r83_np, a FORTRAN90 code which carries out some basic linear algebra operations on R83_NP matrices (real 64 bit precision tridiagonal 3xN format, nonpivoting factorization).

These utilities are distinguished by the fact that an LU factorization is attempted without the use of pivoting. Such an approach will fail if a zero pivot is encountered, and will generally not be as accurate as a pivoting factorization. It is only recommended in cases where pivoting is known to be unnecessary, such as for a symmetric positive definite matrix.


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.


r83_np is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and Programs:


linear_algebra, Fortran90 codes which carry out various linear algebra operations for matrices stored in a variety of formats.

Source Code:

Last revised on 16 August 2022.