LQ-Schur projection on large sparse matrix equations

Daniel Boley, Todd Goehring

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


A new paradigm for the solution of non-symmetric large sparse systems of linear equations is proposed. The paradigm is based on an LQ factorization of the matrix of coefficients, i.e. factoring the matrix of coefficients into the product of a lower triangular matrix and an orthogonal matrix. We show how the system of linear equations can be decomposed into a collection of smaller independent problems that can then be used to construct an iterative method for a system of smaller dimensionality. We show that the conditioning of the reduced problem cannot be worse than that of the original, unlike Schur complement methods in the non-symmetric case. The paradigm depends on the existence of an ordering of the rows representing the equations into blocks of rows that are mutually structurally orthogonal, except for a last block row that is coupled to all other rows in a limited way.

Original languageEnglish (US)
Pages (from-to)491-503
Number of pages13
JournalNumerical Linear Algebra with Applications
Issue number7-8
StatePublished - 2000


  • Orthogonal factorization
  • Schur complement
  • Sparse matrix equations


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