git/commit-reach.h

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#ifndef COMMIT_REACH_H
#define COMMIT_REACH_H
commit-reach.h: add missing declarations (hdr-check) Add the necessary #includes and forward declarations to allow the header file to pass the 'hdr-check' target. Note that, since this header includes the commit-slab implementation header file (indirectly via commit-slab.h), some of the commit-slab inline functions (e.g contains_cache_at_peek()) will not compile without the complete type of 'struct commit'. Hence, we replace the forward declaration of 'struct commit' with the an #include of the 'commit.h' header file. It is possible, using the 'commit-slab-{decl,impl}.h' files, to avoid this inclusion of the 'commit.h' header. Commit a9f1f1f9f8 ("commit-slab.h: code split", 2018-05-19) separated the commit-slab interface from its implementation, to allow for the definition of a public commit-slab data structure. This enabled us to avoid including the commit-slab implementation in a header file, which could result in the replication of the commit-slab functions in each compilation unit in which it was included. Indeed, if you compile with optimizations disabled, then run this script: $ cat -n dup-static.sh 1 #!/bin/sh 2 3 nm $1 | grep ' t ' | cut -d' ' -f3 | sort | uniq -c | 4 sort -rn | grep -v ' 1' $ $ ./dup-static.sh git | grep contains 24 init_contains_cache_with_stride 24 init_contains_cache 24 contains_cache_peek 24 contains_cache_at_peek 24 contains_cache_at 24 clear_contains_cache $ you will find 24 copies of the commit-slab routines for the contains_cache. Of course, when you enable optimizations again, these duplicate static functions (mostly) disappear. Compiling with gcc at -O2, leaves two static functions, thus: $ nm commit-reach.o | grep contains_cache 0000000000000870 t contains_cache_at_peek.isra.1.constprop.6 $ nm ref-filter.o | grep contains_cache 00000000000002b0 t clear_contains_cache.isra.14 $ However, using a shared 'contains_cache' would result in all six of the above functions as external public functions in the git binary. At present, only three of these functions are actually called, so the trade-off seems to favour letting the compiler inline the commit-slab functions. Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-10-27 01:53:57 +00:00
#include "commit.h"
#include "commit-slab.h"
struct commit_list;
struct ref_filter;
commit-reach.h: add missing declarations (hdr-check) Add the necessary #includes and forward declarations to allow the header file to pass the 'hdr-check' target. Note that, since this header includes the commit-slab implementation header file (indirectly via commit-slab.h), some of the commit-slab inline functions (e.g contains_cache_at_peek()) will not compile without the complete type of 'struct commit'. Hence, we replace the forward declaration of 'struct commit' with the an #include of the 'commit.h' header file. It is possible, using the 'commit-slab-{decl,impl}.h' files, to avoid this inclusion of the 'commit.h' header. Commit a9f1f1f9f8 ("commit-slab.h: code split", 2018-05-19) separated the commit-slab interface from its implementation, to allow for the definition of a public commit-slab data structure. This enabled us to avoid including the commit-slab implementation in a header file, which could result in the replication of the commit-slab functions in each compilation unit in which it was included. Indeed, if you compile with optimizations disabled, then run this script: $ cat -n dup-static.sh 1 #!/bin/sh 2 3 nm $1 | grep ' t ' | cut -d' ' -f3 | sort | uniq -c | 4 sort -rn | grep -v ' 1' $ $ ./dup-static.sh git | grep contains 24 init_contains_cache_with_stride 24 init_contains_cache 24 contains_cache_peek 24 contains_cache_at_peek 24 contains_cache_at 24 clear_contains_cache $ you will find 24 copies of the commit-slab routines for the contains_cache. Of course, when you enable optimizations again, these duplicate static functions (mostly) disappear. Compiling with gcc at -O2, leaves two static functions, thus: $ nm commit-reach.o | grep contains_cache 0000000000000870 t contains_cache_at_peek.isra.1.constprop.6 $ nm ref-filter.o | grep contains_cache 00000000000002b0 t clear_contains_cache.isra.14 $ However, using a shared 'contains_cache' would result in all six of the above functions as external public functions in the git binary. At present, only three of these functions are actually called, so the trade-off seems to favour letting the compiler inline the commit-slab functions. Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-10-27 01:53:57 +00:00
struct object_id;
struct object_array;
struct commit_list *get_merge_bases_many(struct commit *one,
int n,
struct commit **twos);
struct commit_list *get_merge_bases_many_dirty(struct commit *one,
int n,
struct commit **twos);
struct commit_list *get_merge_bases(struct commit *one, struct commit *two);
struct commit_list *get_octopus_merge_bases(struct commit_list *in);
/* To be used only when object flags after this call no longer matter */
struct commit_list *get_merge_bases_many_dirty(struct commit *one, int n, struct commit **twos);
int is_descendant_of(struct commit *commit, struct commit_list *with_commit);
int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit **reference);
int in_merge_bases(struct commit *commit, struct commit *reference);
/*
* Takes a list of commits and returns a new list where those
* have been removed that can be reached from other commits in
* the list. It is useful for, e.g., reducing the commits
* randomly thrown at the git-merge command and removing
* redundant commits that the user shouldn't have given to it.
*
* This function destroys the STALE bit of the commit objects'
* flags.
*/
struct commit_list *reduce_heads(struct commit_list *heads);
/*
* Like `reduce_heads()`, except it replaces the list. Use this
* instead of `foo = reduce_heads(foo);` to avoid memory leaks.
*/
void reduce_heads_replace(struct commit_list **heads);
int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid);
/*
* Unknown has to be "0" here, because that's the default value for
* contains_cache slab entries that have not yet been assigned.
*/
enum contains_result {
CONTAINS_UNKNOWN = 0,
CONTAINS_NO,
CONTAINS_YES
};
define_commit_slab(contains_cache, enum contains_result);
int commit_contains(struct ref_filter *filter, struct commit *commit,
struct commit_list *list, struct contains_cache *cache);
/*
* Determine if every commit in 'from' can reach at least one commit
* that is marked with 'with_flag'. As we traverse, use 'assign_flag'
* as a marker for commits that are already visited. Do not walk
commit-reach: make can_all_from_reach... linear The can_all_from_reach_with_flags() algorithm is currently quadratic in the worst case, because it calls the reachable() method for every 'from' without tracking which commits have already been walked or which can already reach a commit in 'to'. Rewrite the algorithm to walk each commit a constant number of times. We also add some optimizations that should work for the main consumer of this method: fetch negotitation (haves/wants). The first step includes using a depth-first-search (DFS) from each 'from' commit, sorted by ascending generation number. We do not walk beyond the minimum generation number or the minimum commit date. This DFS is likely to be faster than the existing reachable() method because we expect previous ref values to be along the first-parent history. If we find a target commit, then we mark everything in the DFS stack as a RESULT. This expands the set of targets for the other 'from' commits. We also mark the visited commits using 'assign_flag' to prevent re- walking the same commits. We still need to clear our flags at the end, which is why we will have a total of three visits to each commit. Performance was measured on the Linux repository using 'test-tool reach can_all_from_reach'. The input included rows seeded by tag values. The "small" case included X-rows as v4.[0-9]* and Y-rows as v3.[0-9]*. This mimics a (very large) fetch that says "I have all major v3 releases and want all major v4 releases." The "large" case included X-rows as "v4.*" and Y-rows as "v3.*". This adds all release-candidate tags to the set, which does not greatly increase the number of objects that are considered, but does increase the number of 'from' commits, demonstrating the quadratic nature of the previous code. Small Case: Before: 1.52 s After: 0.26 s Large Case: Before: 3.50 s After: 0.27 s Note how the time increases between the two cases in the two versions. The new code increases relative to the number of commits that need to be walked, but not directly relative to the number of 'from' commits. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-07-20 16:33:28 +00:00
* commits with date below 'min_commit_date' or generation below
* 'min_generation'.
*/
int can_all_from_reach_with_flag(struct object_array *from,
unsigned int with_flag,
unsigned int assign_flag,
commit-reach: make can_all_from_reach... linear The can_all_from_reach_with_flags() algorithm is currently quadratic in the worst case, because it calls the reachable() method for every 'from' without tracking which commits have already been walked or which can already reach a commit in 'to'. Rewrite the algorithm to walk each commit a constant number of times. We also add some optimizations that should work for the main consumer of this method: fetch negotitation (haves/wants). The first step includes using a depth-first-search (DFS) from each 'from' commit, sorted by ascending generation number. We do not walk beyond the minimum generation number or the minimum commit date. This DFS is likely to be faster than the existing reachable() method because we expect previous ref values to be along the first-parent history. If we find a target commit, then we mark everything in the DFS stack as a RESULT. This expands the set of targets for the other 'from' commits. We also mark the visited commits using 'assign_flag' to prevent re- walking the same commits. We still need to clear our flags at the end, which is why we will have a total of three visits to each commit. Performance was measured on the Linux repository using 'test-tool reach can_all_from_reach'. The input included rows seeded by tag values. The "small" case included X-rows as v4.[0-9]* and Y-rows as v3.[0-9]*. This mimics a (very large) fetch that says "I have all major v3 releases and want all major v4 releases." The "large" case included X-rows as "v4.*" and Y-rows as "v3.*". This adds all release-candidate tags to the set, which does not greatly increase the number of objects that are considered, but does increase the number of 'from' commits, demonstrating the quadratic nature of the previous code. Small Case: Before: 1.52 s After: 0.26 s Large Case: Before: 3.50 s After: 0.27 s Note how the time increases between the two cases in the two versions. The new code increases relative to the number of commits that need to be walked, but not directly relative to the number of 'from' commits. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-07-20 16:33:28 +00:00
time_t min_commit_date,
uint32_t min_generation);
int can_all_from_reach(struct commit_list *from, struct commit_list *to,
int commit_date_cutoff);
commit-reach: implement get_reachable_subset The existing reachability algorithms in commit-reach.c focus on finding merge-bases or determining if all commits in a set X can reach at least one commit in a set Y. However, for two commits sets X and Y, we may also care about which commits in Y are reachable from at least one commit in X. Implement get_reachable_subset() which answers this question. Given two arrays of commits, 'from' and 'to', return a commit_list with every commit from the 'to' array that is reachable from at least one commit in the 'from' array. The algorithm is a simple walk starting at the 'from' commits, using the PARENT2 flag to indicate "this commit has already been added to the walk queue". By marking the 'to' commits with the PARENT1 flag, we can determine when we see a commit from the 'to' array. We remove the PARENT1 flag as we add that commit to the result list to avoid duplicates. The order of the resulting list is a reverse of the order that the commits are discovered in the walk. There are a couple shortcuts to avoid walking more than we need: 1. We determine the minimum generation number of commits in the 'to' array. We do not walk commits with generation number below this minimum. 2. We count how many distinct commits are in the 'to' array, and decrement this count when we discover a 'to' commit during the walk. If this number reaches zero, then we can terminate the walk. Tests will be added using the 'test-tool reach' helper in a subsequent commit. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-11-02 13:14:45 +00:00
/*
* Return a list of commits containing the commits in the 'to' array
* that are reachable from at least one commit in the 'from' array.
* Also add the given 'flag' to each of the commits in the returned list.
*
* This method uses the PARENT1 and PARENT2 flags during its operation,
* so be sure these flags are not set before calling the method.
*/
struct commit_list *get_reachable_subset(struct commit **from, int nr_from,
struct commit **to, int nr_to,
unsigned int reachable_flag);
#endif