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Message 20972 - Posted: 11 Aug 2015, 15:08:29 UTC

Are there plans for a sieve app for Intel GPUs?

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Message 20976 - Posted: 11 Aug 2015, 20:19:11 UTC - in response to Message 20972.

Are there plans for a sieve app for Intel GPUs?


The short answer is Yes.

The current sieve app uses a sieve for 2^32 numbers which results in about 40 million numbers to be checked for every 2^32 in the workunit. It splits that into 4 so it calculates the steps for about 10 million numbers per kernel. That works fine on new AMD GPUs but some older ones and some nVidia GPUs crash with that many numbers per kernel since it takes more than 33 milliseconds to check them. So.... I'm testing a new sieve version where the default will be to use a 2^26 sieve which needs 1 million numbers checked per every 2^26 and results in 250K items per kernel. But, the sieve size can be controlled kin the collatz config so those with GPUs that can handle the larger sieves (2^27 thru 2^32) can choose that size.

For example, using lut_size=12, sieve_size=20, kernels_per_reduction=4 results in almost no CPU used but only puts a load of about 30% on the GPU. Using lut_size=15, sieve_size=28, kernels_per_reduction=48 results in high CPU but runs at a 99% GPU load on my laptop but with good video response.

If I don't find any issues in my testing in the next several days, I plan on rolling out platform by platform as I finish testing each. Since my laptop has both an Intel and an nVidia GPU, those will likely be the first two apps released.

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Message 20992 - Posted: 13 Aug 2015, 16:46:07 UTC

v1.07 of the sieve app has been released for AMD, nVidia, and Intel GPUs.


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