Skip to content

New algorithms for the long distance matcher #2483

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Feb 11, 2021
Merged

New algorithms for the long distance matcher #2483

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
9f327c0
new core ldm algorithm
mpu Jan 11, 2021
874a590
deal safely with short inputs in ZSTD_ldm_generateSequences
mpu Feb 4, 2021
e2ad174
fix some compiler warnings
mpu Feb 8, 2021
552efca
relocate large arrays from the stack to ldmState_t
mpu Feb 10, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 0 additions & 1 deletion lib/compress/zstd_compress.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1627,7 +1627,6 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
ZSTD_ldm_adjustParameters(&params.ldmParams, &params.cParams);
assert(params.ldmParams.hashLog >= params.ldmParams.bucketSizeLog);
assert(params.ldmParams.hashRateLog < 32);
zc->ldmState.hashPower = ZSTD_rollingHash_primePower(params.ldmParams.minMatchLength);
}

{ size_t const windowSize = MAX(1, (size_t)MIN(((U64)1 << params.cParams.windowLog), pledgedSrcSize));
Expand Down
13 changes: 11 additions & 2 deletions lib/compress/zstd_compress_internal.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -183,13 +183,22 @@ typedef struct {
U32 checksum;
} ldmEntry_t;

typedef struct {
BYTE const* split;
U32 hash;
U32 checksum;
ldmEntry_t* bucket;
} ldmMatchCandidate_t;

#define LDM_BATCH_SIZE 64

typedef struct {
ZSTD_window_t window; /* State for the window round buffer management */
ldmEntry_t* hashTable;
U32 loadedDictEnd;
BYTE* bucketOffsets; /* Next position in bucket to insert entry */
U64 hashPower; /* Used to compute the rolling hash.
* Depends on ldmParams.minMatchLength */
size_t splitIndices[LDM_BATCH_SIZE];
ldmMatchCandidate_t matchCandidates[LDM_BATCH_SIZE];
} ldmState_t;

typedef struct {
Expand Down
Loading