Benchmark philosophical question...

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi guys,

I’m thinking of benchmarks between GPU and CPU. I’ve read a lot of papers where people benchmark CUDA software executed on a GPU device and the same algorithm executed on one single core…
I don’t think this is politically correct…

What’s your idea about this?

What’s the way to do a correct benchmark in your point of view?
GPU algorithm is obviously written with the aim of exposing the highest level of parallelism, the same algorithm on a different architecture should be rewritten…

So, any suggestion?

luca

2

I think you should always compare times with wall clock. If a process takes X seconds to complete on your machine - using CPU power only - then you

should check how much time it takes to complete using the GPU or GPUs in your system. You now can divide the factor by the number of CPU cores on

your machine (or not divide and say that one GPU equals Y such quad core machines - assuming the CPU code ran on all the cores)

Its only semantics… :)

The important thing to make sure is that you indeed measure the same work done on CPU and GPU, the GPU results are correct.

eyal

3

You can’t have a clean comparison between GPU and CPU algorithms because for a start any GPU algorithm still requires a little help from the CPU as well. The appropriate thing to do - when you really want to (or must) compare to CPU implementations - is: take the best implementation of the fastest known CPU algorithm and compare yourself to that.

4

But when I’m given a code (the only extant version of its algorithms) which uses BLAS to do a lot of 2x2 matrix multiplications, am I supposed to fix that little oversight prior to benchmarking?

5

Thank you guys, your ideas are really interesting!!

Jjp idea is really correct in my point of view, but sadly no good implementation for CPU of something similar to my GPU algorithm exist…
Sorry Eyal… Wat’s exactly “wall time”? I like a lot your idea… :-)

Many thanks,

luca

6

Time measured by the clock hanging on your office wall.

7

:D Ohhh… Thank you YDD!
I’m not English… I was imaging strange things…

luca