Speed up multimodular algorithm in bad case #39204
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Documentation preview for this PR (built with commit 6eeb258; changes) is ready! 🎉 |
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Superseded by #39733 |
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Edit: Now flint has fixed flintlib/flint#2129 , it should be better to just switch to flint entirely — according to flintlib/flint#2129 (comment) , one of the possible algorithms by flint is multimodular, which should be faster than or equal to what we're having now. If it is slower in any case, bug can be reported upstream.
Related to #39197.
Technically the algorithm doesn't deviate from @williamstein 's original book; however the original book doesn't say how many additional primes to add each time.
The original implementation roughly consider 3 more primes each time. This can be highly inefficient when there are more columns than rows, which makes the result's height much higher than the guess.
This increases the length of
Mby roughly a factor of1.2each time. Worst case it makes the algorithm slower by a (hopefully small) constant factor.For the added test case, it appears to improve the performance. (Originally takes 40s, now takes <10s on my machine)
📝 Checklist
⌛ Dependencies