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Old 2010-12-10, 00:09   #22
Oddball's Avatar
May 2010

499 Posts

Originally Posted by Ken_g6 View Post
Speaking of that post, here's a quick summary of the arguments for both sides:

Pro-LLR GPU side:
1.) Allows people with GPUs freedom of choice. If an GPU program for LLR is developed, those with GPUs can choose to either sieve or test for primes.
2.) Allows for faster verification of large (>1 million digit) primes.
3.) GPU clients are not optimized yet, so there's more potential for improvement.
4.) GPUs are more energy efficient than old CPUs (Pentium 4's, Athlons, etc), judging by the amount of electricity needed to LLR one k/n pair.

Anti-LLR GPU side:
1.) Reduces the number of participants. Those without fast CPUs would be discouraged from participating since they would no longer be able to do a significant amount of "meaningful" LLR work (defined as LLR work that has a reasonable chance of getting into the top 5000 list).
2.) GPUs are much less effective at primality testing than at sieving or trial factoring. Computing systems should be used for what they are best at, so CPU users should stick to LLR tests and GPU users should stick to sieving and factoring.
3.) GPUs have a high power consumption (~400 watts for a GPU system vs. ~150 watts for a CPU system). Even when comparing power needed per primality test, they are less efficient than core i7's and other recent CPUs.
4.) GPUs have a higher error rate than CPUs. It's much easier to check factors than it is to check LLR residues, so GPUs should stay with doing trial division.
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