From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
xdiff/xhistogram.c | 5 ++---
xdiff/xprepare.c | 24 ++++++++----------------
2 files changed, 10 insertions(+), 19 deletions(-)
diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c
index e694bfd9e31..6c1c88a69a1 100644
--- a/xdiff/xhistogram.c
+++ b/xdiff/xhistogram.c
@@ -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) \
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index abeb8fb84e6..7fae0727a02 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c
@@ -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;
}
--
gitgitgadget
