Hi James, thanks for your questions! and sorry if sometimes GPU crashes your system!

GPU v0.64c has to function that do the power modulo a number:

"2,3,9,powmod" is the old one and is implemented in the plugin basic.dll . For checking if the discrete logarithm is exact, I normally use the faster "2,3,9,squareandmul" that uses the Square and Multiply algorithm for fast factorisation. This one is implemented in the plugin crypto.dll
Refer to both cryptodll.pas and basicdll.pas in the source code for see how they are implemented.

I know from your other post that you are implementing a Gnutella client in C, it should be possible to write plugins in C, if you respect the methods signature which is a pointer to a struct that contains an array of floating numbers and an integer used for the stack pointer.

See chapter 9 of the documentation, perhaps you could try to implement your own plugin with a gcd() method.

I know about the two errors, the exception of 10001 should be catched, but I don't treat them correctly.

and of course if you want to help in some way, I would be very happy to welcome you in our development team.