[PATCH] D51689: [clangd] Dense posting lists proof-of-concept
Sam McCall via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Wed Sep 5 09:31:33 PDT 2018
sammccall created this revision.
sammccall added a reviewer: kbobyrev.
Herald added subscribers: cfe-commits, kadircet, arphaman, jkorous, MaskRay, ioeric, ilya-biryukov.
This uses a bitmap representation instead of a list if the density of
the list is high enough (at least 1 in 32, which is the breakeven point
sizewise).
Experimenting with the LLVM index, this saves about 3% of total posting
list size, which isn't worth the complexity.
However it should also improve iterator performance somewhat:
- advance is within a constant factor (find next set bit, average step is bounded)
- advanceTo is constant time instead of log(n) with random accesses
If the posting lists that are dense are also commonly used in queries
(seems likely for common trigrams) then this may be worth doing for
latency reasons.
I'm uploading this so Kirill can experiment with benchmarks.
Repository:
rCTE Clang Tools Extra
https://reviews.llvm.org/D51689
Files:
clangd/index/dex/DexIndex.cpp
clangd/index/dex/Iterator.cpp
clangd/index/dex/Iterator.h
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