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xdiff/xprepare: improve O(n*m) performance in xdl_cleanup_records()
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In xdl_cleanup_records(), we see O(n*m) performance, where n is the
number of records from xdf->dstart to xdf->dend, and m is the size of a
bucket in xdf->rhash (<= by mlim).

Here, we improve this to O(n) by pre-computing nm (in rcrec->len(1|2))
in xdl_classify_record().

Reported-by: Marat Radchenko <marat@slonopotamus.org>
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Tay Ray Chuan authored and Junio C Hamano committed Aug 18, 2011
1 parent 4bfe7cb commit 27af01d
Showing 1 changed file with 50 additions and 36 deletions.
86 changes: 50 additions & 36 deletions xdiff/xprepare.c
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Original file line number Diff line number Diff line change
Expand Up @@ -34,13 +34,16 @@ typedef struct s_xdlclass {
char const *line;
long size;
long idx;
long len1, len2;
} xdlclass_t;

typedef struct s_xdlclassifier {
unsigned int hbits;
long hsize;
xdlclass_t **rchash;
chastore_t ncha;
xdlclass_t **rcrecs;
long alloc;
long count;
long flags;
} xdlclassifier_t;
Expand All @@ -50,15 +53,15 @@ typedef struct s_xdlclassifier {

static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);
static void xdl_free_classifier(xdlclassifier_t *cf);
static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
xrecord_t *rec);
static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
unsigned int hbits, xrecord_t *rec);
static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
xdlclassifier_t *cf, xdfile_t *xdf);
static void xdl_free_ctx(xdfile_t *xdf);
static int xdl_clean_mmatch(char const *dis, long i, long s, long e);
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2);



Expand All @@ -83,6 +86,14 @@ static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
for (i = 0; i < cf->hsize; i++)
cf->rchash[i] = NULL;

cf->alloc = size;
if (!(cf->rcrecs = (xdlclass_t **) xdl_malloc(cf->alloc * sizeof(xdlclass_t *)))) {

xdl_free(cf->rchash);
xdl_cha_free(&cf->ncha);
return -1;
}

cf->count = 0;

return 0;
Expand All @@ -91,16 +102,18 @@ static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {

static void xdl_free_classifier(xdlclassifier_t *cf) {

xdl_free(cf->rcrecs);
xdl_free(cf->rchash);
xdl_cha_free(&cf->ncha);
}


static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
xrecord_t *rec) {
static int xdl_classify_record(unsigned int pass, xdlclassifier_t *cf, xrecord_t **rhash,
unsigned int hbits, xrecord_t *rec) {
long hi;
char const *line;
xdlclass_t *rcrec;
xdlclass_t **rcrecs;

line = rec->ptr;
hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
Expand All @@ -116,13 +129,25 @@ static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned
return -1;
}
rcrec->idx = cf->count++;
if (cf->count > cf->alloc) {
cf->alloc *= 2;
if (!(rcrecs = (xdlclass_t **) xdl_realloc(cf->rcrecs, cf->alloc * sizeof(xdlclass_t *)))) {

return -1;
}
cf->rcrecs = rcrecs;
}
cf->rcrecs[rcrec->idx] = rcrec;
rcrec->line = line;
rcrec->size = rec->size;
rcrec->ha = rec->ha;
rcrec->len1 = rcrec->len2 = 0;
rcrec->next = cf->rchash[hi];
cf->rchash[hi] = rcrec;
}

(pass == 1) ? rcrec->len1++ : rcrec->len2++;

rec->ha = (unsigned long) rcrec->idx;

hi = (long) XDL_HASHLONG(rec->ha, hbits);
Expand All @@ -133,7 +158,7 @@ static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned
}


static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_t const *xpp,
xdlclassifier_t *cf, xdfile_t *xdf) {
unsigned int hbits;
long i, nrec, hsize, bsize;
Expand Down Expand Up @@ -200,7 +225,7 @@ static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
crec->ha = hav;
recs[nrec++] = crec;

if (xdl_classify_record(cf, rhash, hbits, crec) < 0) {
if (xdl_classify_record(pass, cf, rhash, hbits, crec) < 0) {

xdl_free(rhash);
xdl_free(recs);
Expand Down Expand Up @@ -276,28 +301,28 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
return -1;
}

if (xdl_prepare_ctx(mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {

xdl_free_classifier(&cf);
return -1;
}
if (xdl_prepare_ctx(mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
if (xdl_prepare_ctx(2, mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {

xdl_free_ctx(&xe->xdf1);
xdl_free_classifier(&cf);
return -1;
}

xdl_free_classifier(&cf);

if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
xdl_optimize_ctxs(&xe->xdf1, &xe->xdf2) < 0) {
xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {

xdl_free_ctx(&xe->xdf2);
xdl_free_ctx(&xe->xdf1);
return -1;
}

xdl_free_classifier(&cf);

return 0;
}

Expand Down Expand Up @@ -372,11 +397,10 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
* matches on the other file. Also, lines that have multiple matches
* might be potentially discarded if they happear in a run of discardable.
*/
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2) {
long i, nm, rhi, nreff, mlim;
unsigned long hav;
static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {
long i, nm, nreff;
xrecord_t **recs;
xrecord_t *rec;
xdlclass_t *rcrec;
char *dis, *dis1, *dis2;

if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {
Expand All @@ -387,26 +411,16 @@ static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2) {
dis1 = dis;
dis2 = dis1 + xdf1->nrec + 1;

if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
mlim = XDL_MAX_EQLIMIT;
for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
hav = (*recs)->ha;
rhi = (long) XDL_HASHLONG(hav, xdf2->hbits);
for (nm = 0, rec = xdf2->rhash[rhi]; rec; rec = rec->next)
if (rec->ha == hav && ++nm == mlim)
break;
dis1[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
rcrec = cf->rcrecs[(*recs)->ha];
nm = rcrec ? rcrec->len2 : 0;
dis1[i] = (nm == 0) ? 0: 1;
}

if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
mlim = XDL_MAX_EQLIMIT;
for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
hav = (*recs)->ha;
rhi = (long) XDL_HASHLONG(hav, xdf1->hbits);
for (nm = 0, rec = xdf1->rhash[rhi]; rec; rec = rec->next)
if (rec->ha == hav && ++nm == mlim)
break;
dis2[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
rcrec = cf->rcrecs[(*recs)->ha];
nm = rcrec ? rcrec->len1 : 0;
dis2[i] = (nm == 0) ? 0: 1;
}

for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
Expand Down Expand Up @@ -468,10 +482,10 @@ static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
}


static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2) {
static int xdl_optimize_ctxs(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) {

if (xdl_trim_ends(xdf1, xdf2) < 0 ||
xdl_cleanup_records(xdf1, xdf2) < 0) {
xdl_cleanup_records(cf, xdf1, xdf2) < 0) {

return -1;
}
Expand Down

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