TESTING/EIG/dbdt01.f(3)

NAME
TESTING/EIG/dbdt01.f

SYNOPSIS

  Functions/Subroutines
subroutine dbdt01 (m, n, kd, a, lda, q, ldq, d, e, pt, ldpt, work, resid)
DBDT01

Function/Subroutine Documentation

  subroutine dbdt01 (integer m, integer n, integer kd, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldq, * ) q, integer ldq, double precision, dimension( * ) d, double precision, dimension( * ) e, double precision, dimension( ldpt, * ) pt, integer ldpt, double precision, dimension( * ) work, double precision resid)

DBDT01

Purpose:

    !>
    !> DBDT01 reconstructs a general matrix A from its bidiagonal form
    !>    A = Q * B * P**T
    !> where Q (m by min(m,n)) and P**T (min(m,n) by n) are orthogonal
    !> matrices and B is bidiagonal.
    !>
    !> The test ratio to test the reduction is
    !>    RESID = norm(A - Q * B * P**T) / ( n * norm(A) * EPS )
    !> where EPS is the machine precision.
    !>

Parameters
    M

    !>          M is INTEGER
    !>          The number of rows of the matrices A and Q.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrices A and P**T.
    !>

    KD

    !>          KD is INTEGER
    !>          If KD = 0, B is diagonal and the array E is not referenced.
    !>          If KD = 1, the reduction was performed by xGEBRD; B is upper
    !>          bidiagonal if M >= N, and lower bidiagonal if M < N.
    !>          If KD = -1, the reduction was performed by xGBBRD; B is
    !>          always upper bidiagonal.
    !>

    A

    !>          A is DOUBLE PRECISION array, dimension (LDA,N)
    !>          The m by n matrix A.
    !>

    LDA

    !>          LDA is INTEGER
    !>          The leading dimension of the array A.  LDA >= max(1,M).
    !>

    Q

    !>          Q is DOUBLE PRECISION array, dimension (LDQ,N)
    !>          The m by min(m,n) orthogonal matrix Q in the reduction
    !>          A = Q * B * P**T.
    !>

    LDQ

    !>          LDQ is INTEGER
    !>          The leading dimension of the array Q.  LDQ >= max(1,M).
    !>

    D

    !>          D is DOUBLE PRECISION array, dimension (min(M,N))
    !>          The diagonal elements of the bidiagonal matrix B.
    !>

    E

    !>          E is DOUBLE PRECISION array, dimension (min(M,N)-1)
    !>          The superdiagonal elements of the bidiagonal matrix B if
    !>          m >= n, or the subdiagonal elements of B if m < n.
    !>

    PT

    !>          PT is DOUBLE PRECISION array, dimension (LDPT,N)
    !>          The min(m,n) by n orthogonal matrix P**T in the reduction
    !>          A = Q * B * P**T.
    !>

    LDPT

    !>          LDPT is INTEGER
    !>          The leading dimension of the array PT.
    !>          LDPT >= max(1,min(M,N)).
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (M+N)
    !>

    RESID

    !>          RESID is DOUBLE PRECISION
    !>          The test ratio:
    !>          norm(A - Q * B * P**T) / ( n * norm(A) * EPS )
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 139 of file dbdt01.f.

Author

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