Saturday, July 11, 2020

Rev it up

Under the direction of Mark "rogue" Rodenkirch in mersenneforum, on June 28 I was able to run a probable-prime search/verification program that executes some six times faster than what I can do in Mathematica. Considering that Mathematica is what I have been using for my large-Leyland-prime search for almost five years now, that's an awful lot of wasted time!

In order to more efficiently use this program (OpenPFGW; OS X version, pfgw64), a prime-sieving algorithm (OS X version, xyyxsieve) was recommended as a precursor, in order to trim the available candidate numbers to a much-lesser amount. In Mathematica such a routine is incorporated in its PrimeQ function but PrimeQ will not go beyond its built-in limit. So, on July 2 I ran my first prime sieve.

This is a game changer for me. On Wednesday afternoon, a storm knocked out the power here for longer than I had computer battery-backup.


As a result, my Leyland prime search for interval #9 was interrupted. It was scheduled for completion July 25 but recent experience suggested that it would not actually have finished until a week into August. So I used the heavenly portent to convert my remaining search-space into a format that I could use for xyyxsieve and, subsequently, pfgw64. A lot of ongoing manual fiddling and such was needed for the conversions but this allowed me to get used to the new processes. This morning it completed the searches!

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