DLARZB(3S)DLARZB(3S)NAME
DLARZB - applie 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, * )
IMPLEMENTATION
These routines are part of the SCSL Scientific Library and can be loaded
using either the -lscs or the -lscs_mp option. The -lscs_mp option
directs the linker to use the multi-processor version of the library.
When linking to SCSL with -lscs or -lscs_mp, the default integer size is
4 bytes (32 bits). Another version of SCSL is available in which integers
are 8 bytes (64 bits). This version allows the user access to larger
memory sizes and helps when porting legacy Cray codes. It can be loaded
by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
only one of the two versions; 4-byte integer and 8-byte integer library
calls cannot be mixed.
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 =
'R' and DIRECT = 'B' are supported.
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)
= 'C': 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, not supported yet)
= '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 (not supported yet)
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DLARZB(3S)DLARZB(3S)
= '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).
L (input) INTEGER
The number of columns of the matrix V containing the meaningful
part of the Householder reflectors. If SIDE = 'L', M >= L >= 0,
if SIDE = 'R', N >= L >= 0.
V (input) DOUBLE PRECISION array, dimension (LDV,NV).
If STOREV = 'C', NV = K; if STOREV = 'R', NV = L.
LDV (input) INTEGER
The leading dimension of the array V. If STOREV = 'C', LDV >= L;
if STOREV = 'R', 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 H'*C or C*H or C*H'.
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 = 'L', LDWORK
>= max(1,N); if SIDE = 'R', LDWORK >= max(1,M).
FURTHER DETAILS
Based on contributions by
A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA
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DLARZB(3S)DLARZB(3S)SEE ALSOINTRO_LAPACK(3S), INTRO_SCSL(3S)
This man page is available only online.
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