SLARFB(3F)SLARFB(3F)NAME
SLARFB - applie a real block reflector H or its transpose H' to a real m
by n matrix C, from either the left or the right
SYNOPSIS
SUBROUTINE SLARFB( SIDE, TRANS, DIRECT, STOREV, M, N, K, V, LDV, T, LDT,
C, LDC, WORK, LDWORK )
CHARACTER DIRECT, SIDE, STOREV, TRANS
INTEGER K, LDC, LDT, LDV, LDWORK, M, N
REAL C( LDC, * ), T( LDT, * ), V( LDV, * ), WORK( LDWORK, *
)
PURPOSE
SLARFB applies a real block reflector H or its transpose H' to a real m
by n matrix C, from either the left or the right.
ARGUMENTS
SIDE (input) CHARACTER*1
= 'L': apply H or H' from the Left
= 'R': apply H or H' from the Right
TRANS (input) CHARACTER*1
= 'N': apply H (No transpose)
= 'T': apply H' (Transpose)
DIRECT (input) CHARACTER*1
Indicates how H is formed from a product of elementary reflectors
= 'F': H = H(1)H(2) . . . H(k) (Forward)
= 'B': H = H(k) . . . H(2)H(1) (Backward)
STOREV (input) CHARACTER*1
Indicates how the vectors which define the elementary reflectors
are stored:
= 'C': Columnwise
= 'R': Rowwise
M (input) INTEGER
The number of rows of the matrix C.
N (input) INTEGER
The number of columns of the matrix C.
K (input) INTEGER
The order of the matrix T (= the number of elementary reflectors
whose product defines the block reflector).
Page 1
SLARFB(3F)SLARFB(3F)
V (input) REAL array, dimension
(LDV,K) if STOREV = 'C' (LDV,M) if STOREV = 'R' and SIDE = 'L'
(LDV,N) if STOREV = 'R' and SIDE = 'R' The matrix V. See further
details.
LDV (input) INTEGER
The leading dimension of the array V. If STOREV = 'C' and SIDE =
'L', LDV >= max(1,M); if STOREV = 'C' and SIDE = 'R', LDV >=
max(1,N); if STOREV = 'R', LDV >= K.
T (input) REAL array, dimension (LDT,K)
The triangular k by k matrix T in the representation of the block
reflector.
LDT (input) INTEGER
The leading dimension of the array T. LDT >= K.
C (input/output) REAL array, dimension (LDC,N)
On entry, the m by n matrix C. On exit, C is overwritten by H*C
or H'*C or C*H or C*H'.
LDC (input) INTEGER
The leading dimension of the array C. LDA >= max(1,M).
WORK (workspace) REAL array, dimension (LDWORK,K)
LDWORK (input) INTEGER
The leading dimension of the array WORK. If SIDE = 'L', LDWORK
>= max(1,N); if SIDE = 'R', LDWORK >= max(1,M).
Page 2
