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Re: [Fsuk-manchester] Open ARM GPU drivers


From: Bob Ham
Subject: Re: [Fsuk-manchester] Open ARM GPU drivers
Date: Thu, 07 Feb 2013 09:44:23 +0000
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On Tue, 05 Feb 2013 17:42:02 +0000, Dave Love <address@hidden> wrote:
> Bob Ham <address@hidden> writes:
> 
>>> If so, what
>>> sort of performance might Mali 400, for instance, provide?
>>
>> Good question.  I can't imagine you'd get anywhere near the kind of
>> performance of a desktop graphics chip due to the power constraints.
> 
> Yes, but the comparison wouldn't be with other GPUs, but with SIMD
> (SSE-type) units.

I'm confused by this I must say.  I thought GPUs *were* SIMD units.  In
fact, looking at Wikipedia, it explictly lists GPUs as an example of SIMD
architecture:

  http://en.wikipedia.org/wiki/Flynn%27s_taxonomy


>> I'm not surprised; the focus of most efforts are intended to support
>> things like simulations, computational biology and other scientific
>> computing, often in supercomputers.
> 
> [That's what I do, for some value of "supercomputers".]

Cool.  You'll have to excuse me then for trying to "teach your grandmother
how to suck eggs", as it were :-)


>> In that kind of context it doesn't make much sense to target low
>> power, performance-constrained chips like the Mali.
> 
> It might, if you have them anyway in a well-ARMed system intended for
> specific sorts of jobs, even if you wouldn't use them for HPC.

It may do, yes, and looking at the power consumption numbers for the
Epiphany processors, I can imagine that there may be much more interest in
future.

Really though the point I was making, and please correct me if I'm wrong,
was that in HPC the general focus is on high-powered processors like
Xeon/Opteron CPUs and ATI/NVIDIA GPUs.  For example, Titan has Opteron CPUs
and Tesla GPUs, Tianhe-1A has Xeon CPUs and Tesla GPUs upgraded from Xeon
CPUs and Radeon GPUs, and our own HECToR has Opteron CPUs.


>> (Unless, of course, you're able to engineer your own floating-point
>> applications directly for the hardware.
> 
> The appeal of OpenCL is in avoiding some level of hardware specifics
> generally, though you typically do have to write hardware-specific
> assembler to get performance in the kernels :-(.

Hmm.. that is disappointing.  It does kind of defeat the purpose of OpenCL
:-/

-- 
Bob Ham <address@hidden>

for (;;) { ++pancakes; }



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