OpenBLAS is an optimized BLAS library based on GotoBLAS2 1.13 BSD version.
PETSc, pronounced PET-see (the S is silent), is a suite of data structures and routines for the scalable (parallel) solution of scientific applications modeled by partial differential equations.
R is a free software environment for statistical computing and graphics.
ROOT is a data analysis framework.
SageMath is a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more. Access their combined power through a common, Python-based language or directly via interfaces or wrappers.
SCOTCH is a software package and libraries for sequential and parallel graph partitioning, static mapping, and sparse matrix block ordering, and sequential mesh and hypergraph partitioning.
SPECFUN is a FORTRAN90 library which evaluates certain special functions, by William Cody and Laura Stoltz.
Voro++ is a open source software library for the computation of the Voronoi diagram, a widely-used tessellation that has applications in many scientific fields.