AuroraMiddleware/zstd
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Merge pull request #1153 from facebook/dynThreshold

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changed dynamic fse threshold for offset
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Yann Collet 2018-05-26 08:43:45 -07:00 committed by GitHub
commit bb6eaf6495
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1 changed files with 7 additions and 4 deletions
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11
lib/compress/zstd_compress.c
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@ -1751,8 +1751,6 @@ ZSTD_selectEncodingType(
ZSTD_defaultPolicy_e const isDefaultAllowed,
ZSTD_strategy const strategy)
{
#define MIN_SEQ_FOR_DYNAMIC_FSE 64
#define MAX_SEQ_FOR_STATIC_FSE 1000
ZSTD_STATIC_ASSERT(ZSTD_defaultDisallowed == 0 && ZSTD_defaultAllowed != 0);
if (mostFrequent == nbSeq) {
*repeatMode = FSE_repeat_none;
@ -1769,11 +1767,16 @@ ZSTD_selectEncodingType(
}
if (strategy < ZSTD_lazy) {
if (isDefaultAllowed) {
if ((*repeatMode == FSE_repeat_valid) && (nbSeq < MAX_SEQ_FOR_STATIC_FSE)) {
size_t const staticFse_nbSeq_max = 1000;
size_t const dynamicFse_nbSeq_min = (size_t)1 << defaultNormLog; /* 32 for offset, 64 for lengths */
assert(defaultNormLog >= 5 && defaultNormLog <= 6); /* xx_DEFAULTNORMLOG */
if ( (*repeatMode == FSE_repeat_valid)
&& (nbSeq < staticFse_nbSeq_max) ) {
DEBUGLOG(5, "Selected set_repeat");
return set_repeat;
}
if ((nbSeq < MIN_SEQ_FOR_DYNAMIC_FSE) || (mostFrequent < (nbSeq >> (defaultNormLog-1)))) {
if ( (nbSeq < dynamicFse_nbSeq_min)
|| (mostFrequent < (nbSeq >> (defaultNormLog-1))) ) {
DEBUGLOG(5, "Selected set_basic");
/* The format allows default tables to be repeated, but it isn't useful.
* When using simple heuristics to select encoding type, we don't want