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Version 1.4.2

28th July 2022

HSL_MC69: Matrix format converter

HSL_MC69 offers routines for converting matrices held in a number of sparse matrix formats to the compressed sparse column (CSC) format used by many HSL routines. This format requires the entries within each column of \(\mathbf{A}\) to be ordered by increasing row index. For symmetric, skew symmetric or Hermitian matrices, only entries in the lower triangle are held. This format is the one used by many of the recent HSL packages; we shall refer to it as the standard HSL format.

Routines are offered for converting matrices held in lower or upper compressed sparse column format or in lower or upper compressed sparse row format or in coordinate format, and for verification and correction of matrices believed to already be in standard HSL format. The conversion routines check the user-supplied data for errors and handle duplicate entries (they are summed) and out-of-range entries (they are discarded).