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OpenCL

arsenm
Adept III

SDK 2.6 issues/questions

Does the Multi-GPU work with Xinerama enabled now? I had multiple GPUs working in Linux before, but only if Xinerama wasn't enabled.

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nou
Exemplar

SDK 2.6 issues/questions

don't enable Xinerama. it is deprectated old way to create one multidisplay. use xrandr that is now supported way.

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Meteorhead
Challenger

SDK 2.6 issues/questions

I know about DISPLAY and COMPUTE (more up to date) variables, however they do not work. I have used multi-GPU before on SLC and it worked fine, it is only now that it doesn't work. Everything that worked under Ubuntu worked on SLC too, no changes required.

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anatolix
Journeyman III

SDK 2.6 issues/questions

Can I develop with AMD APP SDK with Visual Studio Express, or I need full Visual Studio?

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nou
Exemplar

SDK 2.6 issues/questions

yes you can. but AFAIK you can't use profiler with EE as it doesn't have plugin support. but there should be a command line version of profiler so you can try use that.

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Dr_Haribo
Journeyman III

SDK 2.6 issues/questions

Does anyone know what the new cl_amd_media_ops2 extension provides?

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nou
Exemplar

SDK 2.6 issues/questions

little dig up in libamdocl64.so brings this

amd_msad
amd_sadw
amd_sadd
amd_qsad
amd_mqsad
amd_bfm
amd_bfe
amd_median3
amd_min3
amd_max3

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gat3way
Journeyman III

SDK 2.6 issues/questions

Those...

 

amd_msad

amd_sadw

amd_sadd

amd_qsad

amd_mqsad

amd_bfm

amd_bfe

amd_median3

amd_min3

amd_max3



 

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jross
Adept I

SDK 2.6 issues/questions

I haven't received any replies questions on multi-GPU in this thread:
http://forums.amd.com/devforum/messageview.cfm?catid=390&threadid=157728

I wanted to follow up in this thread.

Using the following system configuration:
CentOS 6.0 64-bit
Catalyst 11.12
AMD APP SDK 2.6
Two Radeon HD 6970s
Environment variables: COMPUTE=:0 and DISPLAY=:0

I am able to run codes with single context, multiple GPUs (2x6970), but the runtime appears to serialize the kernel execution with Catalyst 11.12 + SDK 2.6.  Codes take twice as long to execute as they should, however, they do produce the expected result.  This did not occur with the 11.4 driver + 2.4 runtime in most cases.

AMD had multi-GPU kernel execution serialization in Catalyst up until 10.4 (yes, 2010) when they fixed it.  The drivers then worked properly, with respect to multi-GPU kernel execution, for the next year until Catalyst 11.4.  Now we're getting pretty close to a year without a proper driver.  The GCN "Tahiti" architecture is very much compute-oriented and there's little incentive for anyone to put more than one of these in a system if they're too much of a challenge to develop.  It's not like developers can fall back to an older version of Catalyst with the new uarch.

To utilize multiple GPUs with Catalyst 11.12 + SDK 2.6 + Linux, one must create X OpenCL contexts, each addressing one unique GPU device, where X is the number of GPUs in your system.  This is counter to the premise of the OpenCL specification but the separate contexts/devices may then execute kernel code in parallel.

I haven't had serious trouble booting with multiple GPUs in RedHat-based Linux for some time.  I recommend booting to the command line (runlevel 3) to install drivers.  After installing drivers, run "aticonfig --adapter=all --initial -f".  Reboot just to be safe.  I've never had to play with Xinerama or xrandr.

If anyone does find the magic formula for proper asynchronous kernel execution in Catalyst >=11.12 + SDK 2.6 + Linux + single-context + multi-GPU, please let everyone know.

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antzrhere
Adept III

SDK 2.6 issues/questions

Enabling the cl_khr_gl_sharing flag still comes up with an error:

error: can't enable all OpenCL extensions or unrecognized OpenCL extension
  #pragma OPENCL EXTENSION cl_khr_gl_sharing : enable

...OpenGL sharing does still work though (as always) and give the expected results, but can't understand why enabling this extension still brings up an error  (on my system atleast) as I reported it a while back.

Win 7 64bit professional, ATI 5870, SDK 2.6, Catalyst 11.12

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