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When the myers algorithm is selected the input files are pre-processed
to remove any common prefix and suffix and any lines that appear
in only one file. This requires a map to be created between the
lines that are processed by the myers algorithm and the lines in
the original file. That map does not include the common lines at the
beginning and end of the files but the array is allocated to be the
size of the whole file. Move the allocation into xdl_cleanup_records()
where the map is populated and we know how big it needs to be.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If either of the two allocations fail we want to take the same action
so use a single if statement. This saves a few lines and makes it
easier for the next commit to add a couple more allocations.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Remove the "s" parameter as, since the last commit, this function
is always called with s == 0. Also change parameter "e" to expect a
length, rather than the index of the last line to simplify the caller.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When the myers algorithm is selected the input files are pre-processed
to remove any common prefix and suffix. Then any lines that appear
only in one side of the diff are marked as changed and frequently
occurring lines are marked as changed if they are adjacent to a
changed line. This step requires a couple of temporary arrays. As as
the common prefix and suffix have already been removed, the arrays
only need to be big enough to hold the lines between them, not the
whole file. Reduce the size of the arrays and adjust the loops that
use them accordingly while taking care to keep indexing the arrays
in xdfile_t with absolute line numbers.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Helped-by: Phillip Wood
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Rewrite nested ternaries with a clear if/else ladder for
action1/action2 to improve readability while preserving
behavior.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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.
Helped-by: Phillip Wood
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Change the parameters of xdl_clean_mmatch() and the local variables
i, nm, mlim in xdl_cleanup_records() to use unambiguous types. Best
viewed with --color-words.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There is no real square root for a negative number and size_t may not
be large enough for certain applications, replace long with uint64_t.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Simplify the first 2 for loops by directly indexing the xdfile.recs.
recs is unused in the last 2 for loops, remove it. Best viewed with
--color-words.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Prior to commit 6d507bd41a (xdiff: delete fields ha, line, size
in xdlclass_t in favor of an xrecord_t, 2025-09-26) xdlclass_t
carried a copy of all the fields in xrecord_t. That commit embedded
xrecord_t in xdlclass_t to make it easier to change the types of
the fields in xrecord_t. However commit 6a26019c81 (xdiff: split
xrecord_t.ha into line_hash and minimal_perfect_hash, 2025-11-18)
added the "minimal_perfect_hash" field to xrecord_t which is not
used by xdlclass_t. To avoid wasting space stop copying the whole
of xrecord_t and just copy the pointer and length that we need to
intern the line. Together with the previous commit this effectively
reverts 6d507bd41a.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Prior to commit 6a26019c81 (xdiff: split xrecord_t.ha into line_hash
and minimal_perfect_hash, 2025-11-18) the "ha" field of xrecord_t
initially held the "line_hash" value and once the line had been
interned that field was updated to hold the "minimal_perfect_hash". The
"line_hash" is only used to intern the line so there is no point in
storing it after all the input lines have been interned.
Removing the "line_hash" field from xrecord_t and storing it in
xdlclass_t where it is actually used makes it clearer that it is a
temporary value and it should not be used once we're calculated the
"minimal_perfect_hash". This also reduces the size of xrecord_t by 25%
on 64-bit platforms and 40% on 32-bit platforms. While the struct is
small we create one instance per input line so any saving is welcome.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The classic diff adds only the lines that it's going to consider,
during the diff, to an array. A mapping between the compacted
array, and the lines of the file that they reference, is
facilitated by this array.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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size_t is used because nreff describes the number of elements in memory
for rindex.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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size_t is used because nrec describes the number of elements for both
recs, and for 'changed' + 2.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The ha field is serving two different purposes, which makes the code
harder to read. At first glance, it looks like many places assume
there could never be hash collisions between lines of the two input
files. In reality, line_hash is used together with xdl_recmatch() to
ensure correct comparisons of lines, even when collisions occur.
To make this clearer, the old ha field has been split:
* line_hash: a straightforward hash of a line, independent of any
external context. Its type is uint64_t, as it comes from a fixed
width hash function.
* minimal_perfect_hash: Not a new concept, but now a separate
field. It comes from the classifier's general-purpose hash table,
which assigns each line a unique and minimal hash across the two
files. A size_t is used here because it's meant to be used to
index an array. This also avoids ` as usize` casts on the Rust
side when using it to index a slice.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Convert the function signature and body to use unambiguous types. char
is changed to uint8_t because this function processes bytes in memory.
unsigned long to uint64_t so that the hash output is consistent across
platforms. `flags` was changed from long to uint64_t to ensure the
high order bits are not dropped on platforms that treat long as 32
bits.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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size_t is the appropriate type because size is describing the number of
elements, bytes in this case, in memory.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Make xrecord_t.ptr uint8_t because it's referring to bytes in memory.
In order to avoid a refactor avalanche, many uses of this field were
cast to char* or similar.
Places where casting was unnecessary:
xemit.c:156
xmerge.c:124
xmerge.c:127
xmerge.c:164
xmerge.c:169
xmerge.c:172
xmerge.c:178
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The only values possible for 'changed' is 1 and 0, which exactly maps
to a bool type. It might not look like this because action1 and action2
(which use to be dis1, and dis2) were also of type char and were
assigned numerical values within a few lines of 'changed' (what used to
be rchg).
Using DISCARD/KEEP/INVESTIGATE for action1[i]/action2[j], and true/false
for changed[k] makes it clear to future readers that these are
logically separate concepts.
Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This commit is refactor-only; no behavior is changed. A future commit
will use bool literals for changed[i].
The functions xdl_clean_mmatch() and xdl_cleanup_records() will be
cleaned up more in a future patch series. The changes to
xdl_cleanup_records(), in this patch, are just to make it clear why
`char rchg` is refactored to `bool changed`.
Rename dis* to action* and replace literal numericals with macros.
The old names came from when dis* (which I think was short for discard)
was treated like a boolean, but over time it grew into a ternary state
machine. The result was confusing because dis* and rchg* both used 0/1
values with different meanings.
The new names and macros make the states explicit. nm is short for
number of matches, and mlim is a heuristic limit:
nm == 0 -> action[i] = DISCARD -> changed[i] = true
0 < nm < mlim -> action[i] = KEEP -> changed[i] = false
nm >= mlim -> action[i] = INVESTIGATE -> changed[i] = xdl_clean_mmatch()
When need_min is true, only DISCARD and KEEP occur because the limit
is effectively infinite.
Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The field rchg (now 'changed') declares if a line in a file is changed
or not. A later commit will change it's type from 'char' to 'bool'
to make its purpose even more clear.
Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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xdfile_t currently uses chastore_t which is an arena allocator. I
think that xrecord_t used to be a linked list and recs didn't exist
originally. When recs was added I think they forgot to remove
xdfile_t.next, but was overlooked. This dual data structure setup
makes the code somewhat confusing.
Additionally the C type chastore_t isn't FFI friendly, and provides
little to no performance benefit over using realloc to grow an array.
Performance impact of deleting fields from xdfile_t:
Deleting ha is about 5% slower.
Deleting cha is about 5% faster.
Delete ha, but keep cha
time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_ha/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.269 s ± 0.017 s [User: 1.135 s, System: 0.128 s]
Range (min … max): 1.249 s … 1.286 s 10 runs
Benchmark 2: build_delete_ha/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.339 s ± 0.017 s [User: 1.234 s, System: 0.099 s]
Range (min … max): 1.320 s … 1.358 s 10 runs
Summary
build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
1.06 ± 0.02 times faster than build_delete_ha/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Delete cha, but keep ha
time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_chastore/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.290 s ± 0.001 s [User: 1.154 s, System: 0.130 s]
Range (min … max): 1.288 s … 1.292 s 10 runs
Benchmark 2: build_delete_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.232 s ± 0.017 s [User: 1.105 s, System: 0.121 s]
Range (min … max): 1.205 s … 1.249 s 10 runs
Summary
build_delete_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
1.05 ± 0.01 times faster than build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Delete ha AND chastore
time hyperfine --warmup 3 -L exe build_v2.51.0/git,build_delete_ha_and_chastore/git '{exe} log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null'
Benchmark 1: build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.291 s ± 0.002 s [User: 1.156 s, System: 0.129 s]
Range (min … max): 1.287 s … 1.295 s 10 runs
Benchmark 2: build_delete_ha_and_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Time (mean ± σ): 1.306 s ± 0.001 s [User: 1.195 s, System: 0.105 s]
Range (min … max): 1.305 s … 1.308 s 10 runs
Summary
build_v2.51.0/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null ran
1.01 ± 0.00 times faster than build_delete_ha_and_chastore/git log --oneline --shortstat --diff-algorithm=myers -3000 v2.39.1 >/dev/null
Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The fields from xdlclass_t are aliases of xrecord_t:
xdlclass_t.line -> xrecord_t.ptr
xdlclass_t.size -> xrecord_t.size
xdlclass_t.ha -> xrecord_t.ha
xdlclass_t carries a copy of the data in xrecord_t, but instead of
embedding xrecord_t it duplicates the individual fields. A future
commit will change the types used in xrecord_t so embed it in
xdlclass_t first, so we don't have to remember to change the types
here as well.
Best-viewed-with: --color-words
Helped-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When 0 <= i < xdfile_t.nreff the following is true:
xdfile_t.ha[i] == xdfile_t.recs[xdfile_t.rindex[i]]
This makes the code about 5% slower. The fields rindex and ha are
specific to the classic diff (myers and minimal). I plan on creating a
struct for classic diff, but there's a lot of cleanup that needs to be
done before that can happen and leaving ha in would make those cleanups
harder to follow.
A subsequent commit will delete the chastore cha from xdfile_t. That
later commit will investigate deleting ha and cha independently and
together.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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xrecord_t.next, xdfile_t.hbits, xdfile_t.rhash are initialized,
but never used for anything by the code. Remove them.
Best-viewed-with: --color-words
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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These local variables are essentially a hand-rolled additional
implementation of xdl_free_ctx() inlined into xdl_prepare_ctx(). Modify
the code to use the existing xdl_free_ctx() function so there aren't
two ways to free such variables.
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Move xdl_prepare_env() later in the file to avoid the need
for static forward declarations.
Best-viewed-with: --color-moved
Signed-off-by: Ezekiel Newren <ezekielnewren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The cleanup_records function marks some lines as changed before running
the actual diff algorithm. For most lines, this is a good performance
optimization, but it also marks lines that are surrounded by many
changed lines as changed as well. This can cause redundant changes and
longer-than-necessary diffs.
Whether this results in better-looking diffs is subjective. However, the
--minimal flag explicitly requests the shortest possible diff.
The change results in shorter diffs in about 1.3% of all diffs in Git's
history. Performance wise, I have measured the impact on
"git log -p -3000 --minimal > /dev/null". With this change, I get
Time (mean ± σ): 2.363 s ± 0.023 s (25 runs)
and without this patch I measured
Time (mean ± σ): 2.362 s ± 0.035 s (25 runs).
As the difference is well within the margin of error, this does not seem
to have an impact on performance.
Signed-off-by: Niels Glodny <n.glodny@campus.lmu.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a helper to grow an array. This is analogous to ALLOC_GROW() in
the rest of the codebase but returns −1 on allocation failure to
accommodate other users of libxdiff such as libgit2. It will also
return a error if the multiplication overflows while calculating the
new allocation size. Note that this keeps doubling on reallocation
like the code it is replacing rather than increasing the existing size
by half like ALLOC_GROW(). It does however copy ALLOC_GROW()'s trick
of adding a small amount to the new allocation to avoid a lot of
reallocations at small sizes.
Note that xdl_alloc_grow_helper() uses long rather than size_t for
`nr` and `alloc` to match the existing code.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a helper for allocating an array and initialize the elements to
zero. This is analogous to CALLOC_ARRAY() in the rest of the codebase
but it returns NULL on allocation failures rather than dying to
accommodate other users of libxdiff such as libgit2.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In preparation for introducing XDL_CALLOC_ARRAY() use calloc() to
obtain zeroed out memory rather than malloc() followed by memset(). To
try and keep the lines a reasonable length this commit also stops
casting the pointer returned by calloc() as this is unnecessary.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a helper to allocate an array that automatically calculates the
allocation size. This is analogous to ALLOC_ARRAY() in the rest of the
codebase but returns NULL if the allocation fails to accommodate other
users of libxdiff such as libgit2. The helper will also return NULL if
the multiplication in the allocation calculation overflows.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* ep/maint-equals-null-cocci:
tree-wide: apply equals-null.cocci
contrib/coccinnelle: add equals-null.cocci
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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rindex and ha are only used by xdl_cleanup_records() which is not
called by the histogram or patience algorithms. The perf test results
show a small reduction in run time but that is probably within the
noise.
Test HEAD^ HEAD
-----------------------------------------------------------------------------
4000.1: log -3000 (baseline) 0.19(0.17+0.02) 0.19(0.12+0.07) +0.0%
4000.2: log --raw -3000 (tree-only) 0.98(0.78+0.20) 0.98(0.81+0.16) +0.0%
4000.3: log -p -3000 (Myers) 4.81(4.15+0.64) 4.81(4.23+0.56) +0.0%
4000.4: log -p -3000 --histogram 5.87(5.19+0.66) 5.83(5.11+0.70) -0.7%
4000.5: log -p -3000 --patience 5.35(4.60+0.73) 5.31(4.61+0.69) -0.7%
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The mailing address for the FSF has changed over the years. Rather than
updating the address across all files, refer readers to gnu.org, as the
GNU GPL documentation now suggests for license notices. The mailing
address is retained in the full license files (COPYING and LGPL-2.1).
The old address is still present in t/diff-lib/COPYING. This is
intentional, as the file is used in tests and the contents are not
expected to change.
Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The xdl_prepare_env() function may initialise an xdlclassifier_t
data structure via xdl_init_classifier(), which allocates memory
to several fields, for example 'rchash', 'rcrecs' and 'ncha'.
If this function later exits due to the failure of xdl_optimize_ctxs(),
then this xdlclassifier_t structure, and the memory allocated to it,
is not cleaned up.
In order to fix the memory leak, insert a call to xdl_free_classifier()
before returning.
Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Commit 307ab20b3 ("xdiff: PATIENCE/HISTOGRAM are not independent option
bits", 19-02-2012) introduced the XDF_DIFF_ALG() macro to access the
flag bits used to represent the diff algorithm requested. In addition,
code which had used explicit manipulation of the flag bits was changed
to use the macros.
However, one example of direct manipulation remains. Update this code to
use the XDF_DIFF_ALG() macro.
Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Because the default Myers, patience and histogram algorithms cannot be in
effect at the same time, XDL_PATIENCE_DIFF and XDL_HISTOGRAM_DIFF are not
independent bits. Instead of wasting one bit per algorithm, define a few
macros to access the few bits they occupy and update the code that access
them.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* rs/diff-cleanup-records-fix:
diff: resurrect XDF_NEED_MINIMAL with --minimal
Revert removal of multi-match discard heuristic in 27af01
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27af01d (xdiff/xprepare: improve O(n*m) performance in
xdl_cleanup_records(), 2011-08-17) was supposed to be a performance
boost only. However, it unexpectedly changed the behaviour of diff.
Revert a part of 27af01d that removes logic that mark lines as
"multi-match" (ie. dis[i] == 2). This was preventing the multi-match
discard heuristic (performed in xdl_cleanup_records() and
xdl_clean_mmatch()) from executing.
Reported-by: Alexander Pepper <pepper@inf.fu-berlin.de>
Signed-off-by: René Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* rc/histogram-diff:
xdiff/xprepare: initialise xdlclassifier_t cf in xdl_prepare_env()
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Ensure that the xdl_free_classifier() call on xdlclassifier_t cf is safe
even if xdl_init_classifier() isn't called. This may occur in the case
where diff is run with --histogram and a call to, say, xdl_prepare_ctx()
fails.
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* rc/histogram-diff:
xdiff/xhistogram: drop need for additional variable
xdiff/xhistogram: rely on xdl_trim_ends()
xdiff/xhistogram: rework handling of recursed results
xdiff: do away with xdl_mmfile_next()
Make test number unique
xdiff/xprepare: use a smaller sample size for histogram diff
xdiff/xprepare: skip classification
teach --histogram to diff
t4033-diff-patience: factor out tests
xdiff/xpatience: factor out fall-back-diff function
xdiff/xprepare: refactor abort cleanups
xdiff/xprepare: use memset()
Conflicts:
xdiff/xprepare.c
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In xdl_cleanup_records(), we see O(n*m) performance, where n is the
number of records from xdf->dstart to xdf->dend, and m is the size of a
bucket in xdf->rhash (<= by mlim).
Here, we improve this to O(n) by pre-computing nm (in rcrec->len(1|2))
in xdl_classify_record().
Reported-by: Marat Radchenko <marat@slonopotamus.org>
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Given our simple mmfile structure, xdl_mmfile_next() calls are
redundant. Do away with calls to them.
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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>
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xdiff performs "classification" of records (xdl_classify_record()),
replacing hashes (xrecord_t.ha) with a unique identifier of the
record/line and building a hash table (xrecord_t.rhash) of records. This
is then used to "cleanup" records (xdl_cleanup_records()).
We don't need any of that in histogram diff, so we omit calls to these
functions. We also skip allocating memory to the hash table, rhash, as
it is no longer used.
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>
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