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Load more dictionary positions into table if empty 

If the hash table is empty load positions into the hash table
that we would otherwise skip.

| Level | Data Set     | Improvement |
|-------|--------------|-------------|
| 1     | github       | 0.44%       |
| 1     | hg-changelog | 0.13%       |
| 1     | hg-commands  | 1.28%       |
| 1     | hg-manifest  | 0.70%       |
| 3     | github       | 0.74%       |
| 3     | hg-changelog | 0.87%       |
| 3     | hg-commands  | 1.74%       |
| 3     | hg-manifest  | 0.23%       |
dev
Nick Terrell 2018-01-12 12:26:47 -08:00
parent 04c00f9388
commit 9a211d1f05
2 changed files with 28 additions and 9 deletions
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21
lib/compress/zstd_double_fast.c
View File

@ -21,12 +21,23 @@ void ZSTD_fillDoubleHashTable(ZSTD_CCtx* cctx, const void* end, const U32 mls)
const BYTE* const base = cctx->base; const BYTE* const base = cctx->base;
const BYTE* ip = base + cctx->nextToUpdate; const BYTE* ip = base + cctx->nextToUpdate;
const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE; const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE;
const size_t fastHashFillStep = 3; const U32 fastHashFillStep = 3;
while(ip <= iend) { /* Always insert every fastHashFillStep position into the hash tables.
hashSmall[ZSTD_hashPtr(ip, hBitsS, mls)] = (U32)(ip - base); * Insert the other positions into the large hash table if their entry
hashLarge[ZSTD_hashPtr(ip, hBitsL, 8)] = (U32)(ip - base); * is empty.
ip += fastHashFillStep; */
for (; ip + fastHashFillStep - 1 <= iend; ip += fastHashFillStep) {
U32 const current = (U32)(ip - base);
U32 i;
for (i = 0; i < fastHashFillStep; ++i) {
size_t const smHash = ZSTD_hashPtr(ip + i, hBitsS, mls);
size_t const lgHash = ZSTD_hashPtr(ip + i, hBitsL, 8);
if (i == 0)
hashSmall[smHash] = current + i;
if (i == 0 || hashLarge[lgHash] == 0)
hashLarge[lgHash] = current + i;
}
} }
} }

16
lib/compress/zstd_fast.c
View File

@ -19,11 +19,19 @@ void ZSTD_fillHashTable (ZSTD_CCtx* zc, const void* end, const U32 mls)
const BYTE* const base = zc->base; const BYTE* const base = zc->base;
const BYTE* ip = base + zc->nextToUpdate; const BYTE* ip = base + zc->nextToUpdate;
const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE; const BYTE* const iend = ((const BYTE*)end) - HASH_READ_SIZE;
const size_t fastHashFillStep = 3; const U32 fastHashFillStep = 3;
while(ip <= iend) { /* Always insert every fastHashFillStep position into the hash table.
hashTable[ZSTD_hashPtr(ip, hBits, mls)] = (U32)(ip - base); * Insert the other positions if their hash entry is empty.
ip += fastHashFillStep; */
for (; ip + fastHashFillStep - 1 <= iend; ip += fastHashFillStep) {
U32 const current = (U32)(ip - base);
U32 i;
for (i = 0; i < fastHashFillStep; ++i) {
size_t const hash = ZSTD_hashPtr(ip + i, hBits, mls);
if (i == 0 || hashTable[hash] == 0)
hashTable[hash] = current + i;
}
} }
} }