perf: pre-allocate buffers with with_capacity()
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allocating the buffer prior prevents a lot of reallocations from regrowing
in profiling, the macro option had a lot of overhead vs `with_capacity()`
RoloEdits
commented
Oct 7, 2023
| let mut buf = Vec::new(); | ||
| let mut val_buf = Vec::new(); | ||
| let mut buf = Vec::with_capacity(1024); | ||
| let mut val_buf = Vec::with_capacity(1024); |
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val_buf in particular had the biggest impact when profiling with this change
|
Marginal improvement but still an improvement: pre post: |
|
Awesome, thanks! |
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Pre-allocating removes a lot of regrows for the buffers.
Benchmarks
Quick benchmark opening a 150k row, 17 column
.xlsxfile shows 15% increase in performance.master:perf/pre_alloc_buf:Profiles
Purple highlight is
alloc.Current
master:Change:
Changed from
vec![]macro towith_capacity()as there was an introduction to a lot of instructions running.vec![0;N]:with_capacity(N):