MPI+OpenMP methods for implementing the conjugate gradient method with the IC(0) preconditioner based on the use of grid node reordering

The paper considers two ways of using MPI and MPI+OpenMP technologies for constructing and inverting the preconditioner of an incomplete triangular Cholesky decomposition without filling IC(0) for solving systems of linear algebraic equations with an arbitrary symmetric positive definite matrix. They differ in the way in which the preconditioning matrix IC(0) is computed. Methods of using MPI and MPI+OpenMP technologies are based on the use of grid node orderings consistent with the division of the calculation area. The use of OpenMP technology in the construction and inversion of the preconditioner is carried out for most rows of the matrix. Comparative timing results for the MPI+OpenMP and MPI implementations of the proposed preconditioning used with the conjugate gradient method for a model problems and the sparse matrix collections SuiteSparse as well as comparing the time of solving these problems using two methods of using MPI and MPI + OpenMP technology are presented.