SRC/dormtr.f(3)

NAME
SRC/dormtr.f

SYNOPSIS

  Functions/Subroutines
subroutine dormtr (side, uplo, trans, m, n, a, lda, tau, c, ldc, work, lwork, info)
DORMTR

Function/Subroutine Documentation

  subroutine dormtr (character side, character uplo, character trans, integer m, integer n, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( * ) tau, double precision, dimension( ldc, * ) c, integer ldc, double precision, dimension( * ) work, integer lwork, integer info)

DORMTR

Purpose:

    !>
    !> DORMTR overwrites the general real M-by-N matrix C with
    !>
    !>                 SIDE = 'L'     SIDE = 'R'
    !> TRANS = 'N':      Q * C          C * Q
    !> TRANS = 'T':      Q**T * C       C * Q**T
    !>
    !> where Q is a real orthogonal matrix of order nq, with nq = m if
    !> SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
    !> nq-1 elementary reflectors, as returned by DSYTRD:
    !>
    !> if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
    !>
    !> if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
    !>

Parameters
    SIDE

    !>          SIDE is CHARACTER*1
    !>          = 'L': apply Q or Q**T from the Left;
    !>          = 'R': apply Q or Q**T from the Right.
    !>

    UPLO

    !>          UPLO is CHARACTER*1
    !>          = 'U': Upper triangle of A contains elementary reflectors
    !>                 from DSYTRD;
    !>          = 'L': Lower triangle of A contains elementary reflectors
    !>                 from DSYTRD.
    !>

    TRANS

    !>          TRANS is CHARACTER*1
    !>          = 'N':  No transpose, apply Q;
    !>          = 'T':  Transpose, apply Q**T.
    !>

    M

    !>          M is INTEGER
    !>          The number of rows of the matrix C. M >= 0.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix C. N >= 0.
    !>

    A

    !>          A is DOUBLE PRECISION array, dimension
    !>                               (LDA,M) if SIDE = 'L'
    !>                               (LDA,N) if SIDE = 'R'
    !>          The vectors which define the elementary reflectors, as
    !>          returned by DSYTRD.
    !>

    LDA

    !>          LDA is INTEGER
    !>          The leading dimension of the array A.
    !>          LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.
    !>

    TAU

    !>          TAU is DOUBLE PRECISION array, dimension
    !>                               (M-1) if SIDE = 'L'
    !>                               (N-1) if SIDE = 'R'
    !>          TAU(i) must contain the scalar factor of the elementary
    !>          reflector H(i), as returned by DSYTRD.
    !>

    C

    !>          C is DOUBLE PRECISION array, dimension (LDC,N)
    !>          On entry, the M-by-N matrix C.
    !>          On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
    !>

    LDC

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

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
    !>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
    !>

    LWORK

    !>          LWORK is INTEGER
    !>          The dimension of the array WORK.
    !>          If SIDE = 'L', LWORK >= max(1,N);
    !>          if SIDE = 'R', LWORK >= max(1,M).
    !>          For optimum performance LWORK >= N*NB if SIDE = 'L', and
    !>          LWORK >= M*NB if SIDE = 'R', where NB is the optimal
    !>          blocksize.
    !>
    !>          If LWORK = -1, then a workspace query is assumed; the routine
    !>          only calculates the optimal size of the WORK array, returns
    !>          this value as the first entry of the WORK array, and no error
    !>          message related to LWORK is issued by XERBLA.
    !>

    INFO

    !>          INFO is INTEGER
    !>          = 0:  successful exit
    !>          < 0:  if INFO = -i, the i-th argument had an illegal value
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 169 of file dormtr.f.

Author

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