Sparsity structure and Gaussian elimination

  • Authors:
  • I. S. Duff;A. M. Erisman;C. W. Gear;J. K. Reid

  • Affiliations:
  • Boeing Computer Services, Inc., Seattle, WA;Boeing Computer Services, Inc., Seattle, WA;Univ. of Illinois, Urbana;Harwell Laboratory, Oxon, UK

  • Venue:
  • ACM SIGNUM Newsletter
  • Year:
  • 1988

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Abstract

In this paper we collate and discuss some results on the sparsity structure of a matrix. If a matrix is irreducible, Gaussian elimination yields an LU factorization in which L has at least one entry beneath the diagonal in every column except the last and U has at least one entry to the right of the diagonal in every row except the last. If this factorization is used to solve the equation Ax=b, the intermediate vector has an entry in its last component and the solution x is full. Furthermore, the inverse of A is full.Where the matrix is reducible, these results are applicable to the diagonal blocks of its block triangular form.