dgemqrt.f(3)

NAME
dgemqrt.f

SYNOPSIS

  Functions/Subroutines
subroutine dgemqrt (SIDE, TRANS, M, N, K, NB, V, LDV, T, LDT, C, LDC, WORK, INFO)
DGEMQRT

Function/Subroutine Documentation

  subroutine dgemqrt (character SIDE, character TRANS, integer M, integer N, integer K, integer NB, double precision, dimension( ldv, * ) V, integer LDV, double precision, dimension( ldt, * ) T, integer LDT, double precision, dimension( ldc, * ) C, integer LDC, double precision, dimension( * ) WORK, integer INFO)

Purpose:

     DGEMQRT 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 DGEQRT.
     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;
              = 'C':  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 CGEQRT.

    V

              V is DOUBLE PRECISION 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
              CGEQRT 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 DOUBLE PRECISION array, dimension (LDT,K)
              The upper triangular factors of the block reflectors
              as returned by CGEQRT, stored as a NB-by-N matrix.

    LDT

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

    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, 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 DOUBLE PRECISION 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 dgemqrt.f.

Author

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