HeaderMap: Store pos and hash as u16#386
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seanmonstar merged 3 commits intohyperium:masterfrom Jan 27, 2020
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Oh sweet! (I've filed #387 for the deprecation errors.) |
HeaderMap currently truncates all hashes to 16 bits, and limits its capacity to 32768 elements. The comments say this is done in order to store positions and hashes as u16, to improve cache locality. However, they are currently stored as usize. This patch changes the code to match the comments. This does not appear to cause any measurable improvement or regression in speed in the HeaderMap benchmarks. However, it should at least reduce the memory footprint of every Headermap.
The actual maximum capacity is 24578 (i.e. `32768 * 3/4`). A higher number would cause the raw capacity (i.e. `capacity + capacity/3` rounded to the next power of 2) to overflow `u16`.
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Note that the I didn't change |
seanmonstar
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Jan 27, 2020
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HeaderMap currently truncates all hashes to 16 bits, and limits its
capacity to 32768 elements. The comments say this is done in order to store
positions and hashes as
u16, to improve cache locality. However, they arecurrently stored as
usize. This branch changes the code to match thecomments.
This does not appear to cause any measurable improvement or regression in
speed in the HeaderMap benchmarks on my workstation. However, it should at
least reduce the memory footprint of every Headermap.