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NTPoly
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NTPoly is a massively parallel library for computing the functions of sparse, symmetric matrices based on polynomial expansions. For sufficiently sparse matrices, most of the matrix functions in NTPoly can be computed in linear time.
NTPoly is freely available and open source under the MIT license. It can be downloaded from the Github repository. We of course recommend that you download a release version to get started.
Installing NTPoly requires the following software:
The following optional software can greatly enhance the NTPoly experience:
NTPoly uses CMake as a build system. First, take a look in the Targets directory. You'll find a list of .cmake files which have example configurations on popular systems. You should copy one of these files, and create your own mymachine.cmake file. Then, cd into the Build directory, and type:
cmake -DCMAKE_TOOLCHAIN_FILE=../Targets/mymachine.cmake ..
There are a few options you can pass to CMake to modify the build. You can set -DCMAKE_BUILD_TYPE=Debug for debugging purposes. You can set the install directory using the standard -DCMAKE_INSTALL_PREFIX=/path/to/dir. You can also set -DFORTRAN_ONLY=YES if you want to only build the Fortran interface. Note that with just the Fortran interface, it is not possible to perform local tests.
After that you can build using:
make
And for the documentation:
make doc
Online documentation is also available. Further details about the library can be found on the Wiki. If you aren't cross compiling, you can perform local tests using:
make test
The theory of matrix functions is a long studied branch of matrix algebra. Matrix functions have a wide range of applications, including graph problems, differential equations, and materials science. Common examples of matrix functions include the matrix exponential:
f(A) = e^A.
from the study of networks, or the inverse square root:
f(A) = A^(-1/2)
from quantum chemistry. NTPoly is a massively parallel library that can be used to compute a variety of matrix using polynomial expansions. Consider for example the Taylor series expansion of a function f(x) .
f(x) = f(0) + f'(0)x + f''(0)x^2/2! + ...
We can imagine expanding this from the function of a single variable, to a function of a matrix:
f(A) = f(0) + f'(0)A + f''(0)A^2/2! + ...
where matrices can be summed using matrix addition, and raised to a power using matrix multiplication. At the heart of NTPoly are polynomial expansions like this. We implement not only Taylor expansions, but also Chebyshev polynomial expansions, and other specialized expansions based on the function of interest.
When the input matrix A and the output matrix f(A) are sparse, we can replace the dense matrix addition and multiplication routines with sparse matrix routines. This allows us to use NTPoly to efficiently compute many functions of sparse matrices.
In the examples directory, there are a number of different example programs that use NTPoly. You can check the ReadMe.md file in each example directory to learn how to build and run each example. The simplest example is PremadeMatrix, which includes sample output you can compare to.
The following features and methods have been implemented in NTPoly:
A description of the techniques used in NTPoly can be found in the following Computer Physics Communications paper:
Dawson, William, and Takahito Nakajima. "Massively parallel sparse matrix function calculations with NTPoly." Computer Physics Communications (2017).
Please cite this paper in accordance to the practices in your field.
To begin contributing to NTPoly, take a look at the Wiki pages. The https://github.com/william-dawson/NTPoly/blob/master/CONTRIBUTING.md "Contributing Guide" provides an overview of best development practices. Additionally, there is a Adding New Functionality page which documents how one would go about adding a matrix function to NTPoly.
1.8.14