Is it a good idea to have PPS Sv as CPU default subproject? Feels to me it's a big waste of CPU cycles, they take almost a day while a GPU takes a few minutes.
SGS would be a good choice, in my opinion. The tasks are short, so new users won't be freaked out. And they run efficiently on CPU, i.e. the user is actually doing useful work.
Primes: 1281979 & 12+8+1979 & 1+2+8+1+9+7+9 & 1^2+2^2+8^2+1^2+9^2+7^2+9^2 & 12*8+19*79 & 12^8-1979 & 1281979 + 4 (cousin prime)