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I am looking for a quick and easy program to estimate FLOPS on my Linux system. I found HPL, but getting it compiled is proving to be irritating. All I need is a ballpark estimate of the FLOPS, without needing to spend a day researching benchmark packages and installing dependent software. Does any such program exist? Would it be sufficient to write a C program that multiples two floats in a loop?

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6 Answers

up vote 4 down vote accepted

The question is what do you mean by flops? If all you care about is how many of the simplest floating point operations per clock, it is probably 3x your clock speed, but that is about as meaningless as bogomips. Some floating point ops take a long time (divide, for starters), add and multiply are typically quick (one per fp unit per clock). The next issue is memory performance, there is a reason the last classic CRAY had 31 memory banks, ultimately CPU performance is limited by how fast you can read and write to memory, so what level of caching does your problem fit in? Linpack was a real benchmark once, now it fits in cache (L2 if not L1) and is more of a pure theoretical CPU benchmark. And of course, your SSE (etc) units can add floating point performance too.

What distro do you run?

This looked like a good pointer: http://linuxtoolkit.blogspot.com/2009/04/intel-optimized-linpack-benchmark-for.html

http://onemansjourneyintolinux.blogspot.com/2008/12/show-us-yer-flops.html

http://www.phoronix-test-suite.com/ might be an easier way to install a flops benchmark.

Still I do wonder why you care, what you are using it for? If you just want a meaningless number, your systems bogomips is still right there in dmesg.

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Phoronix seems to be exactly what I was looking for - thank you! The only reason I wanted this was because I was filling out a survey that asked how many teraflops of computing power I have. The survey wasn't terribly important, so I wasn't concerned about the accuracy of the answer. Still, it would be kind of neat to be able to say, "Our cluster can do X teraflops." Though as you point out, that number doesn't necessarily have much real-world meaning. –  molecularbear Nov 26 '09 at 2:06
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I highly recommend the ready-to-run linpack build from Intel: http://software.intel.com/en-us/articles/intel-math-kernel-library-linpack-download/

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As you mention cluster, we have used the the HPCC suite. It takes a bit of effort to setup and tune, but in our case the point wasn't bragging per se, it was part of the acceptance criteria for the cluster; some performance benchmarking is IMHO vital to ensure that the hardware works as advertised, everything is cabled together correctly etc.

Now if you just want a theoretical peak FLOPS number, that one is easy. Just check out some article about the CPU (say, on realworldtech.com or somesuch) to get info on how many DP FLOPS a CPU core can do per clock cycle (with current x86 CPU's that's typically 4). Then the total peak FLOPS is just

number of cores * FLOPS/cycle * frequency

Then for a cluster with IB network you should be able to hit around 80% of the peak FLOPS on HPL (which BTW is one of the benchmarks in HPCC).

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One benchmark that has been traditionally used to measure FLOPS is Linpack. Another common FLOPS benchmark is Whetstone.

More reading: The Wikipedia "FLOPS" entry, Whetstone entry, Linpack entry

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I appreciate your answer, however my goal is to obtain a quick n' dirty estimate of flops. Whetstone and Linpack have the same problem as HPL - I start reading about it, then get lost in site after site that all look 20 years old. When I do manage to find source code, I can't seem to compile it without installing a bunch of dependent libraries - even then I run into errors. I could get all this stuff working, but it's not important enough to spend the time. Hopefully there exists some relatively modern software that Just Works for ballparking flops. –  molecularbear Nov 25 '09 at 22:32
    
Estimate? Then it's about 4*Hz: for 1GHz CPU it's about 4GFLOPS :)) –  kolypto Nov 26 '09 at 1:43
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LinX is great.It's extremely simple.

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apparently there's a "sysbench" package and command:

sudo apt-get install sysbench

sysbench --test=cpu --cpu-max-prime=20000 run

ref: http://www.midwesternmac.com/blogs/jeff-geerling/2013-vps-benchmarks-linode

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