LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ dlarzb()

subroutine dlarzb ( character side,
character trans,
character direct,
character storev,
integer m,
integer n,
integer k,
integer l,
double precision, dimension( ldv, * ) v,
integer ldv,
double precision, dimension( ldt, * ) t,
integer ldt,
double precision, dimension( ldc, * ) c,
integer ldc,
double precision, dimension( ldwork, * ) work,
integer ldwork )

DLARZB applies a block reflector or its transpose to a general matrix.

Download DLARZB + dependencies [TGZ] [ZIP] [TXT]

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.
!>
Parameters
[in]SIDE
!>          SIDE is CHARACTER*1
!>          = 'L': apply H or H**T from the Left
!>          = 'R': apply H or H**T from the Right
!>
[in]TRANS
!>          TRANS is CHARACTER*1
!>          = 'N': apply H (No transpose)
!>          = 'C': apply H**T (Transpose)
!>
[in]DIRECT
!>          DIRECT is 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)
!>
[in]STOREV
!>          STOREV is CHARACTER*1
!>          Indicates how the vectors which define the elementary
!>          reflectors are stored:
!>          = 'C': Columnwise                        (not supported yet)
!>          = 'R': Rowwise
!>
[in]M
!>          M is INTEGER
!>          The number of rows of the matrix C.
!>
[in]N
!>          N is INTEGER
!>          The number of columns of the matrix C.
!>
[in]K
!>          K is INTEGER
!>          The order of the matrix T (= the number of elementary
!>          reflectors whose product defines the block reflector).
!>
[in]L
!>          L is 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.
!>
[in]V
!>          V is DOUBLE PRECISION array, dimension (LDV,NV).
!>          If STOREV = 'C', NV = K; if STOREV = 'R', NV = L.
!>
[in]LDV
!>          LDV is INTEGER
!>          The leading dimension of the array V.
!>          If STOREV = 'C', LDV >= L; if STOREV = 'R', LDV >= K.
!>
[in]T
!>          T is DOUBLE PRECISION array, dimension (LDT,K)
!>          The triangular K-by-K matrix T in the representation of the
!>          block reflector.
!>
[in]LDT
!>          LDT is INTEGER
!>          The leading dimension of the array T. LDT >= K.
!>
[in,out]C
!>          C is DOUBLE PRECISION array, dimension (LDC,N)
!>          On entry, the M-by-N matrix C.
!>          On exit, C is overwritten by H*C or H**T*C or C*H or C*H**T.
!>
[in]LDC
!>          LDC is INTEGER
!>          The leading dimension of the array C. LDC >= max(1,M).
!>
[out]WORK
!>          WORK is DOUBLE PRECISION array, dimension (LDWORK,K)
!>
[in]LDWORK
!>          LDWORK is INTEGER
!>          The leading dimension of the array WORK.
!>          If SIDE = 'L', LDWORK >= max(1,N);
!>          if SIDE = 'R', LDWORK >= max(1,M).
!>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA
Further Details:
!>