ddidderr/zstd-rs
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first implementation of small window size for btopt

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noticeably improves compression ratio
when window size is small (< 18).

enwik7	level 19

windowLog	`dev`	`smallwlog`	improvement
23	3.577	3.577	0.02%
22	3.536	3.538	0.06%
21	3.462	3.467	0.14%
20	3.364	3.377	0.39%
19	3.244	3.272	0.86%
18	3.110	3.166	1.80%
17	2.843	3.057	7.53%
16	2.724	2.943	8.04%
15	2.594	2.822	8.79%
14	2.456	2.686	9.36%
13	2.312	2.523	9.13%
12	2.162	2.361	9.20%
11	2.003	2.182	8.94%
This commit is contained in:
Yann Collet
2019-05-31 15:55:12 -07:00
parent b13a9207f9
commit bc601bdc6d
3 changed files with 42 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/compress/zstd_compress.c
+5 -5
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@@ -1387,7 +1387,7 @@ ZSTD_reset_matchState(ZSTD_matchState_t* ms,
note : `params` are assumed fully validated at this stage */
static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
ZSTD_CCtx_params params,
U64 pledgedSrcSize,
U64 const pledgedSrcSize,
ZSTD_compResetPolicy_e const crp,
ZSTD_buffered_policy_e const zbuff)
{
@@ -2868,7 +2868,8 @@ static size_t ZSTD_compress_frameChunk (ZSTD_CCtx* cctx,
ms->dictMatchState = NULL;
}
ZSTD_window_enforceMaxDist(&ms->window, ip + blockSize, maxDist, &ms->loadedDictEnd, &ms->dictMatchState);
//ZSTD_window_enforceMaxDist(&ms->window, ip + blockSize, maxDist, &ms->loadedDictEnd, &ms->dictMatchState);
ZSTD_checkDictValidity(&ms->window, ip + blockSize, maxDist, &ms->loadedDictEnd, &ms->dictMatchState);
/* Ensure hash/chain table insertion resumes no sooner than lowlimit */
if (ms->nextToUpdate < ms->window.lowLimit) ms->nextToUpdate = ms->window.lowLimit;
@@ -3296,12 +3297,11 @@ static size_t ZSTD_compressBegin_internal(ZSTD_CCtx* cctx,
FORWARD_IF_ERROR( ZSTD_resetCCtx_internal(cctx, params, pledgedSrcSize,
ZSTDcrp_continue, zbuff) );
{
size_t const dictID = ZSTD_compress_insertDictionary(
{ size_t const dictID = ZSTD_compress_insertDictionary(
cctx->blockState.prevCBlock, &cctx->blockState.matchState,
&params, dict, dictSize, dictContentType, dtlm, cctx->entropyWorkspace);
FORWARD_IF_ERROR(dictID);
assert(dictID <= (size_t)(U32)-1);
assert(dictID <= UINT32_MAX);
cctx->dictID = (U32)dictID;
}
return 0;