perf: better cast create2 #6212
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mattsse
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Nov 3, 2023
crates/cast/bin/cmd/create2.rs
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| let salt_word = unsafe { &mut *salt.0.as_mut_ptr().cast::<usize>() }; | ||
| *salt_word = start; |
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not obvious what's going on here, this sets the salt's first word to the thread's index incrementing it by the number of threads, so the salt cycles through all unique values?
needs docs+SAFETY
salt uses u64 internally? should this cast to u64? read b256 aligned wrong, or maybe not idk
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n_threads=4
- (thread)i=0: word=0; word=4; word=8
- (thread)i=1: word=1; word=5; word=9
- (thread)i=2: word=2; word=6; word=10
- (thread)i=3: word=3; word=7; word=11
Evalir
approved these changes
Nov 3, 2023
|
Added |
mattsse
reviewed
Nov 3, 2023
| let salt_word = unsafe { &mut *salt.0.as_mut_ptr().cast::<usize>() }; | ||
| *salt_word = start; | ||
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| // Important: set the salt to the start value, otherwise all threads loop over the |
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the loop only covers u64 or u32 depending on the arch, so not all the available 32bytes?
fine?
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>> u32::MAX / 128
33554431
>> u64::MAX / 128
144115188075855871
iterations needed to overflow, I don't think that's reachable
mattsse
approved these changes
Nov 3, 2023
Evalir
approved these changes
Nov 3, 2023
This was referenced Apr 26, 2024
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Motivation
Speed
Solution
Make faster