diff options
author | Stephan Beyer <s-beyer@gmx.net> | 2016-04-10 15:19:12 +0200 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2016-04-15 12:27:29 -0700 |
commit | 809b1f4fbc070ad398459685eb43dd8f415d5ee6 (patch) | |
tree | cd0509c04b47349ac1e154e582405cd791d36ee6 | |
parent | 0d3d93ae0f18666bb6b5dd2cda1995569215ffd9 (diff) | |
download | git-809b1f4fbc070ad398459685eb43dd8f415d5ee6.tar.gz |
bisect: use a bottom-up traversal to find relevant weights
The idea is to reverse the DAG and perform a traversal
starting on all sources of the reversed DAG.
We walk from the bottom commits, incrementing the weight while
walking on a part of the graph that is single strand of pearls,
or doing the "count the reachable ones the hard way" using
compute_weight() when we hit a merge commit.
A traversal ends when the computed weight is falling or halfway.
This way, commits with too high weight to be relevant are never
visited (and their weights are never computed).
Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
-rw-r--r-- | bisect.c | 226 |
1 files changed, 150 insertions, 76 deletions
@@ -30,6 +30,9 @@ static unsigned marker; struct node_data { int weight; unsigned marked; + unsigned parents; + unsigned visited : 1; + struct commit_list *children; }; #define DEBUG_BISECT 0 @@ -110,16 +113,6 @@ static int count_interesting_parents(struct commit *commit) return count; } -static inline int halfway(struct commit *commit) -{ - /* - * Don't short-cut something we are not going to return! - */ - if (commit->object.flags & TREESAME) - return 0; - return !distance_direction(commit); -} - #if !DEBUG_BISECT #define show_list(a,b,c) do { ; } while (0) #else @@ -340,90 +333,168 @@ static void compute_all_weights(struct commit_list *list, show_list("bisection 2 counted all", counted, list); } -/* At the moment this is basically the same as compute_all_weights() - * but with a halfway shortcut */ -static void compute_relevant_weights(struct commit_list *list, - struct node_data *weights) +static struct commit_list *build_reversed_dag(struct commit_list *list, + struct node_data *nodes) { - int n, counted; + struct commit_list *sources = NULL; struct commit_list *p; - - counted = 0; - - for (n = 0, p = list; p; p = p->next) { + int n = 0; + for (p = list; p; p = p->next) + p->item->util = &nodes[n++]; + for (p = list; p; p = p->next) { + struct commit_list *parent; struct commit *commit = p->item; - unsigned flags = commit->object.flags; - - commit->util = &weights[n++]; - switch (count_interesting_parents(commit)) { - case 0: - if (!(flags & TREESAME)) { - node_data(commit)->weight = 1; - counted++; - show_list("bisection 2 count one", - counted, list); + for (parent = commit->parents; parent; parent = parent->next) { + if (!(parent->item->object.flags & UNINTERESTING)) { + struct commit_list **next = &node_data(parent->item)->children; + commit_list_insert(commit, next); + node_data(commit)->parents++; } - break; - case 1: - node_data(commit)->weight = -1; - break; - default: - node_data(commit)->weight = -2; - break; } } - show_list("bisection 2 initialize", counted, list); - + /* find all sources */ for (p = list; p; p = p->next) { - if (!(p->item->object.flags & UNINTERESTING) - && (node_data(p->item)->weight == -2)) { - compute_weight(p->item); + if (node_data(p->item)->parents == 0) + commit_list_insert(p->item, &sources); + } - /* Does it happen to be at exactly half-way? */ - if (halfway(p->item)) - return; - counted++; + return sources; +} + +static inline void commit_list_insert_unique(struct commit *item, + struct commit_list **list) +{ + if (!*list || item < (*list)->item) /* empty list or item will be first */ + commit_list_insert(item, list); + else if (item != (*list)->item) { /* item will not be first or not inserted */ + struct commit_list *p = *list; + for (; p->next && p->next->item < item; p = p->next); + if (!p->next || item != p->next->item) /* not already inserted */ + commit_list_insert(item, &p->next); + } +} + +/* do a traversal on the reversed DAG (starting from commits in queue), + * but stop at merge commits */ +static void traversal_up_to_merges(struct commit_list *queue, + struct commit_list **merges) +{ + assert(queue); + while (queue) { + struct commit *top = queue->item; + struct commit_list *p; + + pop_commit(&queue); + + if (distance_direction(top) > 0) { + node_data(top)->visited = 1; + + /* queue children */ + for (p = node_data(top)->children; p; p = p->next) { + if (node_data(p->item)->parents > 1) /* child is a merge */ + commit_list_insert_unique(p->item, merges); + else { + node_data(p->item)->weight = node_data(top)->weight; + if (!(p->item->object.flags & TREESAME)) + node_data(p->item)->weight++; + commit_list_insert(p->item, &queue); + } + } } } +} - show_list("bisection 2 compute_weight", counted, list); +static inline int all_parents_are_visited(struct commit *merge) +{ + struct commit_list *p; + for (p = merge->parents; p; p = p->next) { + if (p->item->util && !node_data(p->item)->visited) + return 0; + } + return 1; +} - while (counted < total) { - for (p = list; p; p = p->next) { - struct commit_list *q; - unsigned flags = p->item->object.flags; +static struct commit *extract_merge_to_queue(struct commit_list **merges) +{ + assert(merges); - if (0 <= node_data(p->item)->weight) - continue; - for (q = p->item->parents; q; q = q->next) { - if (q->item->object.flags & UNINTERESTING) - continue; - if (0 <= node_data(q->item)->weight) - break; - } - if (!q) - continue; + struct commit_list *p, *q; + struct commit *found; - /* - * weight for p is unknown but q is known. - * add one for p itself if p is to be counted, - * otherwise inherit it from q directly. - */ - node_data(p->item)->weight = node_data(q->item)->weight; - if (!(flags & TREESAME)) { - node_data(p->item)->weight++; - counted++; - show_list("bisection 2 count one", - counted, list); - } + /* find a merge that is ready, i.e. all parents have been computed */ + for (q = NULL, p = *merges; p && !all_parents_are_visited(p->item); + q = p, p = p->next); + if (!p) + return NULL; - /* Does it happen to be at exactly half-way? */ - if (halfway(p->item)) - return; + /* remove that commit from the list and return it */ + if (q) { + assert(q->next == p); + q->next = p->next; + } else /* found first element of list */ + *merges = p->next; + found = p->item; + free(p); + + return found; +} + +static inline int find_new_queue_from_merges(struct commit_list **queue, + struct commit_list **merges) +{ + if (*merges) { + struct commit *merge = extract_merge_to_queue(merges); + *queue = NULL; + if (merge) { + commit_list_insert(merge, queue); + return 1; } } - show_list("bisection 2 counted all", counted, list); + return 0; +} + +static inline void compute_merge_weights(struct commit_list *merges) +{ + struct commit_list *p; + for (p = merges; p; p = p->next) + compute_weight(p->item); +} + +static void bottom_up_traversal(struct commit_list *queue) +{ + struct commit_list *merges = NULL; + traversal_up_to_merges(queue, &merges); + while (find_new_queue_from_merges(&queue, &merges)) { + compute_merge_weights(queue); + traversal_up_to_merges(queue, &merges); + } + + /* cleanup */ + free_commit_list(merges); +} + +/* The idea is to reverse the DAG and perform a modified breadth-first search + * on it, starting on all sources of the reversed DAG. + * Before each visit of a commit, its weight is induced. + * This only works for non-merge commits, so the traversal stops prematurely on + * merge commits (that are collected in a list). + * Merge commits from that collection are considered for further visits + * as soon as all parents have been visited. + * Their weights are computed using compute_weight(). + * Each traversal ends when the computed weight is falling or halfway. + */ +static void compute_relevant_weights(struct commit_list *list, + struct node_data *weights) +{ + struct commit_list *p; + struct commit_list *sources = build_reversed_dag(list, weights); + + for (p = sources; p; p = p->next) + node_data(p->item)->weight = 1; + bottom_up_traversal(sources); + + show_list("bisection 3 result", total, list); } struct commit_list *find_bisection(struct commit_list *list, @@ -470,8 +541,11 @@ struct commit_list *find_bisection(struct commit_list *list, compute_all_weights(list, weights); best = best_bisection_sorted(list); } else { + int i; compute_relevant_weights(list, weights); best = best_bisection(list); + for (i = 0; i < on_list; i++) /* cleanup */ + free_commit_list(weights[i].children); } assert(best); *reaches = node_data(best->item)->weight; |