Algorithm 590: DSUBSP and EXCHQZ: FORTRAN Subroutines for Computing Deflating Subspaces with Specified Spectrum

Received 11 November 1981; revised 2 June 1982, accepted 2 August 1982 This work was supported by the National Science Foundation under Grant ENG78-10003 and by the U.S. Air Force under Grant AFOSR-79-0094. Author's present address Philips Research Laboratory, Avenue Van Becelaere 2, Box 9, B-1170, Brussels, Belgium Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the pubhcation and its date appear, and notice is given tha t copying is by permission of the Association for Computing Machinery. To copy otherwise, or to repubhsh, requtres a fee and/or specific permission. © 1982 ACM 0098-3500/82/1200-0376 $00.75