kc3-lang/libxkbcommon

2021-03-29T16:05:14

compose: use a ternary tree instead of a regular trie Previously we used a simple trie with a linked list for each chain. Unfortunately most compose files have very long chains which means the constructions performs an almost quadratic number of comparisons. Switch to using a ternary search tree instead. This is very similar to a trie, only the linked list is essentially replaced with a binary tree. On the en_US/Compose file, the perf diff is the following (the modified function is `parse`): Event 'cycles:u' Baseline Delta Abs Shared Object Symbol ........ ......... ................ ................................. 39.91% -17.62% bench-compose [.] parse.constprop.0 20.54% +6.47% bench-compose [.] lex 17.28% +5.55% libc-2.33.so [.] __strcmp_avx2 12.78% +4.01% bench-compose [.] xkb_keysym_from_name 2.30% +0.83% libc-2.33.so [.] __GI_____strtoull_l_internal 3.36% +0.78% bench-compose [.] strcmp@plt Thanks to some careful packing, the memory usage is pretty much the same. Signed-off-by: Ran Benita <ran@unusedvar.com>