[Octave-bug-tracker] [bug #61312] Extending isprime() with Miller-Rabin test

[Arun Giridhar]

Follow-up Comment #20, bug #61312 (project octave):

@Markus: Thank you for the tip about boolNDArray. I was able to get it to work
with that change. Earlier I had been trying to construct an octave value
vector directly instead of converting a boolNDArray with ovl().

I'm also very surprised at exactly how much overhead was present in that last
for-loop. Moving that to C++ sped up the overall performance by 2.5x from that
change alone. The latest patch (Patch 12, attached to this comment) is
therefore 2.5x as fast as Patch 11 in Comment #16. Thank you for the guidance
to look at that part.

Patch 12 attached with the following changes compared to Patch 11:

1. Moved the final for-loop in isprime.m to C++, enabling a vector to be
passed instead of a sequence of scalars.

2. Renamed internal functions in the Miller-Rabin code and made some
documentation edits for the end user.

3. Since Miller-Rabin was now faster than before, the THRESHOLD value needed
to be retuned in isprime.m.

Please examine the last line of isprime() and the corresponding C++ use of
boolNDArray in __isprimelarge__. Is there a performance penalty to boolNDArray
when the Octave function will always call it with a row vector?

(file #52166)
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Additional Item Attachment:

File name: patch12.patch                  Size:13 KB
    <https://file.savannah.gnu.org/file/patch12.patch?file_id=52166>



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