How much can we speedup Gaussian elimination with pivoting?

  • Authors:
  • M. Leoncini

  • Affiliations:
  • Univ. di Pisa, Pisa, Italy

  • Venue:
  • SPAA '94 Proceedings of the sixth annual ACM symposium on Parallel algorithms and architectures
  • Year:
  • 1994

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Abstract

Consider the problem of determining the pivot sequence used by the Gaussian Elimination algorithm with Partial Pivoting (GEPP). Let N stand for the order of the input matrix and let &egr; be any positive constant. Assuming P ≠ NC, we prove that if GEPP were decidable in parallel time M1/2–&egr; then all the problems in P would be characterized by polynomial speedup. This strengthens the P-completeness result that holds of GEPP. We conjecture that our result is valid even with the exponent 1 replaced for 1/2, and provide supporting arguments based on our result. This latter improvement would demonstrate the optimality of the naive parallel algorithm for GEPP (modulo P ≠ NC).