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roddomi
Journeyman III
‎09-14-2010 10:17 PM

SKA and ALU:Fetch ratio

Hi,

I am using the Stream KernelAnalyzer 1.6 to tune some of my applications. What is a good number for the ALU:Fetch ratio? From the SKA release notes it seems 1.0 is the "sweet spot". Is that the case? What's the reasoning behind that? I'd like to know more about this metric.


Thank you.

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3 Replies
n0thing
Journeyman III
‎09-15-2010 03:09 AM

Read section 1.6 i.e 'GPU Compute Device Scheduling' of the OpenCL programming guide to understand why ALU:Fetch ratio is important to keep the GPU busy.

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roddomi
In response to n0thing
Journeyman III
‎09-15-2010 01:02 PM

So if I am comparing two implementations of the same algorithm, the higher the ALU:Fetch ratio the better?

Thank you.

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ryta1203
In response to roddomi
Journeyman III
‎09-15-2010 07:42 PM

No, this is not accurate.

For example, if you are ALU bound adding ALU operations is only going to increase your runtime.

Also, if you are memory bound you aren't going to get any performance benefit by adding useless ALU operations (providing all else is equal).

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