Author :
Ran Benita
Date :
2021-03-29 16:05:14
Hash :02b9cabf Message :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>
Ran Benita