A suite of data structures and routines for the scalable (parallel) solution of
scientific applications modeled by partial differential equations. It supports
MPI, and GPUs through CUDA or OpenCL, as well as hybrid MPI-GPU parallelism.
PETSc (sometimes called PETSc/Tao) also contains the Tao optimization software
library.

WWW: http://www.mcs.anl.gov/petsc