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Fix small literals cost estimate issue in optimizer, gain a small amount of compression and reduction of token count

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emmanuel-marty 2019-04-11 23:47:57 +02:00
parent 4c5d44fff4
commit cf51f1775a
1 changed files with 31 additions and 8 deletions
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39
src/shrink.c
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@ -502,6 +502,8 @@ static void lzsa_optimize_matches(lsza_compressor *pCompressor, const int nStart
int nLiteralsLen = nLastLiteralsOffset - i;
nBestCost = 1 + cost[i + 1] + lzsa_get_literals_varlen_size(nLiteralsLen);
if (nLiteralsLen > 1)
nBestCost -= lzsa_get_literals_varlen_size(nLiteralsLen - 1);
nBestMatchLen = 0;
nBestMatchOffset = 0;
@ -518,9 +520,13 @@ static void lzsa_optimize_matches(lsza_compressor *pCompressor, const int nStart
if (nRemainingLiteralsLen < 0) nRemainingLiteralsLen = 0;
if ((i + nMatchLen) > (nEndOffset - LAST_LITERALS))
nMatchLen = nEndOffset - LAST_LITERALS - i;
nCurCost = 1 + lzsa_get_literals_varlen_size(nRemainingLiteralsLen) + nMatchOffsetSize + lzsa_get_match_varlen_size(nMatchLen - MIN_MATCH_SIZE);
if ((i + nMatchLen) < nEndOffset)
nCurCost += cost[i + nMatchLen];
nCurCost += cost[i + nMatchLen];
if (nRemainingLiteralsLen > 1)
nCurCost -= lzsa_get_literals_varlen_size(nRemainingLiteralsLen - 1);
if (nBestCost >= nCurCost) {
nBestCost = nCurCost;
@ -530,9 +536,13 @@ static void lzsa_optimize_matches(lsza_compressor *pCompressor, const int nStart
}
else {
if (pMatch[m].length >= MIN_MATCH_SIZE) {
int nMatchLen = pMatch[m].length;
int k, nMatchRunLen;
nMatchRunLen = pMatch[m].length;
if ((i + nMatchLen) > (nEndOffset - LAST_LITERALS))
nMatchLen = nEndOffset - LAST_LITERALS - i;
nMatchRunLen = nMatchLen;
if (nMatchRunLen > MATCH_RUN_LEN)
nMatchRunLen = MATCH_RUN_LEN;
@ -543,8 +553,9 @@ static void lzsa_optimize_matches(lsza_compressor *pCompressor, const int nStart
if (nRemainingLiteralsLen < 0) nRemainingLiteralsLen = 0;
nCurCost = 1 + lzsa_get_literals_varlen_size(nRemainingLiteralsLen) + nMatchOffsetSize /* no extra match len bytes */;
if ((i + k) < nEndOffset)
nCurCost += cost[i + k];
nCurCost += cost[i + k];
if (nRemainingLiteralsLen > 1)
nCurCost -= lzsa_get_literals_varlen_size(nRemainingLiteralsLen - 1);
if (nBestCost >= nCurCost) {
nBestCost = nCurCost;
@ -553,15 +564,16 @@ static void lzsa_optimize_matches(lsza_compressor *pCompressor, const int nStart
}
}
for (; k <= pMatch[m].length; k++) {
for (; k <= nMatchLen; k++) {
int nCurCost;
int nRemainingLiteralsLen = nLastLiteralsOffset - (i + k);
if (nRemainingLiteralsLen < 0) nRemainingLiteralsLen = 0;
nCurCost = 1 + lzsa_get_literals_varlen_size(nRemainingLiteralsLen) + nMatchOffsetSize + lzsa_get_match_varlen_size(k - MIN_MATCH_SIZE);
if ((i + k) < nEndOffset)
nCurCost += cost[i + k];
nCurCost += cost[i + k];
if (nRemainingLiteralsLen > 1)
nCurCost -= lzsa_get_literals_varlen_size(nRemainingLiteralsLen - 1);
if (nBestCost >= nCurCost) {
nBestCost = nCurCost;
@ -642,6 +654,17 @@ static void lzsa_optimize_command_count(lsza_compressor *pCompressor, const int
i += nMatchLen;
}
else {
if ((i + nMatchLen) < nEndOffset && nMatchLen >= LCP_MAX && pMatch->offset == 1 &&
pCompressor->match[(i + nMatchLen) << MATCHES_PER_OFFSET_SHIFT].offset == 1 &&
(nMatchLen + pCompressor->match[(i + nMatchLen) << MATCHES_PER_OFFSET_SHIFT].length) <= 65535) {
/* Join */
pMatch->length += pCompressor->match[(i + nMatchLen) << MATCHES_PER_OFFSET_SHIFT].length;
pCompressor->match[(i + nMatchLen) << MATCHES_PER_OFFSET_SHIFT].offset = 0;
pCompressor->match[(i + nMatchLen) << MATCHES_PER_OFFSET_SHIFT].length = -1;
continue;
}
nNumLiterals = 0;
i += nMatchLen;
}