This is a minimum code to investigate the behaviour of PETSc when user-defined matrices are used. It can be compiled using
make
and run using
./petsc-test ...
Options are -d to use "direct" access to the user-defined matrix,
rather than through the PETSc interface;-k to specify a KSP options
file; -n to specify the size of the system of equations to be
generated and solved.
Running
./petsc-test -k ksp-options -n 32
generates and solves a random system of 32 equations, using the PETSc GMRES solver. The right hand side is generated by multiplying a reference solution by the system matrix, through the PETSc interface.
Calling with the -d option
./petsc-test -k ksp-options -n 32 -d
performs the same calculation, but with the right hand side generated operating on the user data, rather than using the PETSc interface.