cgen,rand,hash: new wyhash v4.2#25907
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Do I need to create my own separate PR in |
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Preferably yes - some of the tests there are brittle and depend on the versions of the exact hash and pseudo random generators used by default :-| . |
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Can you please also run: The slowdown may be (hopefully) just for the version compiled with tcc. |
spytheman
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Dec 6, 2025
spytheman
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spytheman
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Dec 6, 2025
| const count = 2000 | ||
| // Accepted error is within 5% of the actual values. | ||
| const error = 0.05 | ||
| const error = 0.06 |
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Why is that increased?
If that is indeed needed, please also update the comment above it.
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Intuitively, I would have expected that the deviations, would have been ~ the same, as long as the pseudo random generator was ~ of the same quality 🤔 .
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With 0.5 it fails this way. Almost equal:
vlib/rand/dist_test.v:127: ✗ fn test_exponential
> assert math.abs((f64(var / 2000) - variance) / variance) < f64(2 * 0.05)
Left value (len: 19):
`0.10262020251738975`
Right value (len: 3):
`0.1`
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I think it is better to modify just this assertion, if the rest fit within the const error = 0.05 margin.
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perhaps only tweak the 2 coefficient locally?
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I spent these hours finding a new beautiful seed value at which the test passes at the old error threshold of 5%. What you think?
diff --git a/vlib/rand/dist_test.v b/vlib/rand/dist_test.v
index 17081a97d..e4893280b 100644
--- a/vlib/rand/dist_test.v
+++ b/vlib/rand/dist_test.v
@@ -4,9 +4,9 @@ import rand
// The sample size to be used
const count = 2000
// Accepted error is within 5% of the actual values.
-const error = 0.06
+const error = 0.05
// The seeds used (for reproducible testing)
-const seeds = [[u32(0xffff24), 0xabcd], [u32(0x141024), 0x42851],
+const seeds = [[u32(0x24ffff), 0xabcd], [u32(0x141024), 0x42851],
[u32(0x1452), 0x90cd]]
fn test_bernoulli() {
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Let me know if you accept |
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I do in general. It is better to stick to the latest version of the hash. The PRs to vls and vsl, will be needed so that they could be merged and tested right before merging this one. I want to minimize the time window, during the CI for other unrelated PRs here could potentially break, and thus when they will need to be rebased. |
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Thank you @tankf33der 🙇🏻 . |
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…eeds were found by @tankf33er in #25907)
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…eeds were found by @tankf33er in vlang#25907)
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My attempt to update
wyhashto version 4.2I double-checked everything byte by byte and line by line by eye.
When I myself tried to check the current
wyhashfrom the author's repo, it immediately caught my eye that the current version is not in the list of official old versions - I consider it the main disadvantage.Updated all affected tests that involve
wyhash, added all official test vectors.If you look closely at the diff, you can see that not only the magic values were updated, but also the work with them. This slowdown (disadvantage of version 4.2 compared to the current implementation) is visible in the operation of
compare_pr_to_master.vwhich I attach below (from my slow-cheap laptop).Tested the new Random Number Generator using the
PracRandtool, ran up to and including 4TB without obvious defects.