SRC/sgemqrt.f(3)

NAME
SRC/sgemqrt.f

SYNOPSIS

  Functions/Subroutines
subroutine sgemqrt (side, trans, m, n, k, nb, v, ldv, t, ldt, c, ldc, work, info)
SGEMQRT

Function/Subroutine Documentation

  subroutine sgemqrt (character side, character trans, integer m, integer n, integer k, integer nb, real, dimension( ldv, * ) v, integer ldv, real, dimension( ldt, * ) t, integer ldt, real, dimension( ldc, * ) c, integer ldc, real, dimension( * ) work, integer info)

SGEMQRT

Purpose:

    !>
    !> SGEMQRT 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 defined as the product of K
    !> elementary reflectors:
    !>
    !>       Q = H(1) H(2) . . . H(K) = I - V T V**T
    !>
    !> generated using the compact WY representation as returned by SGEQRT.
    !>
    !> Q is of order M if SIDE = 'L' and of order N  if SIDE = 'R'.
    !>

Parameters
    SIDE

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

    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.
    !>

    K

    !>          K is INTEGER
    !>          The number of elementary reflectors whose product defines
    !>          the matrix Q.
    !>          If SIDE = 'L', M >= K >= 0;
    !>          if SIDE = 'R', N >= K >= 0.
    !>

    NB

    !>          NB is INTEGER
    !>          The block size used for the storage of T.  K >= NB >= 1.
    !>          This must be the same value of NB used to generate T
    !>          in SGEQRT.
    !>

    V

    !>          V is REAL array, dimension (LDV,K)
    !>          The i-th column must contain the vector which defines the
    !>          elementary reflector H(i), for i = 1,2,...,k, as returned by
    !>          SGEQRT in the first K columns of its array argument A.
    !>

    LDV

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

    T

    !>          T is REAL array, dimension (LDT,K)
    !>          The upper triangular factors of the block reflectors
    !>          as returned by SGEQRT, stored as a NB-by-N matrix.
    !>

    LDT

    !>          LDT is INTEGER
    !>          The leading dimension of the array T.  LDT >= NB.
    !>

    C

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

    LDC

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

    WORK

    !>          WORK is REAL array. The dimension of WORK is
    !>           N*NB if SIDE = 'L', or  M*NB if SIDE = 'R'.
    !>

    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 166 of file sgemqrt.f.

Author

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