[ruby-core:96668] [Ruby master Feature#16468] Switch to Miller-Rabin for Prime.prime?
From:
mame@...
Date:
2020-01-05 01:41:09 UTC
List:
ruby-core #96668
Issue #16468 has been updated by mame (Yusuke Endoh).
It can fall back to APR-CL primality test when Miller-Rabin does not work. In my personal opinion, it would be best to keep prime.rb simple because it is a hobby library.
You may be interested in my gem: https://github.com/mame/faster_prime
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Feature #16468: Switch to Miller-Rabin for Prime.prime?
https://bugs.ruby-lang.org/issues/16468#change-83650
* Author: steveb3210 (Stephen Blackstone)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
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The miller-rabin algorithm is a non-deterministic primality test, however it is known that below 2**64, you can always get a deterministic answer by only checking a=[2,3,5,7,11,13,17,19,23, 29, 31, 37]
Given that Prime.prime? would never respond in a reasonable amount of time for larger numbers, we can gain much more utility and performance by switching..
```
user system total real
miller_rabin: random set 0.150000 0.000000 0.150000 ( 0.152212)
Prime.prime?: random set 0.270000 0.000000 0.270000 ( 0.281257)
user system total real
miller_rabin: 16 digits 0.010000 0.000000 0.010000 ( 0.000300)
Prime.prime? 16 digits 2.200000 0.020000 2.220000 ( 2.368247)
user system total real
miller_rabin: 2-10000 0.030000 0.000000 0.030000 ( 0.035752)
Prime.prime? 2-10000 0.020000 0.000000 0.020000 ( 0.022948)
---Files--------------------------------
patch.diff (1.75 KB)
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