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Merge pull request #1212 from facebook/decSpeed 

Fix decoding speed
dev
Yann Collet 2018-06-27 12:11:45 -07:00 committed by GitHub
parent 5ec2d38870 4489daec09
commit 4746c30001
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 28 additions and 6 deletions
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22
doc/zstd_manual.html
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@ -872,6 +872,28 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
* even when referencing into Dictionary content (default:0) */
ZSTD_p_forceAttachDict, </b>/* ZSTD supports usage of a CDict in-place<b>
* (avoiding having to copy the compression tables
* from the CDict into the working context). Using
* a CDict in this way saves an initial setup step,
* but comes at the cost of more work per byte of
* input. ZSTD has a simple internal heuristic that
* guesses which strategy will be faster. You can
* use this flag to override that guess.
*
* Note that the by-reference, in-place strategy is
* only used when reusing a compression context
* with compatible compression parameters. (If
* incompatible / uninitialized, the working
* context needs to be cleared anyways, which is
* about as expensive as overwriting it with the
* dictionary context, so there's no savings in
* using the CDict by-ref.)
*
* Values greater than 0 force attaching the dict.
* Values less than 0 force copying the dict.
* 0 selects the default heuristic-guided behavior.
*/
} ZSTD_cParameter;
</b></pre><BR>

7
lib/common/entropy_common.c
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@ -85,6 +85,8 @@ size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* t
} }
assert(hbSize >= 4);
/* init */
memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0])); /* all symbols not present in NCount have a frequency of 0 */
bitStream = MEM_readLE32(ip);
nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */
if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
@ -156,11 +158,6 @@ size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSVPtr, unsigned* t
} } /* while ((remaining>1) & (charnum<=*maxSVPtr)) */
if (remaining != 1) return ERROR(corruption_detected);
if (bitCount > 32) return ERROR(corruption_detected);
/* zeroise the rest */
{ unsigned symbNb = charnum;
for (symbNb=charnum; symbNb <= *maxSVPtr; symbNb++)
normalizedCounter[symbNb] = 0;
}
*maxSVPtr = charnum-1;
ip += (bitCount+7)>>3;

5
lib/compress/zstd_compress.c
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@ -1819,8 +1819,11 @@ ZSTD_selectEncodingType(
if (strategy < ZSTD_lazy) {
if (isDefaultAllowed) {
size_t const staticFse_nbSeq_max = 1000;
size_t const dynamicFse_nbSeq_min = (size_t)1 << defaultNormLog; /* 32 for offset, 64 for lengths */
size_t const mult = 10 - strategy;
size_t const baseLog = 3;
size_t const dynamicFse_nbSeq_min = (((size_t)1 << defaultNormLog) * mult) >> baseLog; /* 28-36 for offset, 56-72 for lengths */
assert(defaultNormLog >= 5 && defaultNormLog <= 6); /* xx_DEFAULTNORMLOG */
assert(mult <= 9 && mult >= 7);
if ( (*repeatMode == FSE_repeat_valid)
&& (nbSeq < staticFse_nbSeq_max) ) {
DEBUGLOG(5, "Selected set_repeat");