AuroraMiddleware/lz4
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

implemented search accelerator

Browse Source 
greatly improves speed compared to non-accelerated,
especially for slower files.

On my laptop, -b12 :
```
calgary.tar :  4.3 MB/s =>  9.0 MB/s
enwik7      : 10.2 MB/s => 13.3 MB/s
silesia.tar :  4.0 MB/s =>  8.7 MB/s
```

Note : this is the simplified version,
without handling dictionaries, external buffer, nor pattern analyzer.
Current `dev` branch on these samples gives :
```
calgary.tar :  4.2 MB/s
enwik7      :  9.7 MB/s
silesia.tar :  3.5 MB/s
```

interestingly, it's slower,
presumably due to handling of dictionaries.
This commit is contained in:
Yann Collet 2018-05-03 16:31:41 -07:00
parent dc42707107
commit 434ace7244
1 changed files with 18 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
lib/lz4hc.c
View File

@ -1099,6 +1099,7 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4,
int nbAttempts = maxNbAttempts;
U32 const pattern = LZ4_read32(ip);
U32 matchIndex;
int fromMStart = 0;
DEBUGLOG(7, "LZ4HC_InsertAndGetWiderMatch");
/* First Match */
@ -1132,8 +1133,8 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4,
} /* while ((matchIndex>=lowestMatchIndex) && (nbAttempts)) */
assert(longest > MINMATCH);
while ((matchIndex>=lowestMatchIndex) && (nbAttempts)) {
const BYTE* const matchPtr = base + matchIndex;
while ((matchIndex-fromMStart>=lowestMatchIndex) && (nbAttempts)) {
const BYTE* const matchPtr = base + matchIndex - fromMStart;
assert(matchIndex < ipIndex);
assert(matchIndex >= dictLimit);
assert(matchPtr >= lowPrefixPtr);
@ -1146,6 +1147,21 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4,
if (mlt > longest) {
longest = mlt;
*matchpos = matchPtr;
matchIndex -= fromMStart; /* beginning of match */
if (1 && matchIndex + longest <= ipIndex) {
U32 distanceToNextMatch = 1;
int pos;
for (pos = 0; pos <= longest - MINMATCH; pos++) {
U32 const candidateDist = DELTANEXTU16(chainTable, matchIndex + pos);
if (candidateDist > distanceToNextMatch) {
distanceToNextMatch = candidateDist;
fromMStart = pos;
}
}
if (distanceToNextMatch > matchIndex) break; /* avoid overflow */
matchIndex -= distanceToNextMatch - fromMStart;
continue;
}
} } }
{ U32 const nextOffset = DELTANEXTU16(chainTable, matchIndex);