LAPACK  3.5.0
LAPACK: Linear Algebra PACKage
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dhst01.f File Reference

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Functions/Subroutines

subroutine dhst01 (N, ILO, IHI, A, LDA, H, LDH, Q, LDQ, WORK, LWORK, RESULT)
 DHST01 More...
 

Function/Subroutine Documentation

subroutine dhst01 ( integer  N,
integer  ILO,
integer  IHI,
double precision, dimension( lda, * )  A,
integer  LDA,
double precision, dimension( ldh, * )  H,
integer  LDH,
double precision, dimension( ldq, * )  Q,
integer  LDQ,
double precision, dimension( lwork )  WORK,
integer  LWORK,
double precision, dimension( 2 )  RESULT 
)

DHST01

Purpose:
 DHST01 tests the reduction of a general matrix A to upper Hessenberg
 form:  A = Q*H*Q'.  Two test ratios are computed;

 RESULT(1) = norm( A - Q*H*Q' ) / ( norm(A) * N * EPS )
 RESULT(2) = norm( I - Q'*Q ) / ( N * EPS )

 The matrix Q is assumed to be given explicitly as it would be
 following DGEHRD + DORGHR.

 In this version, ILO and IHI are not used and are assumed to be 1 and
 N, respectively.
Parameters
[in]N
          N is INTEGER
          The order of the matrix A.  N >= 0.
[in]ILO
          ILO is INTEGER
[in]IHI
          IHI is INTEGER

          A is assumed to be upper triangular in rows and columns
          1:ILO-1 and IHI+1:N, so Q differs from the identity only in
          rows and columns ILO+1:IHI.
[in]A
          A is DOUBLE PRECISION array, dimension (LDA,N)
          The original n by n matrix A.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).
[in]H
          H is DOUBLE PRECISION array, dimension (LDH,N)
          The upper Hessenberg matrix H from the reduction A = Q*H*Q'
          as computed by DGEHRD.  H is assumed to be zero below the
          first subdiagonal.
[in]LDH
          LDH is INTEGER
          The leading dimension of the array H.  LDH >= max(1,N).
[in]Q
          Q is DOUBLE PRECISION array, dimension (LDQ,N)
          The orthogonal matrix Q from the reduction A = Q*H*Q' as
          computed by DGEHRD + DORGHR.
[in]LDQ
          LDQ is INTEGER
          The leading dimension of the array Q.  LDQ >= max(1,N).
[out]WORK
          WORK is DOUBLE PRECISION array, dimension (LWORK)
[in]LWORK
          LWORK is INTEGER
          The length of the array WORK.  LWORK >= 2*N*N.
[out]RESULT
          RESULT is DOUBLE PRECISION array, dimension (2)
          RESULT(1) = norm( A - Q*H*Q' ) / ( norm(A) * N * EPS )
          RESULT(2) = norm( I - Q'*Q ) / ( N * EPS )
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
November 2011

Definition at line 134 of file dhst01.f.

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