7fc0675f35
Update substring search to use the Two Way algorithm To improve our substring search performance, revive the two way searcher and adapt it to the Pattern API. Fixes #25483, a performance bug: that particular case now completes faster in optimized rust than in ruby (but they share the same order of magnitude). Many thanks to @gereeter who helped me understand the reverse case better and wrote the comment explaining `next_back` in the code. I had quickcheck to fuzz test forward and reverse searching thoroughly. The two way searcher implements both forward and reverse search, but not double ended search. The forward and reverse parts of the two way searcher are completely independent. The two way searcher algorithm has very small, constant space overhead, requiring no dynamic allocation. Our implementation is relatively fast, especially due to the `byteset` addition to the algorithm, which speeds up many no-match cases. A bad case for the two way algorithm is: ``` let haystack = (0..10_000).map(|_| "dac").collect::<String>(); let needle = (0..100).map(|_| "bac").collect::<String>()); ``` For this particular case, two way is not much faster than the naive implementation it replaces. |
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| .. | ||
| bit | ||
| btree | ||
| bench.rs | ||
| binary_heap.rs | ||
| enum_set.rs | ||
| fmt.rs | ||
| lib.rs | ||
| linked_list.rs | ||
| slice.rs | ||
| str.rs | ||
| string.rs | ||
| vec_deque.rs | ||
| vec_map.rs | ||
| vec.rs | ||