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2024-05-24ewah: `bitmap_equals_ewah()`Taylor Blau1-0/+19
Prepare to reuse existing pseudo-merge bitmaps by implementing a `bitmap_equals_ewah()` helper. This helper will be used to see if a raw bitmap (containing the set of parents for some pseudo-merge) is equal to any existing pseudo-merge's commits bitmap (which are stored as EWAH-compressed bitmaps on disk). Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-24ewah: implement `ewah_bitmap_popcount()`Taylor Blau1-0/+14
Some of the pseudo-merge test helpers (which will be introduced in the following commit) will want to indicate the total number of commits in or objects reachable from a pseudo-merge. Implement a popcount() function that operates on EWAH bitmaps to quickly determine how many bits are set in each of the respective bitmaps. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-05-24ewah: implement `ewah_bitmap_is_subset()`Taylor Blau1-0/+43
In order to know whether a given pseudo-merge (comprised of a "parents" and "objects" bitmaps) is "satisfied" and can be OR'd into the bitmap result, we need to be able to quickly determine whether the "parents" bitmap is a subset of the current set of objects reachable on either side of a traversal. Implement a helper function to prepare for that, which determines whether an EWAH bitmap (the parents bitmap from the pseudo-merge) is a subset of a non-EWAH bitmap (in this case, the results bitmap from either side of the traversal). This function makes use of the EWAH iterator to avoid inflating any part of the EWAH bitmap after we determine it is not a subset of the non-EWAH bitmap. This "fail-fast" allows us to avoid a potentially large amount of wasted effort. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-14ewah: implement `bitmap_is_empty()`Taylor Blau1-0/+9
In a future commit, we will want to check whether or not a bitmap has any bits set in any of its words. The best way to do this (prior to the existence of this patch) is to call `bitmap_popcount()` and check whether the result is non-zero. But this is semi-wasteful, since we do not need to know the exact number of bits set, only whether or not there is at least one of them. Implement a new helper function to check just that. Suggested-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-07-05git-compat-util: move alloc macros to git-compat-util.hCalvin Wan1-1/+0
alloc_nr, ALLOC_GROW, and ALLOC_GROW_BY are commonly used macros for dynamic array allocation. Moving these macros to git-compat-util.h with the other alloc macros focuses alloc.[ch] to allocation for Git objects and additionally allows us to remove inclusions to alloc.h from files that solely used the above macros. Signed-off-by: Calvin Wan <calvinwan@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-02-23alloc.h: move ALLOC_GROW() functions from cache.hElijah Newren1-1/+2
This allows us to replace includes of cache.h with includes of the much smaller alloc.h in many places. It does mean that we also need to add includes of alloc.h in a number of C files. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-05-20Merge branch 'ep/maint-equals-null-cocci'Junio C Hamano1-1/+1
Introduce and apply coccinelle rule to discourage an explicit comparison between a pointer and NULL, and applies the clean-up to the maintenance track. * ep/maint-equals-null-cocci: tree-wide: apply equals-null.cocci tree-wide: apply equals-null.cocci contrib/coccinnelle: add equals-null.cocci
2022-05-02tree-wide: apply equals-null.cocciJunio C Hamano1-1/+1
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-04-01pack-bitmap-write: remove unused bitmap_reset() functionÆvar Arnfjörð Bjarmason1-5/+0
This function hasn't been used since 449fa5ee069 (pack-bitmap-write: ignore BITMAP_FLAG_REUSE, 2020-12-08), which was a cleanup commit intending to get rid of the code around the reusing of bitmaps. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-13use CALLOC_ARRAYRené Scharfe1-1/+1
Add and apply a semantic patch for converting code that open-codes CALLOC_ARRAY to use it instead. It shortens the code and infers the element size automatically. Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-08bitmap: implement bitmap_is_subset()Derrick Stolee1-0/+21
The bitmap_is_subset() function checks if the 'self' bitmap contains any bitmaps that are not on in the 'other' bitmap. Up until this patch, it had a declaration, but no implementation or callers. A subsequent patch will want this function, so implement it here. Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-08ewah: add bitmap_dup() functionJeff King1-0/+7
There's no easy way to make a copy of a bitmap. Obviously a caller can iterate over the bits and set them one by one in a new bitmap, but we can go much faster by copying whole words with memcpy(). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-08ewah: implement bitmap_or()Jeff King1-0/+9
We have a function to bitwise-OR an ewah into an uncompressed bitmap, but not to OR two uncompressed bitmaps. Let's add it. Interestingly, we have a public header declaration going back to e1273106f6 (ewah: compressed bitmap implementation, 2013-11-14), but the function was never implemented. That was all OK since there were no users of 'bitmap_or()', but a first caller will be added in a couple of patches. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-08ewah: make bitmap growth less aggressiveJeff King1-7/+4
If you ask to set a bit in the Nth word and we haven't yet allocated that many slots in our array, we'll increase the bitmap size to 2*N. This means we might frequently end up with bitmaps that are twice the necessary size (as soon as you ask for the biggest bit, we'll size up to twice that). But if we just allocate as many words as were asked for, we may not grow fast enough. The worst case there is setting bit 0, then 1, etc. Each time we grow we'd just extend by one more word, giving us linear reallocations (and quadratic memory copies). A middle ground is relying on alloc_nr(), which causes us to grow by a factor of roughly 3/2 instead of 2. That's less aggressive than doubling, and it may help avoid fragmenting memory. (If we start with N, then grow twice, our total is N*(3/2)^2 = 9N/4. After growing twice, that array of size 9N/4 can fit into the space vacated by the original array and first growth, N+3N/2 = 10N/4 > 9N/4, leading to less fragmentation in memory). Our worst case is still 3/2N wasted bits (you set bit N-1, then setting bit N causes us to grow by 3/2), but our average should be much better. This isn't usually that big a deal, but it will matter as we shift the reachability bitmap generation code to store more bitmaps in memory. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-08ewah: factor out bitmap growthJeff King1-5/+9
We auto-grow bitmaps when somebody asks to set a bit whose position is outside of our currently allocated range. Other operations besides single bit-setting might need to do this, too, so let's pull it into its own function. Note that we change the semantics a little: you now ask for the number of words you'd like to have, not the id of the block you'd like to write to. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-03-02Merge branch 'jk/object-filter-with-bitmap'Junio C Hamano1-0/+8
The object reachability bitmap machinery and the partial cloning machinery were not prepared to work well together, because some object-filtering criteria that partial clones use inherently rely on object traversal, but the bitmap machinery is an optimization to bypass that object traversal. There however are some cases where they can work together, and they were taught about them. * jk/object-filter-with-bitmap: rev-list --count: comment on the use of count_right++ pack-objects: support filters with bitmaps pack-bitmap: implement BLOB_LIMIT filtering pack-bitmap: implement BLOB_NONE filtering bitmap: add bitmap_unset() function rev-list: use bitmap filters for traversal pack-bitmap: basic noop bitmap filter infrastructure rev-list: allow commit-only bitmap traversals t5310: factor out bitmap traversal comparison rev-list: allow bitmaps when counting objects rev-list: make --count work with --objects rev-list: factor out bitmap-optimized routines pack-bitmap: refuse to do a bitmap traversal with pathspecs rev-list: fallback to non-bitmap traversal when filtering pack-bitmap: fix leak of haves/wants object lists pack-bitmap: factor out type iterator initialization
2020-02-14bitmap: add bitmap_unset() functionJeff King1-0/+8
We've never needed to unset an individual bit in a bitmap until now. Typically they start with all bits unset and we bitmap_set() them, or we are applying another bitmap as a mask. But the easiest way to apply an object filter to a bitmap result will be to unset the individual bits. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-01-23ewah/bitmap: introduce bitmap_word_alloc()Jeff King1-4/+9
In a following commit we will need to allocate a variable number of bitmap words, instead of always 32, so let's add bitmap_word_alloc() for this purpose. Note that we have to adjust the block growth in bitmap_set(), since a caller could now use an initial size of "0" (we don't plan to do that, but it doesn't hurt to be defensive). Helped-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-18ewah/bitmap.c: delete unused 'bitmap_each_bit()'Derrick Stolee1-24/+0
Reported-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-18ewah/bitmap.c: delete unused 'bitmap_clear()'Derrick Stolee1-8/+0
Reported-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-11-09Replace Free Software Foundation address in license noticesTodd Zullinger1-2/+1
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>
2016-02-22ewah: convert to REALLOC_ARRAY, etcJeff King1-12/+4
Now that we're built around xmalloc and friends, we can use helpers like REALLOC_ARRAY, ALLOC_GROW, and so on to make the code shorter and protect against integer overflow. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-22convert ewah/bitmap code to use xmallocJeff King1-6/+6
This code was originally written with the idea that it could be spun off into its own ewah library, and uses the overrideable ewah_malloc to do allocations. We plug in xmalloc as our ewah_malloc, of course. But over the years the ewah code itself has become more entangled with git, and the return value of many ewah_malloc sites is not checked. Let's just drop the level of indirection and use xmalloc and friends directly. This saves a few lines, and will let us adapt these sites to our more advanced malloc helpers. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-06-03ewah: use less generic macro nameJeff King1-6/+6
The ewah/ewok.h header pollutes the global namespace with "BITS_IN_WORD", without any specific notion that we are talking about the bits in an eword_t. We can give this the more specific name "BITS_IN_EWORD". Signed-off-by: Jeff King <peff@peff.net> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-06-03ewah/bitmap: silence warning about MASK macro redefinitionEric Sunshine1-8/+8
On PowerPC Mac OS X (10.5.8 "Leopard" with Xcode 3.1), system header /usr/include/ppc/param.h[1] pollutes the preprocessor namespace with a macro generically named MASK. This conflicts with the same-named macro in ewah/bitmap.c. We can avoid this conflict by using a more specific name. [1]: Included indirectly via: git-compat-util.h -> sys/sysctl.h -> sys/ucred.h -> sys/param.h -> machine/param.h -> ppc/param.h Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30ewah: compressed bitmap implementationVicent Marti1-0/+221
EWAH is a word-aligned compressed variant of a bitset (i.e. a data structure that acts as a 0-indexed boolean array for many entries). It uses a 64-bit run-length encoding (RLE) compression scheme, trading some compression for better processing speed. The goal of this word-aligned implementation is not to achieve the best compression, but rather to improve query processing time. As it stands right now, this EWAH implementation will always be more efficient storage-wise than its uncompressed alternative. EWAH arrays will be used as the on-disk format to store reachability bitmaps for all objects in a repository while keeping reasonable sizes, in the same way that JGit does. This EWAH implementation is a mostly straightforward port of the original `javaewah` library that JGit currently uses. The library is self-contained and has been embedded whole (4 files) inside the `ewah` folder to ease redistribution. The library is re-licensed under the GPLv2 with the permission of Daniel Lemire, the original author. The source code for the C version can be found on GitHub: https://github.com/vmg/libewok The original Java implementation can also be found on GitHub: https://github.com/lemire/javaewah [jc: stripped debug-only code per Peff's $gmane/239768] Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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