DORMQL(l) LAPACK routine (version 1.1) DORMQL(l)
NAME
DORMQL - 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 elemen-
tary 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) 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
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value decomposition