Project Homepages: http://www.mcs.anl.gov/petsc
                                http://www.llnl.gov/casc/linear_solvers/

Objective #1: Develop interfaces for various preconditioners and solvers developed at LLNL within the hypre library to make them directly usable with PETSc. and ISIS++ This will leverage the strong numerical analysis development of linear solvers at LLNL, and make it available to the wide audience of PETSc and ISIS++ users. It will allow LLNL to concentrate on solver development and not have to re-invent the parallel computing infrastructure that PETSc and ISIS++ provide.

Objective #2:  Develop interfaces for solvers, matrices, and other PETSc and ISISconstructs from the hypre interface. This allows a user to use the combined capabilities of these packages from either package's interface. Hypre users used to, say, the Structured Grid Interface to its parallel structured multigrid codes, can compare the convergence and performance of PETSc and/or ISIS solvers without changing their interface.

Approach:

(1) Implement hypre preconditioners in terms of an abstract matrix interface when possible, and wrap PETSc matrices with that interface. In this way, hypre preconditioner code is compatible with PETSc matrix data structures, allowing PETSc to utilize them.

(2) Define "physics-based" conceptual interfaces that are appropriate for applications writers, such as the Structured Grid Interface, and allow the chosen solver to build an appropriate data structure. In this way, the exact same interface can be used to build a data structure appropriate for solvers in hypre, PETSc, or both.

(3) Wrap PETSc solvers in a hypre interface.

Recent FY98 accomplishments:

(1) A fully parallel incomplete factorization with dual-thresholding preconditioner, PILUT, has been implemented in terms of an abstract matrix definition that is compatible with PETSc, and is available for use by PETSc users.

(2) Implementations for the Structured Grid Interface on top of PETSc have been made and the full suite of PETSc solvers are available from this interface, in combination with the PILUT preconditioner.

(3) Petsc solvers are available from a hypre wrapper level.

Plans for FY99:

Additional preconditioners, such as ParaSails, a sparse approximate inverse preconditioner, and BoomerAMG, a parallel algebraic-multigrid preconditioner, will be made compatible with PETSc's data structures through the matrix abstraction paradigm. Additional physics-based interfaces, including implementations of SNL's  Finite Element Interface , and/or a Structured Adaptive Mesh Refinement interface appropriate for projects such as  SAMRAI , will be implemented on top of hypre preconditioners and PETSc's solvers, though this work will likely carry on into FY2000.  ISIS will be brought up to the same level of wrappers as PETSc, probably through the ESI.

Tool availability: PETSc is fully available from its web-pages and installed on the NERSC system, support is provided via petsc-maint@mcs.anl.gov. Hypre has not been officially released and is not yet available as a library. Selected routines are available from the authors to a limited ACTS audience by contacting them directly. See the CASC linear solver web page for addresses.  ISIS++ is available from their webpage.

Participants and affiliations:
Satish Balay, Lois Curfman McInnes, Barry Smith - Argonne National Laboratory
Andy Cleary, Rob Falgout, Edmond Chow - Lawrence Livermore National Laboratory
Robert Clay, Alan Williams, Ben Allen, Noel Nachtigal - Sandia National Laboratories

Related projects: Aztec-PETSc, ESI