ddidderr/zstd-rs
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removed frequency booster for stat initialization of btultra2

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used to be necessary to counter-balance the fixed-weight frequency update
which has been recently changed for an adaptive rate (targeting stable starting frequency stats).
This commit is contained in:
Yann Collet
2021-09-08 07:56:43 -07:00
parent b096a5c626
commit 42a3ed752a
1 changed files with 0 additions and 24 deletions
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lib/compress/zstd_opt.c
-24
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@@ -14,7 +14,6 @@
#define ZSTD_LITFREQ_ADD 2 /* scaling factor for litFreq, so that frequencies adapt faster to new stats */
#define ZSTD_FREQ_DIV 4 /* log factor when using previous stats to init next stats */
#define ZSTD_MAX_PRICE (1<<30)
#define ZSTD_PREDEF_THRESHOLD 1024 /* if srcSize < ZSTD_PREDEF_THRESHOLD, symbols' cost is assumed static, directly determined by pre-defined distributions */
@@ -1253,28 +1252,7 @@ size_t ZSTD_compressBlock_btopt(
}
/* used in 2-pass strategy */
static U32 ZSTD_upscaleStat(unsigned* table, U32 lastEltIndex, int bonus)
{
U32 s, sum=0;
assert(ZSTD_FREQ_DIV+bonus >= 0);
for (s=0; s<lastEltIndex+1; s++) {
table[s] <<= ZSTD_FREQ_DIV+bonus;
table[s]--;
sum += table[s];
}
return sum;
}
/* used in 2-pass strategy */
MEM_STATIC void ZSTD_upscaleStats(optState_t* optPtr)
{
if (ZSTD_compressedLiterals(optPtr))
optPtr->litSum = ZSTD_upscaleStat(optPtr->litFreq, MaxLit, 0);
optPtr->litLengthSum = ZSTD_upscaleStat(optPtr->litLengthFreq, MaxLL, 0);
optPtr->matchLengthSum = ZSTD_upscaleStat(optPtr->matchLengthFreq, MaxML, 0);
optPtr->offCodeSum = ZSTD_upscaleStat(optPtr->offCodeFreq, MaxOff, 0);
}
/* ZSTD_initStats_ultra():
* make a first compression pass, just to seed stats with more accurate starting values.
@@ -1305,8 +1283,6 @@ ZSTD_initStats_ultra(ZSTD_matchState_t* ms,
ms->window.lowLimit = ms->window.dictLimit;
ms->nextToUpdate = ms->window.dictLimit;
/* re-inforce weight of collected statistics */
ZSTD_upscaleStats(&ms->opt);
}
size_t ZSTD_compressBlock_btultra(