SORM2R(1) LAPACK routine (version 3.2) SORM2R(1)NAME
SORM2R - overwrites the general real m by n matrix C with Q * C if
SIDE = 'L' and TRANS = 'N', or Q'* C if SIDE = 'L' and TRANS = 'T',
or C * Q if SIDE = 'R' and TRANS = 'N', or C * Q' if SIDE = 'R' and
TRANS = 'T',
SYNOPSIS
SUBROUTINE SORM2R( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK,
INFO )
CHARACTER SIDE, TRANS
INTEGER INFO, K, LDA, LDC, M, N
REAL A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
PURPOSE
SORM2R overwrites the general real m by n matrix C with where Q is a
real orthogonal matrix defined as the product of k elementary reflec‐
tors
Q = H(1)H(2) . . . H(k)
as returned by SGEQRF. 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' from the Left
= 'R': apply Q or Q' from the Right
TRANS (input) CHARACTER*1
= 'N': apply Q (No transpose)
= 'T': apply Q' (Transpose)
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) REAL array, dimension (LDA,K)
The i-th column must contain the vector which defines the ele‐
mentary reflector H(i), for i = 1,2,...,k, as returned by SGE‐
QRF in the first k columns of its array argument A. A is modi‐
fied 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) REAL array, dimension (K)
TAU(i) must contain the scalar factor of the elementary reflec‐
tor H(i), as returned by SGEQRF.
C (input/output) REAL array, dimension (LDC,N)
On entry, the m by n matrix C. On exit, C is overwritten by
Q*C or Q'*C or C*Q' or C*Q.
LDC (input) INTEGER
The leading dimension of the array C. LDC >= max(1,M).
WORK (workspace) REAL 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 illegal value
LAPACK routine (version 3.2) November 2008 SORM2R(1)
