Hi Andreas,
thanks for the answer.
You are right: the PC is not friezed: CPU is free to work I tested it
playing a video in background: the display is friezed but audio
continue to work correctly.
As you say, this behaviour is independent from the hardware: I have
tried also with NVIDIA hardware and using two 4870 single and in
crossfire. Now way: the video always freeze.
Windows and OSX have the same issue?
Regarding the memory report, I have noticed that NVIDIA OpenCL
implementation fills all the fields and the reports are correct. But
NVIDIA implementation does not support CPU, so I will stay with
AMD/ATI. Red pill, no questions :-).
Finally, regarding the 3Gbyte limit on x86(CPU) OpenCL, I suppose that
the actual version of OpenCL is a pure 32 bit (4Gbyte) application and
the 3GByte mirror the 32 bit Linux/Windows barrier.
Thanks a lot for your answer and for your code: pycuda and pyopencl
are a lot more fun to use than pure C/C++ development.
Regards
Simone Mannori
www.scicos.org ; www.scicoslab.org
On 5 November 2010 20:26, Andreas Kloeckner <[email protected]> wrote:
> Hi Simone,
>
> On Fri, 5 Nov 2010 09:15:33 +0100, Simone Mannori <[email protected]>
> wrote:
>> I have successfully installed pyopencl on a i7 laptop with a Mobile
>> 5850 ATI video card.
>> My software configuration is:
>> - Ubuntu 9.10 64 bit
>> - Stream 2.2 (AMD/ATI)
>> - latest AMD/ATI mobile video driver (10.10)
>>
>> Playing with the various demos included in pyopencl :
>> 1./ if the code runs on the CPU (using OpenCL) all the 8 "cores" of
>> the i7 goes to 100% , but the machine is still usable; mouse react and
>> the other windows are active;
>> 2./ if the same code run on the GPU (using OpenCL) the machine
>> "freeze" completely during the execution of the kernel.
>>
>> N.B: "freeze" means that the PC does not react during kernel execution
>> but, at the end, my laptop correctly restart normal operation: no
>> stability problem, sudden crash or memory leaks. Numerical results are
>> ok in both cases. I suspect that is not a stability related issue but
>> only how "wait" is implemented (probably there is a "busy wait" inside
>> the GPU code).
>>
>> My "newbie" questions are:
>> - situation 2./ is it normal? Can I avoid the "freeze" of the machine ?
>
> I don't think the machine *actually* freezes--it's just that while the
> GPU is busy computing, your display will not update. (Which I find
> understandable.) Try running a (CPU) program in parallel to your
> computation and see if it makes progress while your GPU is active. I'd
> bet it does.
>
> This behavior is actually the same on Nvidia GPUs. The only recipe
> against that is to only submit compute kernels that finish in ~10 ms or
> less, making the interruptions bearable. The mouse movement still feels
> a bit jittery, but not so severe as to make the machine unusable.
>
>> - can I use CPU _and_ GPU at the same time? How do that from pyopencl ?
>
> You just create a context on each and go to town.
>
>> Another observation is about the amount of available memory reported:
>> - pyopencl reports 3Gbytes for the CPU and 512Mbytes for the GPU, but
>> I have 6Gbyte of RAM and 1Gbyte of video RAM ....
>
> That seems implementation-dependent, and not likely the fault of
> PyOpenCL. For my Nvidia card, I get the full ~1GB. For the AMD CPU CL
> implementation, I get 3 out of six GBytes like you. Not sure what's
> going on.
>
> Andreas
>
>
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