 23, 5, 5, ZSTD_HC_lazy2 }, /* level 14 */ { 22, 22, 23, 5, 5, ZSTD_HC_lazy2 }, /* level 14 */