Antitriangular factorization

Antitriangular factorization of symmetric matrices

Antitriangular factorization of symmetric matrices


To compute the antitriangular factorization of a symmetric matrix. The software provided below may only be used for academic purposes. It is not tested thoroughly and should be understood as research code. Please contact Zvonimir Bujanovic or Daniel Kressner before intending to include this software in academic production code or commercial libraries.


tar ball antitriangular.tar.gz.

Warning: To compile any of the files above you need BLAS and LAPACK.

Among others, the tar ball contains the following files:

  • antitriangularsmall.f
    Implementation of the scalar algorithm described in [Mastronardi/Van Dooren'2013].
  • antitri_NB.f
    Implementation of the block algorithm described in [Bujanovic/Kressner'2014].


  1. N. Mastronardi and P. Van Dooren. The antitriangular factorization of symmetric matrices. SIAM J. Matrix Anal. Appl., 34(1):173-196, 2013.
  2. Z. Bujanovic and D. Kressner. A block algorithm for computing antitriangular factorizations of symmetric matrices. November 2014.