A Stable Divide and Conquer Algorithm for the Unitary Eigenproblem

  • Authors:
  • Ming Gu;Robert Guzzo;Xue-bin Chi;Xing-Qin Cao

  • Affiliations:
  • -;-;-;-

  • Venue:
  • SIAM Journal on Matrix Analysis and Applications
  • Year:
  • 2003

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Abstract

We present a divide and conquer algorithm for computing the eigendecomposition of a unitary upper Hessenberg matrix H. Previous divide and conquer approaches suffer a potential loss of orthogonality among the computed eigenvectors of H. Using a backward stable method based on previous work by Gu and Eisenstat in the rank-one modification of the symmetric eigenproblem, our algorithm provides a backward stable method for computing the eigenvectors. The method also compares well against the efficiency of other available methods.