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Problem:Fortran code with open ACC doesn't gain any speed up
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rzou1



Joined: 03 Feb 2014
Posts: 5

PostPosted: Thu Feb 06, 2014 6:50 pm    Post subject: updates Reply with quote

Hi Mat,
I tried the "-ta=tesla:time", but it still doesn't produce speed up for the case. I tried to profile as you adviced, but got an error that the "libaccprof.dll" not found. I copied the .dll to the folder where I have the executable, but still doesn't work.
I then turned to test the AccelPM_Matmul case you suggested. For this case, I compiled with the following options:
1) no ACC
2) enable ACC, but no target accelerator
3) enable ACC and target accelerator to NVIDIA Tesla

Also, I set the size to 2048 (from 1024) to make the problem large enough. The time took for 1) is about 8 second, and for both 2) and 3) are 6.2 second, which show about 30% speedup. However, when run the executable with 2) and 3), I frequently encounter the problem: cudastreamsynchronize returned error 702: launch timeout

And when this error occur, the display of the computer blank out, with the message:"Display driver stop working...". I wonder does this always happen when use GPU to do the computation? is there anyway to avoid this problem?

This problem occur about 50% of the time when the size of the problem is 2048, but when I increase the size to 3072, it occur 100% of the time.

Thanks very much!
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mkcolg



Joined: 30 Jun 2004
Posts: 5952
Location: The Portland Group Inc.

PostPosted: Fri Feb 07, 2014 3:59 pm    Post subject: Reply with quote

The Windows display driver model (WDDM) will time out all but the shortest of jobs. Your options are to increase the timeout value (in the registry) or, since you have a Quadro, use the nvdia-smi utility to switch to Tesla Compute Cluster (TCC) mode.

- Mat
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rzou1



Joined: 03 Feb 2014
Posts: 5

PostPosted: Tue Feb 11, 2014 8:52 pm    Post subject: Reply with quote

thanks Matt. I tried to made the computation task more intensive, then I can see the speed up of the ACC.
BTW, I have got a question about the accelerator profiling. I noticed that the code that I compiled with the PGI fortran doesn't show consistent behavoir regarding the accelerator profiling, i.e., sometimes it can generate accelerator profiling information, but sometimes it just generate nothing about the accelerator's performance.
I used the Visual Fortran IDE, and specify the accelerator profiling at the "Perperties-->Debug-->accelerator profiling (yes)

truely appreciate your help.
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mkcolg



Joined: 30 Jun 2004
Posts: 5952
Location: The Portland Group Inc.

PostPosted: Wed Feb 12, 2014 9:39 am    Post subject: Reply with quote

Quote:
i.e., sometimes it can generate accelerator profiling information, but sometimes it just generate nothing about the accelerator's performance.
Is there anything different between when the profile is printed versus when it's not? It's odd behavior that I don't have an answer for.

"Properties-->Debug-->accelerator profiling" sets the environment variable PGI_ACC_TIME=1. So it could be not getting set in some cases, though I don't know why. Another possibility is that it's not running on GPU (by default a unified binary is created which will create a host and GPU version of the code, i.e. -ta=host,tesla). Finally, maybe the output is getting lost somehow?

Some things to try are setting "-ta=tesla:time" (so profiling is always on). This will also remove the host version.

- Mat
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