DORMQL (3lapack)

overwrite the general real M-by-N matrix C with SIDE = 'L' SIDE = 'R' TRANS = 'N'

SYNOPSIS

  SUBROUTINE DORMQL( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK,
                     INFO )

      CHARACTER      SIDE, TRANS

      INTEGER        INFO, K, LDA, LDC, LWORK, M, N

      DOUBLE         PRECISION A( LDA, * ), C( LDC, * ), TAU( * ), WORK(
                     LWORK )

PURPOSE

  DORMQL overwrites the general real M-by-N matrix C with 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(k) . . . H(2) H(1)

  as returned by DGEQLF. Q is of order M if SIDE = 'L' and of order N if SIDE
  = 'R'.

ARGUMENTS

  SIDE    (input) CHARACTER*1
          = 'L': apply Q or Q**T from the Left;
          = 'R': apply Q or Q**T from the Right.

  TRANS   (input) CHARACTER*1
          = 'N':  No transpose, apply Q;
          = 'T':  Transpose, apply Q**T.

  M       (input) INTEGER
          The number of rows of the matrix C. M >= 0.

  N       (input) INTEGER
          The number of columns of the matrix C. N >= 0.

  K       (input) 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       (input) 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 DGEQLF
          in the last k columns of its array argument A.  A is modified by
          the routine but restored on exit.

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

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

  C       (input/output) 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     (input) INTEGER
          The leading dimension of the array C. LDC >= max(1,M).

  WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

  LWORK   (input) 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.

  INFO    (output) INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value