Build System

Installing PETSc2 required:

• MPI.jl

• ArrayViews.jl

• PETSc itself

Installing Other Dependencies

MPI.jl will be install automatically if it is not already present. The release version of MPI.jl does not work, so the build system installs an older version. Before you install MPI.jl, you must have an MPI implementation installed. Some systems come with MPI pre-installed, others do not. If you are unsure which MPI implementation to install, I recommend MPICH, which is available as a package for Debian-based system.

ArrayViews.jl will also be installed if not present.

Installing PETSc

The build system looks for an existing PETSc installation and only attempts to build PETSc if one is not found. It looks for the PETSC_DIR and PETSC_ARCH environment variables. If they are both present, PETSc is not installed.

If you want the build system to build PETSc, you must first install

• MPI (described in the previous section)

• BLAS

• LAPACK

• Python

Note that PETSc cannot link to the BLAS and LAPACK packaged with Julia. Instead, it links to the system BLAS and LAPACK. The efficiency of PETSc depends on the efficiency of BLAS, so it is recommended to obtain a high-quality BLAS (for example, if you machine has a vendor-provided BLAS implemention) and compile it from source on your machine.

Python is required by the PETSc build system. It is not used by PETSc at runtime.

By default, the build system builds a debug version of PETSc. This enables error checking within PETSc that is useful for debugging, at the cost of some performance. To build an optimized version of PETSc, see the deps/install_petsc.sh script.

Note that arguments passed to the install_petsc.sh script are passed to PETSc's configure command. If you want non-default options, running this script directly (not as part of the build system) is the recommended way to build PETSc. After doing so, set the PETSC_DIR and PETSC_ARCH environment variables before running build.jl (see the next section).

Even if the build system builds PETSc, it is still possible to use other versions of PETSc by setting the PETSC_DIR and PETSC_ARCH environment variables at runtime. If these variables are not present, the version of PETSc built by the build system is used.

Linking other programs to PETSc

The build system generates a file deps/use_petsc.sh. Running source deps/use_petsc.sh will set the PETSC_DIR and PETSC_ARCH environment variables corresponding to the PETSc build by the build system. This enables, for example, compiling C programs against this version of PETSc.

Debugging Install

The PETSc library is installed in deps/petsc-x.y.z, where x.y.z is the current version of PETSc. Inside this directory, PETSc will create a directory for your machine's specific architecture. On my machine the architecture is arch-linux2-c-debug. Inside this directory are the usual /bin, /lib etc. directories.

In the process of building PETSc, output is redirected to log files in the deps/petsc-x.y.z directory. Specifically

• The output of configure is written to fout

• The output of make is written to fout2

• The output of make test is written to fout3

If any of these commands fail, the log files contain detail information that explain what happened.