DOPMTR - overwrite the general real M-by-N matrix C with
SIDE = 'L' SIDE = 'R' TRANS = 'N'
SYNOPSIS
SUBROUTINE DOPMTR( SIDE, UPLO, TRANS, M, N, AP, TAU, C,
LDC, WORK, INFO )
CHARACTER SIDE, TRANS, UPLO
INTEGER INFO, LDC, M, N
DOUBLE PRECISION AP( * ), C( LDC, * ), TAU( *
), WORK( * )
PURPOSE
DOPMTR 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 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
DSPTRD using packed storage:
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 triangular packed storage used in
previous call to DSPTRD; = 'L': Lower triangular
packed storage used in previous call to DSPTRD.
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.
AP (input) DOUBLE PRECISION array, dimension
(M*(M+1)/2) if SIDE = 'L' (N*(N+1)/2) if SIDE =
'R' The vectors which define the elementary
reflectors, as returned by DSPTRD. AP is modified
TAU (input) DOUBLE PRECISION array, dimension (M-1) if
SIDE = 'L'
or (N-1) if SIDE = 'R' TAU(i) must contain the
scalar factor of the elementary reflector H(i), as
returned by DSPTRD.
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
(N) if SIDE = 'L' (M) if SIDE = 'R'
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
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