fftw-calc

A platform-independent command line program to estimate the number of FLOPS (floating-point operations per second) required to compute streaming FFT (Fast Fourier Transform) according to sample rate.

It can be useful to determine of the computer system you wish to use for SDR (Software Defined Radio) is capable of handling the processing you wish to do.

The project was originally started as a learning exercise into setting up the CMake build system.

Contents

The directory structure is as follows:

  <project>/src/
      CMakeLists.txt         - CMake configuration
      cpuid.{c,h}            - Alexander Yee's CPU capabilities code (modified)
      fftw-calc.c            - The program
  <project>/dependencies/fftw/
      CMakeLists.txt         - CMake automation to download/configure FFTw

How to Compile

Using a shell or command prompt window, create a directory and launch CMake. It should build an appropriate makefile or project which you can then use to build the software. Ex:

  mkdir build
  cd build
  cmake ../src

To execute on Linux/MinGW/etc:

  make
  ./fftw-calc --help

To execute on Windows/MSVC/etc:

  msbuild fftwcalc.sln /P:Configuration=Release
  Release\fftw-calc --help

Tested On

Linux/GNU Radio Live DVD 3.7.9.1, FFTW 3.3.4, GCC 4.8.

Win7 32-bit, FFTW 3.3.4, MSVC++ Express 2013

• NB: used cmd> cmake ../src
• NB: the first time you run it, it will ask you to manually extract the fftw distribution in ../dependencies/fftw
• NB: then please re-run the cmake command above
• NB: used cmd> msbuild fftwcalc.sln /P:Configuration=Release

NOTE: For Windows builds, the .dll has to be in the same folder as the .exe or somewhere in the path. The project file generated by cmake will do this for you. NOTE: For MSVC projects, be sure to select the 'fftw-calc' project and make it the start up project before trying to execute the program in the debugger.

Previously Tested On June 2015

When this project was under RASDR/host/fftw-calc, these environments had previously worked, but it has been a while and a few adjustments were needed when testing with the GNU Radio Live DVD. They need to be re-tested.

Linux/CentOS 6, FFTW 3.3.3, GCC 4.4.7

• NB: this just worked as above

MacOS 10.8.5, MACPORTS, FFTW 2.1.5, GCC 4.7.3

• NB: used $ CC=gcc-mp-4.7 CXX=g++-mp-4.7 cmake ../src
• NB: used $ make

Win7 32-bit, FFTW 3.3.3, MSVC++ Express 2010 WinXP 32-bit, FFTW 3.3.3, MSVS 8 2005

• NB: ran 'lib /def:libfftw3-3.def' in the ../dependencies/fftw
• NB: used cmd> cmake ../src
• NB: used cmd> msbuild fftwcalc.sln /P:Configuration=Release
• NB: beware, after I installed MSVC++ Express 2013, the commandline for 2010 broke but I could still build in the GUI -- cmake finds registry entries?

Win7 32-bit, FFTW 3.3.3, MinGW 3.20

• NB: used cmd> cmake -G "MinGW Makefiles" ../src
• NB: used cmd> mingw32-make

Win7 32-bit, FFTW 3.3.3, Code::Blocks 12.11/MinGW 3.20

• NB: used cmd> cmake -G "CodeBlocks - MinGW Makefiles" ../src
• NB: used cmd> c:\codeblocks\codeblocks.exe --rebuild --target=fftw-calc --no-batch-window-close fftwcalc.cbp
• NB: depending on your environment variables and path settings, you may also need to do something like:

• cmd> cmake -G "CodeBlocks - MinGW Makefiles" -DCMAKE_C_COMPILER=c:/codeblocks/MinGW/bin/gcc.exe -DCMAKE_CXX_COMPILER=c:/codeblocks/MinGW/bin/g++.exe -DCMAKE_MAKE_PROGRAM=c:/codeblocks/MinGW/bin/mingw32-make.exe ../src
  

• with 'c:\codeblocks\' being where I installed Code::Blocks 12:11
  

• in this case, the compiler had OpenMP disabled (it wouldnt recognize it)
  

TODO

• Explore use of mingw-w64
• Find out why different builds of fftw behave different. E.g:

GNU Radio Live DVD 3.7.9.1 w/native fftw fftw-3.3.3-sse2-avx:

$ test.1/fftw-calc 2048 2e6 0.0 0
FFT(2048,measured):
(dft-ct-dit/64
  (dftw-direct-64/252 "t2fv_64_sse2")
  (dft-direct-32-x64 "n2fv_32_sse2"))
FLOPS: add=25824 mul=8000 fma=2688 total=39200 Flops/frame
FS=2.00MHz, 0.00% overlap, 38.28 MFlops (by measure method)
Current CPU = Intel(R) Pentium(R) Dual  CPU  E2140  @ 1.60GHz
CPU Threads = 2

GNU Radio Live DVD 3.7.9.1 w/re-built fftw 3.3.4:

$ build/fftw-calc 2048 2e6 0.0 0
FFT(2048,measured):
(dft-ct-dit/32
  (dftw-direct-32/62 "t1_32")
  (dft-direct-64-x32 "n1_64"))
FLOPS: add=47616 mul=11904 fma=9344 total=78208 Flops/frame
FS=2.00MHz, 0.00% overlap, 76.38 MFlops (by measure method)
Current CPU = Intel(R) Pentium(R) Dual  CPU  E2140  @ 1.60GHz
CPU Threads = 2

Ok, it seems obvious that how you build fftw makes a difference, but how to document and describe that so that you build in the most efficient way... This is a good place to start.

I confirm that by using ./configure --enable-sse2 --enable-avx when building fftw 3.3.4, I get the same performance as the native fftw 3.3.3-sse2-avx that came with GNU Radio Live DVD 3.7.9.1

References

• Matteo Frigo and Steven G. Johnson. FFTW
• Pioneer Hill Software, LLC FFT Overlap Processing
• jonolafur cli-fft
• Pau Garcia i Quiles Learning CMake
• Alexander J. Yee FLOPS Project
• rf-sampler