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Accepting request 437384 from home:Andreas_Schwab:Factory

Browse Source 
- gnulib-diffseq.patch, big-file-performance.patch: Avoid performance
  regression on big files (bsc#1004991)

OBS-URL: https://build.opensuse.org/request/show/437384
OBS-URL: https://build.opensuse.org/package/show/Base:System/diffutils?expand=0&rev=42
This commit is contained in:
Jiri Slaby 2016-10-28 09:01:36 +00:00 committed by Git OBS Bridge
parent 5c37307dbc
commit 9c171e3315
4 changed files with 304 additions and 0 deletions
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50
big-file-performance.patch Normal file
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@ -0,0 +1,50 @@
From 68b82f6f8419a815cfcf962b3061352d414dc606 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 25 Oct 2016 21:57:56 -0700
Subject: [PATCH] diff: fix big performance degradation in 3.4
* NEWS, doc/diffutils.texi (Overview): Document this.
* src/analyze.c (diff_2_files): Restore too_expensive heuristic,
but this time with a floor that is 16 times the old floor. This
should fix Bug#16848, by generating good-quality output for its
test case, while not introducing Bug#24715, by running nearly as
fast as diff-3.3 for that test case.
---
NEWS | 5 +++++
doc/diffutils.texi | 5 ++++-
src/analyze.c | 11 ++++++++++-
3 files changed, 19 insertions(+), 2 deletions(-)
Index: diffutils-3.5/src/analyze.c
===================================================================
--- diffutils-3.5.orig/src/analyze.c
+++ diffutils-3.5/src/analyze.c
@@ -534,6 +534,7 @@ diff_2_files (struct comparison *cmp)
{
struct context ctxt;
lin diags;
+ lin too_expensive;
/* Allocate vectors for the results of comparison:
a flag for each line of each file, saying whether that line
@@ -565,11 +566,19 @@ diff_2_files (struct comparison *cmp)
ctxt.heuristic = speed_large_files;
+ /* Set TOO_EXPENSIVE to be the approximate square root of the
+ input size, bounded below by 4096. 4096 seems to be good for
+ circa-2016 CPUs; see Bug#16848 and Bug#24715. */
+ too_expensive = 1;
+ for (; diags != 0; diags >>= 2)
+ too_expensive <<= 1;
+ ctxt.too_expensive = MAX (4096, too_expensive);
+
files[0] = cmp->file[0];
files[1] = cmp->file[1];
compareseq (0, cmp->file[0].nondiscarded_lines,
- 0, cmp->file[1].nondiscarded_lines, &ctxt);
+ 0, cmp->file[1].nondiscarded_lines, minimal, &ctxt);
free (ctxt.fdiag - (cmp->file[1].nondiscarded_lines + 1));

6
diffutils.changes
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@ -1,3 +1,9 @@
-------------------------------------------------------------------
Wed Oct 26 07:33:19 UTC 2016 - schwab@suse.de
- gnulib-diffseq.patch, big-file-performance.patch: Avoid performance
regression on big files (bsc#1004991)
-------------------------------------------------------------------
Mon Aug 22 20:34:19 UTC 2016 - astieger@suse.com

4
diffutils.spec
View File

@ -27,6 +27,8 @@ Source0: https://ftp.gnu.org/gnu/%{name}/%{name}-%{version}.tar.xz
Source1: https://ftp.gnu.org/gnu/%{name}/%{name}-%{version}.tar.xz.sig
# http://savannah.gnu.org/project/memberlist-gpgkeys.php?group=diffutils
Source2: %{name}.keyring
Patch1: gnulib-diffseq.patch
Patch2: big-file-performance.patch
BuildRequires: xz
Requires(pre): %{install_info_prereq}
Requires(preun): %{install_info_prereq}
@ -43,6 +45,8 @@ make source code patches, for instance.
%prep
%setup -q
%patch1 -p1
%patch2 -p1
%build
export CFLAGS="%{optflags} -fPIE"

244
gnulib-diffseq.patch Normal file
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@ -0,0 +1,244 @@
From d55ed0636eefeb43ad1aa8123416c33839652646 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 25 Oct 2016 14:59:29 -0700
Subject: [PATCH] diffseq: restore TOO_EXPENSIVE heuristic
* lib/diffseq.h: Problem with diffutils reported by Andreas Schwab
(Bug#24715). The simplest solution is to restore the
TOO_EXPENSIVE heuristic that I added to GNU diff in 1993, while
using a higher threshold to avoid Bug#16848 on smaller files.
* lib/diffseq.h (struct context): Restore member too_expensive.
(struct partition): Restore members lo_minimal, hi_minimal.
(diag, compareseq): Restore arg find_minimal. All uses changed.
(diag): Restore the TOO_EXPENSIVE heuristic that I added back in
1993 to make 'diff' run faster (but not as well) on large inputs,
but use a threshold of 4096 instead of the old 256.
* lib/fstrcmp.c (strcmp_bounded):
* lib/git-merge-changelog.c (compute_differences):
Adjust to diffseq.h changes.
---
ChangeLog | 17 +++++++
lib/diffseq.h | 118 ++++++++++++++++++++++++++++++++++++++++++----
lib/fstrcmp.c | 10 +++-
lib/git-merge-changelog.c | 3 +-
4 files changed, 137 insertions(+), 11 deletions(-)
Index: diffutils-3.5/lib/diffseq.h
===================================================================
--- diffutils-3.5.orig/lib/diffseq.h
+++ diffutils-3.5/lib/diffseq.h
@@ -34,7 +34,12 @@
The basic algorithm was independently discovered as described in:
"Algorithms for Approximate String Matching", Esko Ukkonen,
Information and Control Vol. 64, 1985, pp. 100-118,
- <http://dx.doi.org/10.1016/S0019-9958(85)80046-2>. */
+ <http://dx.doi.org/10.1016/S0019-9958(85)80046-2>.
+
+ Unless the 'find_minimal' flag is set, this code uses the TOO_EXPENSIVE
+ heuristic, by Paul Eggert, to limit the cost to O(N**1.5 log N)
+ at the price of producing suboptimal output for large inputs with
+ many differences. */
/* Before including this file, you need to define:
ELEMENT The element type of the vectors being compared.
@@ -123,6 +128,9 @@ struct context
bool heuristic;
#endif
+ /* Edit scripts longer than this are too expensive to compute. */
+ OFFSET too_expensive;
+
/* Snakes bigger than this are considered "big". */
#define SNAKE_LIMIT 20
};
@@ -132,6 +140,12 @@ struct partition
/* Midpoints of this partition. */
OFFSET xmid;
OFFSET ymid;
+
+ /* True if low half will be analyzed minimally. */
+ bool lo_minimal;
+
+ /* Likewise for high half. */
+ bool hi_minimal;
};
@@ -143,10 +157,17 @@ struct partition
When the two searches meet, we have found the midpoint of the shortest
edit sequence.
- Set *PART to the midpoint (XMID,YMID). The diagonal number
+ If FIND_MINIMAL is true, find the minimal edit script regardless of
+ expense. Otherwise, if the search is too expensive, use heuristics to
+ stop the search and report a suboptimal answer.
+
+ Set PART->(xmid,ymid) to the midpoint (XMID,YMID). The diagonal number
XMID - YMID equals the number of inserted elements minus the number
of deleted elements (counting only elements before the midpoint).
+ Set PART->lo_minimal to true iff the minimal edit script for the
+ left half of the partition is known; similarly for PART->hi_minimal.
+
This function assumes that the first elements of the specified portions
of the two vectors do not match, and likewise that the last elements do not
match. The caller must trim matching elements from the beginning and end
@@ -156,7 +177,7 @@ struct partition
suboptimal diff output. It cannot cause incorrect diff output. */
static void
-diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
+diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim, bool find_minimal,
struct partition *part, struct context *ctxt)
{
OFFSET *const fd = ctxt->fdiag; /* Give the compiler a chance. */
@@ -216,6 +237,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
{
part->xmid = x;
part->ymid = y;
+ part->lo_minimal = part->hi_minimal = true;
return;
}
}
@@ -248,10 +270,14 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
{
part->xmid = x;
part->ymid = y;
+ part->lo_minimal = part->hi_minimal = true;
return;
}
}
+ if (find_minimal)
+ continue;
+
#ifdef USE_HEURISTIC
/* Heuristic: check occasionally for a diagonal that has made lots
of progress compared with the edit distance. If we have any
@@ -295,7 +321,11 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
}
}
if (best > 0)
- return;
+ {
+ part->lo_minimal = true;
+ part->hi_minimal = false;
+ return;
+ }
}
{
@@ -330,10 +360,77 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
}
}
if (best > 0)
- return;
+ {
+ part->lo_minimal = false;
+ part->hi_minimal = true;
+ return;
+ }
}
}
#endif /* USE_HEURISTIC */
+
+ /* Heuristic: if we've gone well beyond the call of duty, give up
+ and report halfway between our best results so far. */
+ if (c >= ctxt->too_expensive)
+ {
+ OFFSET fxybest;
+ OFFSET fxbest IF_LINT (= 0);
+ OFFSET bxybest;
+ OFFSET bxbest IF_LINT (= 0);
+
+ /* Find forward diagonal that maximizes X + Y. */
+ fxybest = -1;
+ for (d = fmax; d >= fmin; d -= 2)
+ {
+ OFFSET x = MIN (fd[d], xlim);
+ OFFSET y = x - d;
+ if (ylim < y)
+ {
+ x = ylim + d;
+ y = ylim;
+ }
+ if (fxybest < x + y)
+ {
+ fxybest = x + y;
+ fxbest = x;
+ }
+ }
+
+ /* Find backward diagonal that minimizes X + Y. */
+ bxybest = OFFSET_MAX;
+ for (d = bmax; d >= bmin; d -= 2)
+ {
+ OFFSET x = MAX (xoff, bd[d]);
+ OFFSET y = x - d;
+ if (y < yoff)
+ {
+ x = yoff + d;
+ y = yoff;
+ }
+ if (x + y < bxybest)
+ {
+ bxybest = x + y;
+ bxbest = x;
+ }
+ }
+
+ /* Use the better of the two diagonals. */
+ if ((xlim + ylim) - bxybest < fxybest - (xoff + yoff))
+ {
+ part->xmid = fxbest;
+ part->ymid = fxybest - fxbest;
+ part->lo_minimal = true;
+ part->hi_minimal = false;
+ }
+ else
+ {
+ part->xmid = bxbest;
+ part->ymid = bxybest - bxbest;
+ part->lo_minimal = false;
+ part->hi_minimal = true;
+ }
+ return;
+ }
}
#undef XREF_YREF_EQUAL
}
@@ -347,6 +444,9 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
Note that XLIM, YLIM are exclusive bounds. All indices into the vectors
are origin-0.
+ If FIND_MINIMAL, find a minimal difference no matter how
+ expensive it is.
+
The results are recorded by invoking NOTE_DELETE and NOTE_INSERT.
Return false if terminated normally, or true if terminated through early
@@ -354,7 +454,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET y
static bool
compareseq (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
- struct context *ctxt)
+ bool find_minimal, struct context *ctxt)
{
#ifdef ELEMENT
ELEMENT const *xv = ctxt->xvec; /* Help the compiler. */
@@ -400,12 +500,12 @@ compareseq (OFFSET xoff, OFFSET xlim, OF
struct partition part IF_LINT2 (= { .xmid = 0, .ymid = 0 });
/* Find a point of correspondence in the middle of the vectors. */
- diag (xoff, xlim, yoff, ylim, &part, ctxt);
+ diag (xoff, xlim, yoff, ylim, find_minimal, &part, ctxt);
/* Use the partitions to split this problem into subproblems. */
- if (compareseq (xoff, part.xmid, yoff, part.ymid, ctxt))
+ if (compareseq (xoff, part.xmid, yoff, part.ymid, part.lo_minimal, ctxt))
return true;
- if (compareseq (part.xmid, xlim, part.ymid, ylim, ctxt))
+ if (compareseq (part.xmid, xlim, part.ymid, ylim, part.hi_minimal, ctxt))
return true;
}