dlarfb(3)

NAME

DLARFB - 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  DLARFB(  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
    DOUBLE         PRECISION C( LDC, * ), T( LDT, * ),  V(
LDV, * ), WORK( LDWORK, * )

PURPOSE

DLARFB 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 ele

mentary 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 elemen

tary 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 elemen

tary reflectors whose product defines the block reflector).

V (input) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension (LDT,K)

The triangular k by k matrix T in the representa

tion of the block reflector.

LDT (input) INTEGER

The leading dimension of the array T. LDT >= K.

C (input/output) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension (LD

WORK,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).

LAPACK version 3.0 15 June 2000

DLARFB(3)