ECM for CUDA GPUs in latest GMP-ECM ?

[EdH]

Originally Posted by SethTro

I'm happy to look at this as a bug. I vaguely remember that I wasn't sure if I should always stop or only if the cofactor is composite.

Thanks, but I've moved to using a separate machine with ecm.py and it is working as needed.

I'd leave as is unless others are interested. For me it is no longer an issue.

Again, thank you for considering it.

[storm5510]

There seems to be an oddity about using a GPU in GMP-ECM.

The --help switch shows the maximum size of a B1 value is 2^1018. Using Windows Calculator to calculate log(2) * 1018 says this is a 308 digit value.

If I run this:

echo "2^14447-1" | gpuecm -gpu -maxmem 2048 5e6 10e6

I get this message:

GMP-ECM 7.0.4-dev [configured with MPIR 2.7.2, --enable-gpu, --enable-openmp] [ECM]
Input number is 2^14447-1 (4349 digits)
GPU: Error, input number should be strictly lower than 2^1018
please report internal errors at <ecm-discuss@lists.gforge.inria.fr>.

B1 in my example is 5e6 or 5,000,000. This is obviously smaller than a 308 digit number.

I am missing something here and I cannot determine what it is.

[paulunderwood]

Originally Posted by storm5510

There seems to be an oddity about using a GPU in GMP-ECM.

The --help switch shows the maximum size of a B1 value is 2^1018. Using Windows Calculator to calculate log(2) * 1018 says this is a 308 digit value.

If I run this:

echo "2^14447-1" | gpuecm -gpu -maxmem 2048 5e6 10e6

I get this message:

B1 in my example is 5e6 or 5,000,000. This is obviously smaller than a 308 digit number.

I am missing something here and I cannot determine what it is.

You are missing something. The inputted number is too big. You specified 2^14447-1. The max is 2^1018.

[SethTro]

If you are willing to compile gmp-ecm from source you can test larger input numbers (it's also faster).

See https://www.mersenneforum.org/showthread.php?t=27103

[storm5510]

Originally Posted by paulunderwood

You are missing something. The inputted number is too big. You specified 2^14447-1. The max is 2^1018.

Understood. IMHO, it is not good for much of anything at this size.