I checked continuously from 2

^{64} but I'm only doing 1 Fermat test so it is possible that a number is incorrectly called a prime. I think it is unlikely that this has lead to missing a large gap (very unlikely if the math in this post is correct

https://mersenneforum.org/showpost.p...8&postcount=20) but it is still possible. The easiest way for me to fix this issue would be to use 12 SPRP tests which is sufficient to prove primality. Half the remaining numbers are prime after sieving so the code would take about 6-7 times longer to run. It's possible it would be faster to check with sieving only. It would require sieving up to primes a little above 2

^{32}.

This is also new GPU code so it is possible that there is some other error. I did find all the gaps above 1000 that ATH found so there is some confidence that it is working correctly.