_QZHES(3F)_QZHES(3F)NAME
QZHES, SQZHES - EISPACK routine. This subroutine is the first step of
the QZ algorithm for solving generalized matrix eigenvalue problems.
SYNOPSYS
subroutine qzhes(nm, n, a, b, matz, z)
integer nm, n
double precision a(nm,n), b(nm,n), z(nm,n)
logical matz
subroutine sqzhes(nm, n, a, b, matz, z)
integer nm, n
real a(nm,n), b(nm,n), z(nm,n)
logical matz
DESCRIPTION
This subroutine accepts a pair of REAL GENERAL matrices and reduces one
of them to upper Hessenberg form and the other to upper triangular form
using orthogonal transformations. It is usually followed by QZIT,
QZVAL and, possibly, QZVEC.
On Input
NM must be set to the row dimension of two-dimensional array parameters
as declared in the calling program dimension statement.
N is the order of the matrices.
A contains a real general matrix.
B contains a real general matrix.
MATZ should be set to .TRUE. if the right hand transformations are to be
accumulated for later use in computing eigenvectors, and to .FALSE.
otherwise. On Output
A has been reduced to upper Hessenberg form. The elements below the
first subdiagonal have been set to zero.
B has been reduced to upper triangular form. The elements below the main
diagonal have been set to zero.
Z contains the product of the right hand transformations if MATZ has been
set to .TRUE. Otherwise, Z is not referenced. Questions and comments
should be directed to B. S. Garbow, APPLIED MATHEMATICS DIVISION, ARGONNE
NATIONAL LABORATORY
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