From: Wolfgang Bangerth Date: Sat, 20 Jan 2018 00:37:19 +0000 (-0700) Subject: Update a comment for PETScWrappers::PreconditionBlockJacobi. X-Git-Tag: v9.0.0-rc1~547^2 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F5765%2Fhead;p=dealii.git Update a comment for PETScWrappers::PreconditionBlockJacobi. --- diff --git a/include/deal.II/lac/petsc_precondition.h b/include/deal.II/lac/petsc_precondition.h index 954d55ce30..f73a83946c 100644 --- a/include/deal.II/lac/petsc_precondition.h +++ b/include/deal.II/lac/petsc_precondition.h @@ -185,9 +185,15 @@ namespace PETScWrappers /** * A class that implements the interface to use the PETSc Block Jacobi - * preconditioner. The blocking structure of the matrix is determined by the - * association of degrees of freedom to the individual processors in an MPI- - * parallel job. If you use this preconditioner on a sequential job (or an + * preconditioner. PETSc defines the term "block Jacobi" as a preconditioner + * in which it looks at a number of diagonal blocks of the matrix and then + * defines a preconditioner in which the preconditioner matrix has the same + * block structure as only these diagonal blocks, and each diagonal block + * of the preconditioner is an approximation of the inverse of the + * corresponding block of the original matrix. + * The blocking structure of the matrix is determined by the + * association of degrees of freedom to the individual processors in an + * MPI-parallel job. If you use this preconditioner on a sequential job (or an * MPI job with only one process) then the entire matrix is the only block. * * By default, PETSc uses an ILU(0) decomposition of each diagonal block of