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diff histogram: intern strings 

Histogram is the only diff algorithm not to call
xdl_classify_record(). xdl_classify_record() ensures that the hash
values of two strings that are not equal differ which means that it is
not necessary to use xdl_recmatch() when comparing lines, all that is
necessary is to compare the hash values. This gives a 7% reduction in
the runtime of "git log --patch" when using the histogram diff
algorithm.

Test                                  HEAD^             HEAD
-----------------------------------------------------------------------------
4000.1: log -3000 (baseline)          0.18(0.14+0.04)   0.19(0.17+0.02) +5.6%
4000.2: log --raw -3000 (tree-only)   0.99(0.77+0.21)   0.98(0.78+0.20) -1.0%
4000.3: log -p -3000 (Myers)          4.84(4.31+0.51)   4.81(4.15+0.64) -0.6%
4000.4: log -p -3000 --histogram      6.34(5.86+0.46)   5.87(5.19+0.66) -7.4%
4000.5: log -p -3000 --patience       5.39(4.60+0.76)   5.35(4.60+0.73) -0.7%

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Phillip Wood 2021-11-17 11:20:23 +00:00 committed by Junio C Hamano
parent cd3e606211
commit 663c5ad035
2 changed files with 10 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
xdiff/xhistogram.c
View File

@ -91,9 +91,8 @@ struct region {
static int cmp_recs(xpparam_t const *xpp,
xrecord_t *r1, xrecord_t *r2)
{
return r1->ha == r2->ha &&
xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
xpp->flags);
return r1->ha == r2->ha;
}
#define CMP_ENV(xpp, env, s1, l1, s2, l2) \

24
xdiff/xprepare.c
View File

@ -181,15 +181,11 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))
goto abort;
if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
hbits = hsize = 0;
else {
hbits = xdl_hashbits((unsigned int) narec);
hsize = 1 << hbits;
if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
goto abort;
memset(rhash, 0, hsize * sizeof(xrecord_t *));
}
hbits = xdl_hashbits((unsigned int) narec);
hsize = 1 << hbits;
if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
goto abort;
memset(rhash, 0, hsize * sizeof(xrecord_t *));
nrec = 0;
if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
@ -208,9 +204,7 @@ static int xdl_prepare_ctx(unsigned int pass, mmfile_t *mf, long narec, xpparam_
crec->size = (long) (cur - prev);
crec->ha = hav;
recs[nrec++] = crec;
if ((XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
if (xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
goto abort;
}
}
@ -279,8 +273,7 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
enl1 = xdl_guess_lines(mf1, sample) + 1;
enl2 = xdl_guess_lines(mf2, sample) + 1;
if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF &&
xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
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) {
@ -305,8 +298,7 @@ int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
return -1;
}
if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)
xdl_free_classifier(&cf);
xdl_free_classifier(&cf);
return 0;
}