Installing PETSc

PETSc needs to be installed on the machine and the environment variables PETSC_ARCH and PETSC_DIR have to be set to compile EllPETSc. PETSc can obtained for free at http://www-fp.mcs.anl.gov/petsc/. Cactus needs to be compiled with MPI. While PETSc can be compiled for single processor mode (without MPI), Cactus has only been tested and used with the parallel version of PETSc requiring MPI. For detailed information in how to install PETSc refer to the documentation.