dlarzb (l) - Linux Man Pages

dlarzb: applies a real block reflector H or its transpose H**T to a real distributed M-by-N C from the left or the right

NAME

DLARZB - applies a real block reflector H or its transpose H**T to a real distributed M-by-N C from the left or the right

SYNOPSIS

SUBROUTINE DLARZB(
SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, LDV, T, LDT, C, LDC, WORK, LDWORK )

    
CHARACTER DIRECT, SIDE, STOREV, TRANS

    
INTEGER K, L, LDC, LDT, LDV, LDWORK, M, N

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

PURPOSE

DLARZB applies a real block reflector H or its transpose H**T to a real distributed M-by-N C from the left or the right. Currently, only STOREV = aqRaq and DIRECT = aqBaq are supported.

ARGUMENTS

SIDE (input) CHARACTER*1
= aqLaq: apply H or Haq from the Left
= aqRaq: apply H or Haq from the Right
TRANS (input) CHARACTER*1

= aqNaq: apply H (No transpose)
= aqCaq: apply Haq (Transpose)
DIRECT (input) CHARACTER*1
Indicates how H is formed from a product of elementary reflectors = aqFaq: H = H(1) H(2) . . . H(k) (Forward, not supported yet)
= aqBaq: H = H(k) . . . H(2) H(1) (Backward)
STOREV (input) CHARACTER*1
Indicates how the vectors which define the elementary reflectors are stored:
= aqCaq: Columnwise (not supported yet)
= aqRaq: 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).
L (input) INTEGER
The number of columns of the matrix V containing the meaningful part of the Householder reflectors. If SIDE = aqLaq, M >= L >= 0, if SIDE = aqRaq, N >= L >= 0.
V (input) DOUBLE PRECISION array, dimension (LDV,NV).
If STOREV = aqCaq, NV = K; if STOREV = aqRaq, NV = L.
LDV (input) INTEGER
The leading dimension of the array V. If STOREV = aqCaq, LDV >= L; if STOREV = aqRaq, LDV >= K.
T (input) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension (LDC,N)
On entry, the M-by-N matrix C. On exit, C is overwritten by H*C or Haq*C or C*H or C*Haq.
LDC (input) INTEGER
The leading dimension of the array C. LDC >= max(1,M).
WORK (workspace) DOUBLE PRECISION array, dimension (LDWORK,K)
LDWORK (input) INTEGER
The leading dimension of the array WORK. If SIDE = aqLaq, LDWORK >= max(1,N); if SIDE = aqRaq, LDWORK >= max(1,M).

FURTHER DETAILS

Based on contributions by

  A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA