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introduced bit-fractional cost evaluation

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this improves compression ratio by a *tiny* amount.
It also reduces speed by a small amount.

Consequently, bit-fractional evaluation is only turned on for btultra.
This commit is contained in:
Yann Collet
2018-05-16 14:53:35 -07:00
parent 0b31304c8d
commit 18fc3d3cd5
2 changed files with 104 additions and 76 deletions
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lib/compress/zstd_compress_internal.h
+5 -7
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@@ -91,13 +91,11 @@ typedef struct {
U32 litLengthSum; /* nb of litLength codes */
U32 matchLengthSum; /* nb of matchLength codes */
U32 offCodeSum; /* nb of offset codes */
/* begin updated by ZSTD_setLog2Prices */
U32 log2litSum; /* pow2 to compare log2(litfreq) to */
U32 log2litLengthSum; /* pow2 to compare log2(llfreq) to */
U32 log2matchLengthSum; /* pow2 to compare log2(mlfreq) to */
U32 log2offCodeSum; /* pow2 to compare log2(offreq) to */
/* end : updated by ZSTD_setLog2Prices */
ZSTD_OptPrice_e priceType; /* prices can be determined dynamically, or follow dictionary statistics, or a pre-defined cost structure */
U32 litSumBasePrice; /* to compare to log2(litfreq) */
U32 litLengthSumBasePrice; /* to compare to log2(llfreq) */
U32 matchLengthSumBasePrice;/* to compare to log2(mlfreq) */
U32 offCodeSumBasePrice; /* to compare to log2(offreq) */
ZSTD_OptPrice_e priceType; /* prices can be determined dynamically, or follow a pre-defined cost structure */
const ZSTD_entropyCTables_t* symbolCosts; /* pre-calculated dictionary statistics */
} optState_t;