Example fbench

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This is a guide to the fbench C example project included in the EMAC OE SDK.

How fast does your machine execute floating point operations? How accurate are those operations? This project is a floating point benchmark and accuracy testing application that utilizes ray tracing algorithms. It's also a good example of a method of processor performance comparison and compiler optimization testing. It's an excerpt from the fbench project by John Walker of Fourmilab. See John Walker's Floating Point Benchmarks project homepage for more information.

The fbench project builds two executables: fbench and ffbench.

fbench is a floating point benchmark. It's actually a complete optical design raytracing algorithm based on the Marinchip Interactive Lens Design System. See John Walker's fbench project homepage for more information.

ffbench is a Fast Fourier Transform benchmark. It loops through a fast Fourier transform of a square matrix of complex numbers, reverses the transform and then checks the results. See John Walker's ffbench project homepage for more information.

Opening, Building and Uploading the Project Files

1. Open the C/C++ editing perspective.


2. Open the fbench project files.


3. Build the fbench project.


4. Upload the fbench and ffbench executables to the target machine.


Usage and Behavior

Hardware Requirements

The fbench project is intended for use on C implementations that define int as 32 bits or longer and permit allocation and direct addressing of arrays larger than one megabyte. If your target does not meet these requirements then you're going to have a bad time.

Using fbench

The fbench program is executed from the console. It takes a single optional parameter.

./fbench <itercount>

Where <itercount> specifies the number of iterations to be performed, 1000 being the default.
For archival purposes you'll want to use a value slightly higher than 1000

Usage Example

root@som9g20:/tmp# ./fbench 2000
Ready to begin John Walker's floating point accuracy
and performance benchmark.  2000 iterations will be made.

Measured run time in seconds should be divided by 2
to normalise for reporting results.  For archival results,
adjust iteration count so the benchmark runs about five minutes.

Press return to begin benchmark:

After fbench is finished it prompts us to stop the timer (by pressing return).

Stop the timer:

So we press return...

No errors in results.

...and fbench reports that no errors were found in our floating point operations. Hurrah!

Using ffbench

The ffbench program is executed from the console. It takes no parameters.


Usage Example

root@som9g20:/tmp# ./ffbench
20 passes.  No errors in results.

It runs until it is finished (30 seconds or so, depending on the speed of your machine). It performed 20 iterations of our Fast Fourier Transform dance and discovered no errors.