A GPU based FX correlator for radio astronomy
Cuda C C++ Objective-C Shell Prolog
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Release Notes for xGPU v0.0.1


xGPU is a library for performing the cross-multiplication step of the
FX correlator algorithm, which is popular for radio astronomy signal

Software Compatibility:

The library has been tested under Linux (Ubuntu 10.04 and 10.10) and
Mac OS X using release 4.0 of the CUDA toolkit.  Default compilation
creates a 32-bit binary, so 64-bit systems will require 32-bit c and
c++ libraries installed for cross-compilation (gcc and g++ multilib).

Hardward Compatibility:

For a list of supported devices see,


While this library will run on pre-Fermi GPUs with appropriate changes
to the Makefile, note that the kernels make Fermi-specific
optimizations and so will likely lead to sub-standard performance on
sm1.x CUDA architectures.  Initial tuning has taken place for the
Kepler architecture, but this is far from complete.

Building the Library:

The library, library query tool "xgpuinfo", and the sample program
"cuda_correlator" can be built by changing into the src subdirectoy
and running "make".

  $ cd src
  $ make

Currently, a number of sizing parameters must be specified when
building the library.  Default values of these parameters are
specified near the top of src/xgpu_info.h.  The default values can be
overridden on the make command line to suit your instrument's needs.
The options that can be given on the make command line are shown here
with there default values.


Note that NTIME_PIPE must be a multiple of 4 and NTIME must be a
multiple of NTIME_PIPE.  The preprocessor will error out if those two
conditions are not met.

For example, to compile with NSTATION set to 128 and all other
parameters at their default values:
  $ make NSTATION=128

Installing the Library:

The library can be installed by changing into the src subdirectoy and
running "make install".  By default, this will install xgpuinfo into
/usr/local/bin, xgpu.h into /usr/local/include, and libxgpu.so (or
libxgpu.dll on Cygwin) to /usr/local/lib.  Specifying
"prefix=/some/path" on the "make install" command line will install
these files into /some/path/bin, /some/path/include, and
/some/path/lib instead.

  $ cd src
  $ make install                    # install under /usr/local
  $ make install prefix=$HOME/local # install under $HOME/local

Using the Library:

The library can be called from C or C++ code.  To use the library,
your source files need to #include <xpgu.h> and your executable needs
to be linked with libxpgu.so (or libxgpu.dll on Cygwin).  On UNIX
systems, this usaually means adding "-L/path/to/lib/dir" and "-lxpgu"
to the link command line.

Please see the comments in xgpu.h as well as the usage in the sample
program cuda_correlator.cu for more details on how to use the library.

This library has been designed to be interfaced with other parts of an
FX correlator pipeline, and so not much can be achieved in isolation.
A simple test program "cuda_correlator.cu" is included which performs
cross-multiplication on the host and the device and verifies the
device obtained the correct answer.  The many options regarding number
of stations, frequency channels etc. are set in the top of this file.

Benchmarking Performance:

xGPU includes an additional benchmarking utility: CUBE - CUDA
BEnchmarking.  This uses C-preprocessor directive to obtain arithmetic
throughput and device memory bandwidth performance.  To invoke a
benchmarking run, one simply has to execute the "bench" script.  This
will perform four runs of the test.  The first two of these are
concerned with counting all flops and transfers performed by the
kernels, and measuring the time taken for each of these steps.  The
latter two are concerened with measuring the asynchronous performance
of the device<->host transfers.  By default the results are printed to
stdout, though they are output to file (cube_benchmark.log and

Acknowledging xGPU:

If you find this code useful in your work, please cite:

M. A. Clark, P. C. La Plante, and L. J. Greenhill, "Accelerating Radio
Astronomy Cross-Correlation with Graphics Processing units",
[arXiv:1107.4264 [astro-ph]].


Michael Clark (NVIDIA)
Paul La Plante (Loyola University Maryland)
Lincoln Greenhill (Harvard-Smithsonian Center for Astrophysics)
David MacMahon (University of California, Berkeley)
Ben Barsdell (Harvard-Smithsonian Center for Astrophysics)