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speed optimized version of targetCBlockSize

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note that the size of individual compressed blocks will vary more wildly with this modification.
But it seems good enough for a first test, and fix the speed regression issue.
Further refinements can be attempted later.
This commit is contained in:
Yann Collet
2024-02-23 14:03:26 -08:00
parent 68a232c591
commit cc4530924b
2 changed files with 58 additions and 59 deletions
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lib/compress/zstd_compress_superblock.c
+54 -58
View File
@@ -122,7 +122,7 @@ ZSTD_compressSubBlock_literal(const HUF_CElt* hufTable,
}
*entropyWritten = 1;
DEBUGLOG(5, "Compressed literals: %u -> %u", (U32)litSize, (U32)(op-ostart));
return op-ostart;
return (size_t)(op-ostart);
}
static size_t
@@ -187,7 +187,7 @@ ZSTD_compressSubBlock_sequences(const ZSTD_fseCTables_t* fseTables,
else
op[0]=0xFF, MEM_writeLE16(op+1, (U16)(nbSeq - LONGNBSEQ)), op+=3;
if (nbSeq==0) {
return op - ostart;
return (size_t)(op - ostart);
}
/* seqHead : flags for FSE encoding type */
@@ -209,7 +209,7 @@ ZSTD_compressSubBlock_sequences(const ZSTD_fseCTables_t* fseTables,
}
{ size_t const bitstreamSize = ZSTD_encodeSequences(
op, oend - op,
op, (size_t)(oend - op),
fseTables->matchlengthCTable, mlCode,
fseTables->offcodeCTable, ofCode,
fseTables->litlengthCTable, llCode,
@@ -253,7 +253,7 @@ ZSTD_compressSubBlock_sequences(const ZSTD_fseCTables_t* fseTables,
#endif
*entropyWritten = 1;
return op - ostart;
return (size_t)(op - ostart);
}
/** ZSTD_compressSubBlock() :
@@ -296,11 +296,11 @@ static size_t ZSTD_compressSubBlock(const ZSTD_entropyCTables_t* entropy,
op += cSeqSize;
}
/* Write block header */
{ size_t cSize = (op-ostart)-ZSTD_blockHeaderSize;
{ size_t cSize = (size_t)(op-ostart) - ZSTD_blockHeaderSize;
U32 const cBlockHeader24 = lastBlock + (((U32)bt_compressed)<<1) + (U32)(cSize << 3);
MEM_writeLE24(ostart, cBlockHeader24);
}
return op-ostart;
return (size_t)(op-ostart);
}
static size_t ZSTD_estimateSubBlockSize_literal(const BYTE* literals, size_t litSize,
@@ -419,6 +419,16 @@ static int ZSTD_needSequenceEntropyTables(ZSTD_fseCTablesMetadata_t const* fseMe
return 0;
}
static size_t countLiterals(const seqDef* sp, size_t seqCount)
{
size_t n, total = 0;
assert(sp != NULL);
for (n=0; n<seqCount; n++) {
total += sp[n].litLength;
}
return total;
}
/** ZSTD_compressSubBlock_multi() :
* Breaks super-block into multiple sub-blocks and compresses them.
* Entropy will be written to the first block.
@@ -438,10 +448,12 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
{
const seqDef* const sstart = seqStorePtr->sequencesStart;
const seqDef* const send = seqStorePtr->sequences;
const seqDef* sp = sstart;
size_t const nbSeqs = (size_t)(send - sstart);
size_t nbSeqsPerBlock = nbSeqs;
const BYTE* const lstart = seqStorePtr->litStart;
const BYTE* const lend = seqStorePtr->lit;
const BYTE* lp = lstart;
size_t const nbLiterals = (size_t)(lend - lstart);
BYTE const* ip = (BYTE const*)src;
BYTE const* const iend = ip + srcSize;
BYTE* const ostart = (BYTE*)dst;
@@ -451,52 +463,50 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
const BYTE* mlCodePtr = seqStorePtr->mlCode;
const BYTE* ofCodePtr = seqStorePtr->ofCode;
size_t targetCBlockSize = cctxParams->targetCBlockSize;
size_t litSize, seqCount;
int writeLitEntropy = entropyMetadata->hufMetadata.hType == set_compressed;
int writeSeqEntropy = 1;
int lastSequence = 0;
size_t nbSubBlocks = 1;
DEBUGLOG(5, "ZSTD_compressSubBlock_multi (litSize=%u, nbSeq=%u)",
(unsigned)(lend-lp), (unsigned)(send-sstart));
litSize = 0;
seqCount = 0;
do {
size_t cBlockSizeEstimate = 0;
if (sstart == send) {
lastSequence = 1;
} else {
const seqDef* const sequence = sp + seqCount;
lastSequence = sequence == send - 1;
litSize += ZSTD_getSequenceLength(seqStorePtr, sequence).litLength;
seqCount++;
}
if (lastSequence) {
assert(lp <= lend);
assert(litSize <= (size_t)(lend - lp));
litSize = (size_t)(lend - lp);
}
/* I think there is an optimization opportunity here.
* Calling ZSTD_estimateSubBlockSize for every sequence can be wasteful
* since it recalculates estimate from scratch.
* For example, it would recount literal distribution and symbol codes every time.
*/
cBlockSizeEstimate = ZSTD_estimateSubBlockSize(lp, litSize, ofCodePtr, llCodePtr, mlCodePtr, seqCount,
&nextCBlock->entropy, entropyMetadata,
workspace, wkspSize, writeLitEntropy, writeSeqEntropy);
if (cBlockSizeEstimate > targetCBlockSize || lastSequence) {
/* let's start by a general estimation for the full block */
{ size_t const cBlockSizeEstimate =
ZSTD_estimateSubBlockSize(lp, nbLiterals,
ofCodePtr, llCodePtr, mlCodePtr, nbSeqs,
&nextCBlock->entropy, entropyMetadata,
workspace, wkspSize,
writeLitEntropy, writeSeqEntropy);
/* quick estimation */
nbSubBlocks = (cBlockSizeEstimate + (targetCBlockSize-1)) / targetCBlockSize;
assert(nbSubBlocks > 0);
nbSeqsPerBlock = nbSeqs / nbSubBlocks;
/* Note: this is very approximative. Obviously, some sub-blocks will be larger and others faster.
* But the contract of this feature has always been approximative, so for now we'll leverage it for speed.
* It can be refined later, for closer-to-target compressed block size, if it ever matters. */
}
/* write sub-blocks */
{ size_t n;
for (n=0; n < nbSubBlocks; n++) {
const seqDef* sp = sstart + n*nbSeqsPerBlock;
int lastSubBlock = (n==nbSubBlocks-1);
size_t const nbSeqsLastSubBlock = nbSeqs - (nbSubBlocks-1) * nbSeqsPerBlock;
size_t seqCount = lastSubBlock ? nbSeqsLastSubBlock : nbSeqsPerBlock;
size_t litSize = lastSubBlock ? (size_t)(lend-lp) : countLiterals(sp, seqCount);
int litEntropyWritten = 0;
int seqEntropyWritten = 0;
const size_t decompressedSize = ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, lastSequence);
const size_t decompressedSize =
ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, lastSubBlock);
const size_t cSize = ZSTD_compressSubBlock(&nextCBlock->entropy, entropyMetadata,
sp, seqCount,
lp, litSize,
llCodePtr, mlCodePtr, ofCodePtr,
cctxParams,
op, oend-op,
op, (size_t)(oend-op),
bmi2, writeLitEntropy, writeSeqEntropy,
&litEntropyWritten, &seqEntropyWritten,
lastBlock && lastSequence);
lastBlock && lastSubBlock);
FORWARD_IF_ERROR(cSize, "ZSTD_compressSubBlock failed");
if (cSize > 0 && cSize < decompressedSize) {
DEBUGLOG(5, "Committed the sub-block");
@@ -519,7 +529,8 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
}
}
}
} while (!lastSequence);
}
if (writeLitEntropy) {
DEBUGLOG(5, "ZSTD_compressSubBlock_multi has literal entropy tables unwritten");
ZSTD_memcpy(&nextCBlock->entropy.huf, &prevCBlock->entropy.huf, sizeof(prevCBlock->entropy.huf));
@@ -531,25 +542,10 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
DEBUGLOG(5, "ZSTD_compressSubBlock_multi has sequence entropy tables unwritten");
return 0;
}
if (ip < iend) {
size_t const cSize = ZSTD_noCompressBlock(op, oend - op, ip, iend - ip, lastBlock);
DEBUGLOG(5, "ZSTD_compressSubBlock_multi last sub-block uncompressed, %zu bytes", (size_t)(iend - ip));
FORWARD_IF_ERROR(cSize, "ZSTD_noCompressBlock failed");
assert(cSize != 0);
op += cSize;
/* We have to regenerate the repcodes because we've skipped some sequences */
if (sp < send) {
seqDef const* seq;
repcodes_t rep;
ZSTD_memcpy(&rep, prevCBlock->rep, sizeof(rep));
for (seq = sstart; seq < sp; ++seq) {
ZSTD_updateRep(rep.rep, seq->offBase, ZSTD_getSequenceLength(seqStorePtr, seq).litLength == 0);
}
ZSTD_memcpy(nextCBlock->rep, &rep, sizeof(rep));
}
}
DEBUGLOG(5, "ZSTD_compressSubBlock_multi compressed");
return op-ostart;
assert(ip == iend); (void)iend;
DEBUGLOG(5, "ZSTD_compressSubBlock_multi compressed: %u subBlocks, total compressed size = %u",
(unsigned)nbSubBlocks, (unsigned)(op-ostart));
return (size_t)(op-ostart);
}
size_t ZSTD_compressSuperBlock(ZSTD_CCtx* zc,