Re: [atlas-devel] About ATLAS and ARM Cortex-A9 Exynos 4412 theoretical performance for DGEMM

[Tom W. <tom...@ve...>]

Well, the first thing you should know is that VFP is the only 
instruction set on the A9 that supports double precision. It is a scalar 
instruction set, and fully IEEE compliant. Almost all ARM gcc versions 
support VFP, and ATLAS 3.10 should compile and run without problems.

The Cortex A9 manual says a VFP multiply-add in double precision runs in 
2 cycles, so 1 flops/cycle/core is the theoretical peak. A 1 GHz A9 gets 
more like 0.7 flops/cycle/core, and because it seems that the memory 
interface is a significant bottleneck, you may find a lower number on 
the 1.7 GHz version.

The best source for information about the Cortex processors is ARM: 
http://www.arm.com/products/processors/cortex-a/index.php. Choose your 
processor from the list on the left, go to that page, and under the 
Resources tab, you can read and download the reference manuals.

For example, the A9 VFP reference manual is at:

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0408i/index.html


On 06/14/2013 05:43 AM, José Luis García Pallero wrote:
> Hello:
>
> I'm temptated to buy an ODROID-U2 board 
> (http://www.hardkernel.com/renewal_2011/products/prdt_info.php?g_code=G135341370451), 
> that comes with an ARM Cortex-A9 Exynos 4412 Quad Core 1.7 GHz 
> processor. I would like to compile and run ATLAS on it in order to do 
> some performance tests using DGEMM and DSYRK and I want to know how to 
> compute the theoretical Rpeak for the processor. It has 4 cores at 1.7 
> GHz (2 GHz if it is overclocked), and I have read that supplies also 
> the VFPv3 instructions set. How about VFPv3? Is a vector extension to 
> perform SIMD? How many double precission instructions can do it per 
> clock cycle? Is supported in ATLAS?
>
> And probably this question should have been the first one: has anyone 
> checked ATLAS on an ODROID-(X2/U2)
>
> Cheers
>
> -- 
> *****************************************
> José Luis García Pallero
> jgp...@gm... <mailto:jgp...@gm...>
> (o<
> / / \
> V_/_
> Use Debian GNU/Linux and enjoy!
> *****************************************


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