What is STARS-H?

The Software for Testing Accuracy, Reliability and Scalability of Hierarchical (STARS-H)
computations is a parallel library that provides a high performance matrix market of
rank structured matrix operators. STARS-H supports various matrix kernels that are
proxies for many scientific applications, and optionally compresses them by exploiting
their data sparsity. This translates into a lower arithmetic complexity and memory footprint.
STARS-H intends to provide a standard software environment for assessing accuracy and performance
of 𝓗-matrix libraries on a given hardware architecture. STARS-H currently supports
the tile low-rank (TLR) data format for approximation on shared and distributed-memory systems,
possibly equipped with GPUs, using MPI, OpenMP and task-based programming models.

Vision of STARS-H

The vision of STARS-H is to design, implement and provide a community code for
hierarchical matrix generator with support of various data formats for
approximation, including, but limited to, TLR, HSS, HODLR, H and H^2. STARS-H
aspires to be for the low-rank approximation community what UF Sparse Matrix
Collection is for the sparse linear algebra community, by generating
hierarchical matrices coming from a variety of synthetic and real-world
applications. Furthermore, extracting the performance of the underlying
hardware resources (i.e., x86 and GPUs) is in the DNA of STARS-H, since the
approximation phase can be time-consuming on large-scale scientific
applications.

Current Features of STARS-H

This project is WIP, with current features limited to:

The only supported data format is Tile Low-Rank (TLR):

1. TLR Approximation
2. Multiplication of TLR matrix by dense matrix

Programming models (backends):

1. OpenMP
2. MPI
3. Task-based using StarPU (with and without MPI)

Applications in matrix-free form:

1. Cauchy matrix
2. Electrostatics (1/r)
3. Electrodynamics (sin(kr)/r and cos(kr)/r)
4. Random synthetic TLR matrix
5. Spatial statistics (exponential, square exponential and matern kernels)
6. Mesh deformation using radial basis functions, i.e., Gaussian, exponential, inverse quadratic, inverse multi-quadratic, CPTS, and Wendland kernels.
7. Acoustic scattering

Low-rank approximation techniques (low-rank engines):

1. Ordinary SVD,
2. Rank-revealing QR,
3. Randomized SVD.

Additional:

1. CG method for symmetric positive-definite (SPD) systems.

TODO List

1. Add support for more matrix kernels and applications
2. Extend support to hardware accelerators (i.e, GPUs)
3. Provide full StarPU support (GPUs and distributed-memory systems)
4. Port to other dynamic runtime systems
5. Implement additional low-rank routines like ACA.
6. Implement additional formats: HODLR/H/HSS/H^2

Installation

Installation requires at least CMake of version 3.2.3. To build STARS-H,
follow these instructions:

1. Get STARS-H from git repository

   git clone git@github.com:ecrc/stars-h

   or

   git clone https://github.com/ecrc/stars-h

2. Go into STARS-H folder

   cd stars-h

3. Get submodules

   git submodule update --init

4. Create build directory and go there

   mkdir build && cd build

5. Use CMake to get all the dependencies

   cmake .. -DCMAKE_INSTALL_PREFIX=/path/to/install/

6. Build STARS-H

   make -j

7. Run tests (optional)

   make test

8. Build local documentation (optional)

   make docs

9. Install STARS-H

   make install

10. Add line

    export PKG_CONFIG_PATH=/path/to/install/lib/pkgconfig:$PKG_CONFIG_PATH

    to your .bashrc file.

Now you can use pkg-config executable to collect compiler and linker flags for
STARS-H.

Examples

The directory examples contains two subfolders: problem and approximation.
The sources in problem show how to generate problems (e.g., spatial statistics,
minimal or dense) and how to create STARSH_problem instance, required for every
step of STARS-H. The examples in approximation are based on problem generations
and have additional steps on approximation of corresponding matrices.

Important notice: the approximation phase does not require the entire dense matrix
to be stored, since matrix elements are computed on the fly.

Dataset

Please see Data.md for information about dataset.