SRC/dorm2r.f(3)

NAME
SRC/dorm2r.f

SYNOPSIS

  Functions/Subroutines
subroutine dorm2r (side, trans, m, n, k, a, lda, tau, c, ldc, work, info)
DORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf (unblocked algorithm).

Function/Subroutine Documentation

  subroutine dorm2r (character side, character trans, integer m, integer n, integer k, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( * ) tau, double precision, dimension( ldc, * ) c, integer ldc, double precision, dimension( * ) work, integer info)

DORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf (unblocked algorithm).

Purpose:

     DORM2R overwrites the general real m by n matrix C with
           Q * C  if SIDE = 'L' and TRANS = 'N', or
           Q**T* C  if SIDE = 'L' and TRANS = 'T', or
           C * Q  if SIDE = 'R' and TRANS = 'N', or
           C * Q**T if SIDE = 'R' and TRANS = 'T',
     where Q is a real orthogonal matrix defined as the product of k
     elementary reflectors
           Q = H(1) H(2) . . . H(k)
     as returned by DGEQRF. 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': apply Q  (No transpose)
              = 'T': apply Q**T (Transpose)

    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.

    A

              A is DOUBLE PRECISION array, dimension (LDA,K)
              The i-th column must contain the vector which defines the
              elementary reflector H(i), for i = 1,2,...,k, as returned by
              DGEQRF in the first k columns of its array argument A.
              A is modified by the routine but restored on exit.

    LDA

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

    TAU

              TAU is DOUBLE PRECISION array, dimension (K)
              TAU(i) must contain the scalar factor of the elementary
              reflector H(i), as returned by DGEQRF.

    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
                                       (N) if SIDE = 'L',
                                       (M) 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 157 of file dorm2r.f.

Author

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