DORMTR(3F)DORMTR(3F)NAME
DORMTR - overwrite the general real M-by-N matrix C with SIDE = 'L'
SIDE = 'R' TRANS = 'N'
SYNOPSIS
SUBROUTINE DORMTR( SIDE, UPLO, TRANS, M, N, A, LDA, TAU, C, LDC, WORK,
LWORK, INFO )
CHARACTER SIDE, TRANS, UPLO
INTEGER INFO, LDA, LDC, LWORK, M, N
DOUBLE PRECISION A( LDA, * ), C( LDC, * ), TAU( * ), WORK(
LWORK )
PURPOSE
DORMTR 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 of order nq, with nq = m if SIDE =
'L' and nq = n if SIDE = 'R'. Q is defined as the product of nq-1
elementary reflectors, as returned by DSYTRD:
if UPLO = 'U', Q = H(nq-1) . . . H(2)H(1);
if UPLO = 'L', Q = H(1)H(2) . . . H(nq-1).
ARGUMENTS
SIDE (input) CHARACTER*1
= 'L': apply Q or Q**T from the Left;
= 'R': apply Q or Q**T from the Right.
UPLO (input) CHARACTER*1
= 'U': Upper triangle of A contains elementary reflectors from
DSYTRD; = 'L': Lower triangle of A contains elementary reflectors
from DSYTRD.
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.
A (input) DOUBLE PRECISION array, dimension
(LDA,M) if SIDE = 'L' (LDA,N) if SIDE = 'R' The vectors which
define the elementary reflectors, as returned by DSYTRD.
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DORMTR(3F)DORMTR(3F)
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,M) if SIDE =
'L'; LDA >= max(1,N) if SIDE = 'R'.
TAU (input) DOUBLE PRECISION array, dimension
(M-1) if SIDE = 'L' (N-1) if SIDE = 'R' TAU(i) must contain the
scalar factor of the elementary reflector H(i), as returned by
DSYTRD.
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
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