Matching iMacs different cuda task speeds


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Message boards : Number crunching : Matching iMacs different cuda task speeds

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Dan Stoneham
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Message 1331591 - Posted: 26 Jan 2013, 15:53:03 UTC

Hi all,

I am running Seti with Lunatics app on 2 iMac's (late 2012) that are both currently using windows 7 x64 via boot camp.

They are identical with the exception of 1 has a 3.2Ghz i5 and the other a 3.4Ghz i7. Both have 16GB of RAM and a GTX 680MX GPU but when I am running the Cuda tasks I have noticed the i5 machine can complete a task in ~2min 40s whereas the i7 machine is taking ~6min 30s.

Anybody any ideas on this? The computing preferences are also identical. The i5 has 4 cores no HT whereas the i7 has 4 cores with HT, not sure if this will affect it, but being GPU tasks I didn't think this would make any difference.

Thanks,

Dan

Tom*
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Message 1331593 - Posted: 26 Jan 2013, 15:59:49 UTC - in response to Message 1331591.
Last modified: 26 Jan 2013, 16:02:13 UTC

First test I would do is turn off HT on the i7 and see if it makes any difference.

Doubt many of us have been to that kind of boot camp:-)

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Message 1331596 - Posted: 26 Jan 2013, 16:09:36 UTC

Are the GPU's identical?

I'm assuming you are testing on the same W/U.

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ClaggyProject donor
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Message 1331597 - Posted: 26 Jan 2013, 16:15:33 UTC - in response to Message 1331591.
Last modified: 26 Jan 2013, 16:23:01 UTC

You're only got two hosts on your Account, One running Windows 7 Professional x64, the other running Darwin 12.2.1, so i can't compare GPU tasks from one host to the other:

Computers belonging to Dan Stoneham

Not all MB tasks are of the same length, how long they take depends on the Angle Range,

Very High Angle Range tasks where the telescope is being swept across the sky take the shortest time to complete, about 2 minutes on my GTX460,
Normal AR (~ 0.44 AR) tasks where the telescope is static, but the earth rotates, take about 8 minutes on my GTX460,
Very Low Angle Range tasks where the telescope is pointed at a fixed point in space, take something like an hour or two to do, because of this they aren't sent to GPUs,
you can also get tasks that have an AR of 0.37 that take an extra minutes or two, and tasks outside the defination of VLAR that take extra time too,

Claggy

Dan Stoneham
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Message 1331959 - Posted: 27 Jan 2013, 12:06:16 UTC

Thanks for your replies,

Newbie mistake, I thought each W/U was the same size, I hadn't realised there were different types :)

The GPU's are identical (GTX 680MX)

The 2 iMacs are on 2 different accounts but part of the same team. The 2 you see on my account (1 Windows, 1 Darwin) are actually the same machine just booted into different OS's.

Thanks,

Dan

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Message 1332205 - Posted: 28 Jan 2013, 11:34:27 UTC - in response to Message 1331593.

You can keep HT enabled on i7 and limit the CPU to use 50% of processors. This way you have maximum number of CPU-FP units utilized and those extra HT cycles (cores) are reserved for GPU tasks requiring CPU for memory transfer/logic.


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Message boards : Number crunching : Matching iMacs different cuda task speeds

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