From: Phillip Wood Date: Tue, 31 Mar 2026 09:44:15 GMT Subject: Re: [PATCH v4 4/6] xdiff/xdl_cleanup_records: make limits more clear Message-ID: <32c34d0d-9358-43e3-9d58-5999b3ffd6c2@gmail.com> In-Reply-To: <75fe3ea1250ab7dfa4e029f49f2ad353185afded.1774890003.git.gitgitgadget@gmail.com> Hi Ezekiel On 30/03/2026 18:00, Ezekiel Newren via GitGitGadget wrote: > From: Ezekiel Newren > > Make the handling of per-file limits and the minimal-case clearer. > * Use explicit per-file limit variables (mlim1, mlim2) and initialize > them. > * The additional condition `!need_min` is redudant now, remove it. > Best viewed with --color-words. > > Signed-off-by: Ezekiel Newren > --- > xdiff/xprepare.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c > index 386668a92d..bd8baf214d 100644 > --- a/xdiff/xprepare.c > +++ b/xdiff/xprepare.c > @@ -268,7 +268,7 @@ static bool xdl_clean_mmatch(uint8_t const *action, ptrdiff_t i, ptrdiff_t s, pt > * might be potentially discarded if they appear in a run of discardable. > */ > static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xdf2) { > - ptrdiff_t i, nm, mlim; > + ptrdiff_t i, nm, mlim1, mlim2; > xdlclass_t *rcrec; > uint8_t *action1 = NULL, *action2 = NULL; > bool need_min = !!(cf->flags & XDF_NEED_MINIMAL); > @@ -287,25 +287,30 @@ static int xdl_cleanup_records(xdlclassifier_t *cf, xdfile_t *xdf1, xdfile_t *xd > goto cleanup; > } > > + if (need_min) { > + /* i.e. infinity */ > + mlim1 = PTRDIFF_MAX; > + mlim2 = PTRDIFF_MAX; This is a nice improvement as it simplifies the checks below > + } else { > + mlim1 = XDL_MIN(xdl_bogosqrt(xdf1->nrec), XDL_MAX_EQLIMIT); > + mlim2 = XDL_MIN(xdl_bogosqrt(xdf2->nrec), XDL_MAX_EQLIMIT); As Junio has pointed out we now evaluate xdl_bogosqrt() twice which is unfortunate. It would have been nice to mention that in the commit message and explain why it does not matter. Personally I find the old code that set the limit just before each loop quite readable, the new version sets mlim2 a long way before it is used. Thanks Phillip > + } > + > /* > * Initialize temporary arrays with DISCARD, KEEP, or INVESTIGATE. > */ > - if ((mlim = (long)xdl_bogosqrt((uint64_t)xdf1->nrec)) > XDL_MAX_EQLIMIT) > - mlim = XDL_MAX_EQLIMIT; > for (i = xdf1->dstart; i <= xdf1->dend; i++) { > size_t mph1 = xdf1->recs[i].minimal_perfect_hash; > rcrec = cf->rcrecs[mph1]; > nm = rcrec ? rcrec->len2 : 0; > - action1[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP; > + action1[i] = (nm == 0) ? DISCARD: nm >= mlim1 ? INVESTIGATE: KEEP; > } > > - if ((mlim = (long)xdl_bogosqrt((uint64_t)xdf2->nrec)) > XDL_MAX_EQLIMIT) > - mlim = XDL_MAX_EQLIMIT; > for (i = xdf2->dstart; i <= xdf2->dend; i++) { > size_t mph2 = xdf2->recs[i].minimal_perfect_hash; > rcrec = cf->rcrecs[mph2]; > nm = rcrec ? rcrec->len1 : 0; > - action2[i] = (nm == 0) ? DISCARD: (nm >= mlim && !need_min) ? INVESTIGATE: KEEP; > + action2[i] = (nm == 0) ? DISCARD: nm >= mlim2 ? INVESTIGATE: KEEP; > } > > /*