[PATCH v3 16/22] pickaxe -S: slightly optimize contains()
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Apr 12, 2021, 17:15 UTC
- Message-ID
- <patch-16.22-ed83c3add89-20210412T170457Z-avarab@gmail.com>
- In-Reply-To
- <cover-00.22-00000000000-20210412T170457Z-avarab@gmail.com>
When the "log -S<pat>" switch counts occurrences of <pat> on the pre-image and post-image of a change. As soon as we know we had e.g. 1 before and 2 now we can stop, we don't need to keep counting past 2.
With this change a diff between A and B may have different performance characteristics than between B and A. That's OK in this case, since we'll emit the same output, and the effect is to make one of them better.
I'm picking a check of "one" first on the assumption that it's a more common case to have files grow over time than not.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> --- diffcore-pickaxe.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c index 23362a23597..b7494fdf89c 100644 --- a/diffcore-pickaxe.c +++ b/diffcore-pickaxe.c @@ -68,7 +68,8 @@ static int diff_grep(mmfile_t *one, mmfile_t *two, return ecbdata.hit; } -static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws) +static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws, + unsigned int limit) { unsigned int cnt = 0; unsigned long sz = mf->size; @@ -88,6 +89,9 @@ static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws) sz--; } cnt++; + + if (limit && cnt == limit) + return cnt; } } else { /* Classic exact string match */ @@ -99,6 +103,9 @@ static unsigned int contains(mmfile_t *mf, regex_t *regexp, kwset_t kws) sz -= offset + kwsm.size[0]; data += offset + kwsm.size[0]; cnt++; + + if (limit && cnt == limit) + return cnt; } } return cnt; @@ -108,8 +115,8 @@ static int has_changes(mmfile_t *one, mmfile_t *two, struct diff_options *o, regex_t *regexp, kwset_t kws) { - unsigned int c1 = one ? contains(one, regexp, kws) : 0; - unsigned int c2 = two ? contains(two, regexp, kws) : 0; + unsigned int c1 = one ? contains(one, regexp, kws, 0) : 0; + unsigned int c2 = two ? contains(two, regexp, kws, c1 + 1) : 0; return c1 != c2; }
-- 2.31.1.639.g3d04783866f