PETSc, pronounced PET-see (the S is silent), is 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.
Cray provides PETSc as part of the programming environment.
nersc$ module load cray-petsc
Current documentation is available through the
intro_petsc man page:
nersc$ module load cray-petsc nersc$ man intro_petsc