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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