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Merge pull request #2983 from facebook/minLitPricev2

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[opt] minor compression ratio improvement
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Yann Collet authored and GitHub committed 2022-01-20 16:02:31 -08:00
2 parents 330c97d2bf 5595aec629
commit 71921e596f
2 files changed
+16 -13
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lib/compress/zstd_opt.c
+6 -3
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@@ -255,11 +255,14 @@ static U32 ZSTD_rawLiteralsCost(const BYTE* const literals, U32 const litLength,
return (litLength*6) * BITCOST_MULTIPLIER; /* 6 bit per literal - no statistic used */
/* dynamic statistics */
{ U32 price = litLength * optPtr->litSumBasePrice;
{ U32 price = optPtr->litSumBasePrice * litLength;
U32 const litPriceMax = optPtr->litSumBasePrice - BITCOST_MULTIPLIER;
U32 u;
assert(optPtr->litSumBasePrice >= BITCOST_MULTIPLIER);
for (u=0; u < litLength; u++) {
assert(WEIGHT(optPtr->litFreq[literals[u]], optLevel) <= optPtr->litSumBasePrice); /* literal cost should never be negative */
price -= WEIGHT(optPtr->litFreq[literals[u]], optLevel);
U32 litPrice = WEIGHT(optPtr->litFreq[literals[u]], optLevel);
if (UNLIKELY(litPrice > litPriceMax)) litPrice = litPriceMax;
price -= litPrice;
}
return price;
}