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xdiff: don't waste time guessing the number of lines

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All lines must be read anyway, so classify them after they're read in.
Also move the memset() into xdl_init_classifier().

Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Ezekiel Newren 2026-01-02 18:52:17 +00:00 committed by Junio C Hamano
parent bcf8fd6345
commit db8a50ca6b
3 changed files with 22 additions and 53 deletions
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54
xdiff/xprepare.c
View File

@ -26,8 +26,6 @@
#define XDL_KPDIS_RUN 4
#define XDL_MAX_EQLIMIT 1024
#define XDL_SIMSCAN_WINDOW 100
#define XDL_GUESS_NLINES1 256
#define XDL_GUESS_NLINES2 20
#define DISCARD 0
#define KEEP 1
@ -55,6 +53,8 @@ typedef struct s_xdlclassifier {
static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
memset(cf, 0, sizeof(xdlclassifier_t));
cf->flags = flags;
cf->hbits = xdl_hashbits((unsigned int) size);
@ -134,12 +134,12 @@ static void xdl_free_ctx(xdfile_t *xdf)
}
static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
xdlclassifier_t *cf, xdfile_t *xdf) {
static int xdl_prepare_ctx(mmfile_t *mf, xdfile_t *xdf, uint64_t flags) {
long bsize;
uint64_t hav;
uint8_t const *blk, *cur, *top, *prev;
xrecord_t *crec;
long narec = 8;
xdf->reference_index = NULL;
xdf->changed = NULL;
@ -152,23 +152,21 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
if ((cur = blk = xdl_mmfile_first(mf, &bsize))) {
for (top = blk + bsize; cur < top; ) {
prev = cur;
hav = xdl_hash_record(&cur, top, xpp->flags);
hav = xdl_hash_record(&cur, top, flags);
if (XDL_ALLOC_GROW(xdf->recs, (long)xdf->nrec + 1, narec))
goto abort;
crec = &xdf->recs[xdf->nrec++];
crec->ptr = prev;
crec->size = cur - prev;
crec->line_hash = hav;
if (xdl_classify_record(pass, cf, crec) < 0)
goto abort;
}
}
if (!XDL_CALLOC_ARRAY(xdf->changed, xdf->nrec + 2))
goto abort;
if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
(XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)) {
if ((XDF_DIFF_ALG(flags) != XDF_PATIENCE_DIFF) &&
(XDF_DIFF_ALG(flags) != XDF_HISTOGRAM_DIFF)) {
if (!XDL_ALLOC_ARRAY(xdf->reference_index, xdf->nrec + 1))
goto abort;
}
@ -381,39 +379,31 @@ static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2
int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
xdfenv_t *xe) {
long enl1, enl2, sample;
xdlclassifier_t cf;
memset(&cf, 0, sizeof(cf));
if (xdl_prepare_ctx(mf1, &xe->xdf1, xpp->flags) < 0) {
/*
* For histogram diff, we can afford a smaller sample size and
* thus a poorer estimate of the number of lines, as the hash
* table (rhash) won't be filled up/grown. The number of lines
* (nrecs) will be updated correctly anyway by
* xdl_prepare_ctx().
*/
sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF
? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);
enl1 = xdl_guess_lines(mf1, sample) + 1;
enl2 = xdl_guess_lines(mf2, sample) + 1;
if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
return -1;
if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
xdl_free_classifier(&cf);
return -1;
}
if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
if (xdl_prepare_ctx(mf2, &xe->xdf2, xpp->flags) < 0) {
xdl_free_ctx(&xe->xdf1);
xdl_free_classifier(&cf);
return -1;
}
if (xdl_init_classifier(&cf, xe->xdf1.nrec + xe->xdf2.nrec + 1, xpp->flags) < 0)
return -1;
for (size_t i = 0; i < xe->xdf1.nrec; i++) {
xrecord_t *rec = &xe->xdf1.recs[i];
xdl_classify_record(1, &cf, rec);
}
for (size_t i = 0; i < xe->xdf2.nrec; i++) {
xrecord_t *rec = &xe->xdf2.recs[i];
xdl_classify_record(2, &cf, rec);
}
if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
(XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {

20
xdiff/xutils.c
View File

@ -118,26 +118,6 @@ void *xdl_cha_alloc(chastore_t *cha) {
return data;
}
long xdl_guess_lines(mmfile_t *mf, long sample) {
long nl = 0, size, tsize = 0;
char const *data, *cur, *top;
if ((cur = data = xdl_mmfile_first(mf, &size))) {
for (top = data + size; nl < sample && cur < top; ) {
nl++;
if (!(cur = memchr(cur, '\n', top - cur)))
cur = top;
else
cur++;
}
tsize += (long) (cur - data);
}
if (nl && tsize)
nl = xdl_mmfile_size(mf) / (tsize / nl);
return nl + 1;
}
int xdl_blankline(const char *line, long size, long flags)
{

1
xdiff/xutils.h
View File

@ -31,7 +31,6 @@ int xdl_emit_diffrec(char const *rec, long size, char const *pre, long psize,
int xdl_cha_init(chastore_t *cha, long isize, long icount);
void xdl_cha_free(chastore_t *cha);
void *xdl_cha_alloc(chastore_t *cha);
long xdl_guess_lines(mmfile_t *mf, long sample);
int xdl_blankline(const char *line, long size, long flags);
int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags);
uint64_t xdl_hash_record_verbatim(uint8_t const **data, uint8_t const *top);