GPU_ECM seems to not use GPU

[Gordon]

I managed to find and download an apparently gpu enabled version, found the missing nvivia dll and tried it out with a prime95 stage 1 curve.

Result? - it did ALL of the calculation on the cpu, didn't touch either gtx card once, even specifiying -gpudevice 0 made no difference at all...and it's about 25% slower than gmp-ecm v7...oh well

[wombatman]

GPU-ECM uses the CPU for stage 2. It uses the gpu (with flag -gpu) for stage 1 only. The GPU-enabled stage 1 is also limited to numbers less than or equal to 2^1018-1 for the time being.

[Gordon]

Originally Posted by wombatman

GPU-ECM uses the CPU for stage 2. It uses the gpu (with flag -gpu) for stage 1 only. The GPU-enabled stage 1 is also limited to numbers less than or equal to 2^1018-1 for the time being.

So, as everything below M1019 has been factored, there isn't in fact any use for gpu_ecm?

[wombatman]

For Mersenne, no. For other numbers, it works brilliantly.

[MatWur-S530113]

Originally Posted by Gordon

So, as everything below M1019 has been factored, there isn't in fact any use for gpu_ecm?

in addition to wombatman's answer:
the following exponents of M-numbers with already known factors have composite cofactors with 1018 or less bits (atm, of course):
1213, 1217, 1229, 1237, 1297

see f.e. factordb.com .

but I don't think it's worth to run stages 1 with the gpu on them with B1 less than 1e9