[libzstd] Speed up single segment zstd_fast by 5%
This PR is based on top of PR #1563. The optimization is to process two input pointers per loop. It is based on ideas from [igzip] level 1, and talking to @gbtucker. | Platform | Silesia | Enwik8 | |-------------------------|-------------|--------| | OSX clang-10 | +5.3% | +5.4% | | i9 5 GHz gcc-8 | +6.6% | +6.6% | | i9 5 GHz clang-7 | +8.0% | +8.0% | | Skylake 2.4 GHz gcc-4.8 | +6.3% | +7.9% | | Skylake 2.4 GHz clang-7 | +6.2% | +7.5% | Testing on all Silesia files on my Intel i9-9900k with gcc-8 | Silesia File | Ratio Change | Speed Change | |--------------|--------------|--------------| | silesia.tar | +0.17% | +6.6% | | dickens | +0.25% | +7.0% | | mozilla | +0.02% | +6.8% | | mr | -0.30% | +10.9% | | nci | +1.28% | +4.5% | | ooffice | -0.35% | +10.7% | | osdb | +0.75% | +9.8% | | reymont | +0.65% | +4.6% | | samba | +0.70% | +5.9% | | sao | -0.01% | +14.0% | | webster | +0.30% | +5.5% | | xml | +0.92% | +5.3% | | x-ray | -0.00% | +1.4% | Same tests on Calgary. For brevity, I've only included files where compression ratio regressed or was much better. | Calgary File | Ratio Change | Speed Change | |--------------|--------------|--------------| | calgary.tar | +0.30% | +7.1% | | geo | -0.14% | +25.0% | | obj1 | -0.46% | +15.2% | | obj2 | -0.18% | +6.0% | | pic | +1.80% | +9.3% | | trans | -0.35% | +5.5% | We gain 0.1% of compression ratio on Silesia. We gain 0.3% of compression ratio on enwik8. I also tested on the GitHub and hg-commands datasets without a dictionary, and we gain a small amount of compression ratio on each, as well as speed. I tested the negative compression levels on Silesia on my Intel i9-9900k with gcc-8: | Level | Ratio Change | Speed Change | |-------|--------------|--------------| | -1 | +0.13% | +6.4% | | -2 | +4.6% | -1.5% | | -3 | +7.5% | -4.8% | | -4 | +8.5% | -6.9% | | -5 | +9.1% | -9.1% | Roughly, the negative levels now scale half as quickly. E.g. the new level 16 is roughly equivalent to the old level 8, but a bit quicker and smaller. If you don't think this is the right trade off, we can change it to multiply the step size by 2, instead of adding 1. I think this makes sense, because it gives a bit slower ratio decay. [igzip]: https://github.com/01org/isa-l/tree/master/igzipdev
Nick Terrell
Nick Terrell
parent
425ce5547c
commit
95624b77e4
|
|
@ -51,10 +51,12 @@ size_t ZSTD_compressBlock_fast_generic(
|
|||
U32* const hashTable = ms->hashTable;
|
||||
U32 const hlog = cParams->hashLog;
|
||||
/* support stepSize of 0 */
|
||||
U32 const stepSize = cParams->targetLength + !(cParams->targetLength);
|
||||
size_t const stepSize = cParams->targetLength + !(cParams->targetLength) + 1;
|
||||
const BYTE* const base = ms->window.base;
|
||||
const BYTE* const istart = (const BYTE*)src;
|
||||
const BYTE* ip = istart;
|
||||
/* We check ip0 (ip + 0) and ip1 (ip + 1) each loop */
|
||||
const BYTE* ip0 = istart;
|
||||
const BYTE* ip1;
|
||||
const BYTE* anchor = istart;
|
||||
const U32 prefixStartIndex = ms->window.dictLimit;
|
||||
const BYTE* const prefixStart = base + prefixStartIndex;
|
||||
|
|
@ -64,62 +66,96 @@ size_t ZSTD_compressBlock_fast_generic(
|
|||
U32 offsetSaved = 0;
|
||||
|
||||
/* init */
|
||||
ip += (ip == prefixStart);
|
||||
ip0 += (ip0 == prefixStart);
|
||||
ip1 = ip0 + 1;
|
||||
{
|
||||
U32 const maxRep = (U32)(ip - prefixStart);
|
||||
U32 const maxRep = (U32)(ip0 - prefixStart);
|
||||
if (offset_2 > maxRep) offsetSaved = offset_2, offset_2 = 0;
|
||||
if (offset_1 > maxRep) offsetSaved = offset_1, offset_1 = 0;
|
||||
}
|
||||
|
||||
/* Main Search Loop */
|
||||
while (ip < ilimit) { /* < instead of <=, because repcode check at (ip+1) */
|
||||
while (ip1 < ilimit) { /* < instead of <=, because check at ip0+2 */
|
||||
size_t mLength;
|
||||
size_t const h = ZSTD_hashPtr(ip, hlog, mls);
|
||||
U32 const current = (U32)(ip-base);
|
||||
U32 const matchIndex = hashTable[h];
|
||||
const BYTE* match = base + matchIndex;
|
||||
hashTable[h] = current; /* update hash table */
|
||||
BYTE const* ip2 = ip0 + 2;
|
||||
size_t const h0 = ZSTD_hashPtr(ip0, hlog, mls);
|
||||
U32 const val0 = MEM_read32(ip0);
|
||||
size_t const h1 = ZSTD_hashPtr(ip1, hlog, mls);
|
||||
U32 const val1 = MEM_read32(ip1);
|
||||
U32 const current0 = (U32)(ip0-base);
|
||||
U32 const current1 = (U32)(ip1-base);
|
||||
U32 const matchIndex0 = hashTable[h0];
|
||||
U32 const matchIndex1 = hashTable[h1];
|
||||
BYTE const* repMatch = ip2-offset_1;
|
||||
const BYTE* match0 = base + matchIndex0;
|
||||
const BYTE* match1 = base + matchIndex1;
|
||||
U32 offcode;
|
||||
hashTable[h0] = current0; /* update hash table */
|
||||
hashTable[h1] = current1; /* update hash table */
|
||||
|
||||
if ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1))) {
|
||||
mLength = ZSTD_count(ip+1+4, ip+1+4-offset_1, iend) + 4;
|
||||
ip++;
|
||||
ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);
|
||||
} else if ((matchIndex <= prefixStartIndex) || MEM_read32(match) != MEM_read32(ip)) {
|
||||
assert(stepSize >= 1);
|
||||
ip += ((ip-anchor) >> kSearchStrength) + stepSize;
|
||||
continue;
|
||||
} else {
|
||||
/* found a regular match */
|
||||
U32 const offset = (U32)(ip-match);
|
||||
mLength = ZSTD_count(ip+4, match+4, iend) + 4;
|
||||
while (((ip>anchor) & (match>prefixStart))
|
||||
&& (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
|
||||
offset_2 = offset_1;
|
||||
offset_1 = offset;
|
||||
ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
|
||||
assert(ip0 + 1 == ip1);
|
||||
|
||||
if ((offset_1 > 0) & (MEM_read32(repMatch) == MEM_read32(ip2))) {
|
||||
mLength = ip2[-1] == repMatch[-1] ? 1 : 0;
|
||||
ip0 = ip2 - mLength;
|
||||
match0 = repMatch - mLength;
|
||||
offcode = 0;
|
||||
goto _match;
|
||||
}
|
||||
if ((matchIndex0 > prefixStartIndex) && MEM_read32(match0) == val0) {
|
||||
/* found a regular match */
|
||||
goto _offset;
|
||||
}
|
||||
if ((matchIndex1 > prefixStartIndex) && MEM_read32(match1) == val1) {
|
||||
/* found a regular match after one literal */
|
||||
ip0 = ip1;
|
||||
match0 = match1;
|
||||
goto _offset;
|
||||
}
|
||||
{
|
||||
size_t const step = ((ip0-anchor) >> (kSearchStrength - 1)) + stepSize;
|
||||
assert(step >= 2);
|
||||
ip0 += step;
|
||||
ip1 += step;
|
||||
continue;
|
||||
}
|
||||
_offset: /* Requires: ip0, match0 */
|
||||
/* Compute the offset code */
|
||||
offset_2 = offset_1;
|
||||
offset_1 = (U32)(ip0-match0);
|
||||
offcode = offset_1 + ZSTD_REP_MOVE;
|
||||
mLength = 0;
|
||||
/* Count the backwards match length */
|
||||
while (((ip0>anchor) & (match0>prefixStart))
|
||||
&& (ip0[-1] == match0[-1])) { ip0--; match0--; mLength++; } /* catch up */
|
||||
|
||||
_match: /* Requires: ip0, match0, offcode */
|
||||
/* Count the forward length */
|
||||
mLength += ZSTD_count(ip0+mLength+4, match0+mLength+4, iend) + 4;
|
||||
ZSTD_storeSeq(seqStore, ip0-anchor, anchor, offcode, mLength-MINMATCH);
|
||||
/* match found */
|
||||
ip += mLength;
|
||||
anchor = ip;
|
||||
ip0 += mLength;
|
||||
anchor = ip0;
|
||||
ip1 = ip0 + 1;
|
||||
|
||||
if (ip <= ilimit) {
|
||||
if (ip0 <= ilimit) {
|
||||
/* Fill Table */
|
||||
assert(base+current+2 > istart); /* check base overflow */
|
||||
hashTable[ZSTD_hashPtr(base+current+2, hlog, mls)] = current+2; /* here because current+2 could be > iend-8 */
|
||||
hashTable[ZSTD_hashPtr(ip-2, hlog, mls)] = (U32)(ip-2-base);
|
||||
assert(base+current0+2 > istart); /* check base overflow */
|
||||
hashTable[ZSTD_hashPtr(base+current0+2, hlog, mls)] = current0+2; /* here because current+2 could be > iend-8 */
|
||||
hashTable[ZSTD_hashPtr(ip0-2, hlog, mls)] = (U32)(ip0-2-base);
|
||||
|
||||
while ( (ip <= ilimit)
|
||||
while ( (ip0 <= ilimit)
|
||||
&& ( (offset_2>0)
|
||||
& (MEM_read32(ip) == MEM_read32(ip - offset_2)) )) {
|
||||
& (MEM_read32(ip0) == MEM_read32(ip0 - offset_2)) )) {
|
||||
/* store sequence */
|
||||
size_t const rLength = ZSTD_count(ip+4, ip+4-offset_2, iend) + 4;
|
||||
size_t const rLength = ZSTD_count(ip0+4, ip0+4-offset_2, iend) + 4;
|
||||
U32 const tmpOff = offset_2; offset_2 = offset_1; offset_1 = tmpOff; /* swap offset_2 <=> offset_1 */
|
||||
hashTable[ZSTD_hashPtr(ip, hlog, mls)] = (U32)(ip-base);
|
||||
hashTable[ZSTD_hashPtr(ip0, hlog, mls)] = (U32)(ip0-base);
|
||||
ip0 += rLength;
|
||||
ip1 = ip0 + 1;
|
||||
ZSTD_storeSeq(seqStore, 0, anchor, 0, rLength-MINMATCH);
|
||||
ip += rLength;
|
||||
anchor = ip;
|
||||
continue; /* faster when present ... (?) */
|
||||
anchor = ip0;
|
||||
continue; /* faster when present (confirmed on gcc-8) ... (?) */
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue