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| author |  Tay Ray Chuan <rctay89@gmail.com> | 2011-07-12 14:10:27 +0800 |
|---|---|---|
| committer |  Junio C Hamano <gitster@pobox.com> | 2011-07-12 09:30:00 -0700 |
| commit | 86abba801575892a8a2b161aa29518c1ed05e1f1 (patch) | |
| tree | e2a5a2264646e2bbde43dfd8bff10369daec7c5b /xdiff/xprepare.c | |
| parent | xdiff/xprepare: skip classification (diff) | |
| download | tgif-86abba801575892a8a2b161aa29518c1ed05e1f1.tar.xz | |
xdiff/xprepare: use a smaller sample size for histogram diff
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. This is safe as the final count of lines (xdf.nrecs)
will be updated correctly anyway by xdl_prepare_ctx().
This gives us a small boost in performance.
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'xdiff/xprepare.c')
| -rw-r--r-- | xdiff/xprepare.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c index 7556538df5..dfbb0de987 100644 --- a/xdiff/xprepare.c +++ b/xdiff/xprepare.c @@ -26,6 +26,8 @@ #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 typedef struct s_xdlclass { @@ -239,11 +241,20 @@ static void xdl_free_ctx(xdfile_t *xdf) { int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdfenv_t *xe) { - long enl1, enl2; + long enl1, enl2, sample; xdlclassifier_t cf; - enl1 = xdl_guess_lines(mf1) + 1; - enl2 = xdl_guess_lines(mf2) + 1; + /* + * 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 = 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 (!(xpp->flags & XDF_HISTOGRAM_DIFF) && xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) { |