[petsc-dev] ViennaCL-bindings in next

[Nystrom, William D]

Karli,

Would the OpenCL headers and libraries that come with Cuda 5.0 be adequate?

Thanks,

Dave

________________________________________
From: petsc-dev-bounces at mcs.anl.gov [petsc-dev-bounces at mcs.anl.gov] on behalf of Karl Rupp [rupp at mcs.anl.gov]
Sent: Thursday, March 21, 2013 5:50 PM
To: For users of the development version of PETSc
Subject: [petsc-dev] ViennaCL-bindings in next

Hi,

the interface to ViennaCL [1] has just been merged to 'next', enabling
PETSc to use OpenCL-enabled devices (most notably Intel's Xeon Phi and
GPUs from AMD in addition to the existing NVIDIA bindings). I tested it
with Vector-, Matrix-, and KSP- examples.

The new bindings are enabled by the configure flags
--download-viennacl
--with-opencl-include=/path/to/OpenCL-Headers
--with-opencl-lib=/path/to/libOpenCL.so

The OpenCL headers can be obtained on the Khronos webpage [2] and are
often available via package managers, e.g.
$> sudo apt-get install opencl-headers
or
$> sudo yam install opencl-headers
In such case, the OpenCL include directory is typically /usr/include
(BuildSystem may not detect these headers correctly on Mac OS, I'm
working on this). The OpenCL library comes with your graphics driver and
is usually located at /usr/lib/. There is no separate compiler as for
CUDA needed!

FAQ:

- What is the performance difference between OpenCL and CUDA for GPUs?
My experience is that for large problem sizes they are equivalent for
almost all linear algebra kernels. For small problem sizes (kernel
execution less than 1ms), CUDA is currently superior because of lower
latency.

- Which solvers can I use with the ViennaCL-bindings?
The same as with CUSP. Most notably the usual CG, BiCGS, GMRES.

- Which preconditioners are provided in the ViennaCL-bindings?
Currently none. You can, however, use all the standard CPU-based
preconditioners in PETSc together with ViennaCL matrices and vectors.

- Which command line options do I need to use?
Use -vec_type viennacl -mat_type aijviennacl
On Intel's Xeon Phi you also need to pass -viennacl_device_accelerator.
(If you read this email in an archive: Check the manual for current flags).

Best regards,
Karli

[1] http://viennacl.sourceforge.net/
[2] http://www.khronos.org/registry/cl/