[petsc-dev] Update to ViennaCL 1.5.1 done

[Karl Rupp]

Hi guys,

today I finally completed the update of the bindings to ViennaCL 1.5.1, 
which brings, among some performance improvements, also the missing 
implementation of distributed MPI/OpenCL-based matrix-vector products 
using the compressed CSR format. As a consequence, PETSc can now be used 
with any OpenCL-capable device (most notably AMD and NVIDIA GPUs, but 
also Intel's MIC architecture) in a full MPI environment. Since there is 
no need to hide our OpenCL capabilities, particularly as it is far less 
a burden on the build system, can be used with any host compiler, and is 
not restricted to a single vendor, I updated the webpage accordingly here:
https://bitbucket.org/petsc/petsc/commits/c738b73485b3ba70a7722f0a4f5092a7fe93ee87

Please let me know if there are any objections, otherwise I will merge 
this to master soon (i.e. once all nightly-tests pass).

There is of course still plenty of work and optimizations ahead, 
particularly the vector scatters (both CUDA/CUSP and OpenCL/ViennaCL).

@Jed: Can you please update the repository description here: 
https://bitbucket.org/petsc/petsc/ by replacing "NVIDIA GPUs" 
accordingly, e.g. "GPUs through CUDA and OpenCL" (or any other more 
elegant formulation)?

Thanks and best regards,
Karli