Schwarz Library

Performance results

1. Paper in IJHPCA; Alternative arXiv version
2. Two stage update

Required components

The required components include:

1. Ginkgo: The Ginkgo library is needed. It needs to be installed and preferably the installation path provided as an environment variable in Ginkgo_DIR variable.
2. MPI: As multiple nodes and a domain decomposition is used, an MPI implementation is necessary.

Quick Install

Building Schwarz-Lib

To build Schwarz-Lib, you can use the standard CMake procedure.

mkdir build; cd build
cmake -G "Unix Makefiles" .. && make

By default, SCHWARZ_BUILD_BENCHMARKING is enabled. This allows you to quickly run an example with the timings if needed. For a detailed list of options available see the Benchmarking page.

For more CMake options please refer to the Installation page

Currently implemented features

1. Executor paradigm:

• GPU.
• OpenMP.
• Single rank per node and threading in one node.

1. Factorization paradigm:

• CHOLMOD.
• UMFPACK.

2. Solving paradigm:

• Direct:

• Ginkgo.
• CHOLMOD.
• UMFPACK.

• Iterative:

• Ginkgo.
• deal.ii.

3. Partitioning paradigm:

• METIS.
• Regular, 1D.
• Regular, 2D.
• Zoltan.

4. Convergence check:

• Centralized, tree based convergence (Yamazaki 2019).
• Decentralized, leader election based (Bahi 2005).

5. Communication paradigm.

• Onesided.
• Twosided.
• Event based.

5. Communication strategies.

• Remote comm strategies:
  • MPI_Put , gathered.
  • MPI_Put , one by one.
  • MPI_Get , gathered .
  • MPI_Get , one by one.
• Lock strategies: MPI_Win_lock / MPI_Win_lock_all .
  • Lock all and unlock all.
  • Lock local and unlock local.
• Flush strategies: MPI_Win_flush / MPI_Win_flush_local .
  • Flush all.
  • Flush local.

6. Schwarz problem type.

• RAS.
• O-RAS.

Any of the implemented features can be permuted and tested.

Known Issues

1. On Summit, the Spectrum MPI seems to have a bug with using MPI_Put with GPU buffers. MPI_Get works as expected. This bug has also been confirmed with an external micro-benchmarking library, OSU Micro-Benchmarks.

For installing and building, please check the Installation page

Credits: This code (written in C++, with additions and improvements) was inspired by the code from Ichitaro Yamazaki, ICL, UTK.