dormtr.f (3) Linux Manual Page
dormtr.f –
Synopsis
Functions/Subroutines
subroutine dormtr (SIDE, UPLO, TRANS, M, N, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)DORMTR
Function/Subroutine Documentation
subroutine dormtr (characterSIDE, characterUPLO, characterTRANS, integerM, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK, integerLWORK, integerINFO)
DORMTR Purpose:
DORMTR overwrites the general real M-by-N matrix C with
SIDE = ‘L’ SIDE = ‘R’
TRANS = ‘N’: Q * C C * Q
TRANS = ‘T’: Q**T * C C * Q**T
where Q is a real orthogonal matrix of order nq, with nq = m if
SIDE = ‘L’ and nq = n if SIDE = ‘R’. Q is defined as the product of
nq-1 elementary reflectors, as returned by DSYTRD:
if UPLO = ‘U’, Q = H(nq-1) . . . H(2) H(1);
if UPLO = ‘L’, Q = H(1) H(2) . . . H(nq-1).
Parameters:
- SIDE
SIDE is CHARACTER*1
UPLO
= ‘L’: apply Q or Q**T from the Left;
= ‘R’: apply Q or Q**T from the Right.UPLO is CHARACTER*1
TRANS
= ‘U’: Upper triangle of A contains elementary reflectors
from DSYTRD;
= ‘L’: Lower triangle of A contains elementary reflectors
from DSYTRD.TRANS is CHARACTER*1
M
= ‘N’: No transpose, apply Q;
= ‘T’: Transpose, apply Q**T.M is INTEGER
N
The number of rows of the matrix C. M >= 0.N is INTEGER
A
The number of columns of the matrix C. N >= 0.A is DOUBLE PRECISION array, dimension
LDA
(LDA,M) if SIDE = ‘L’
(LDA,N) if SIDE = ‘R’
The vectors which define the elementary reflectors, as
returned by DSYTRD.LDA is INTEGER
TAU
The leading dimension of the array A.
LDA >= max(1,M) if SIDE = ‘L’; LDA >= max(1,N) if SIDE = ‘R’.TAU is DOUBLE PRECISION array, dimension
C
(M-1) if SIDE = ‘L’
(N-1) if SIDE = ‘R’
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by DSYTRD.C is DOUBLE PRECISION array, dimension (LDC,N)
LDC
On entry, the M-by-N matrix C.
On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.LDC is INTEGER
WORK
The leading dimension of the array C. LDC >= max(1,M).WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
LWORK
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.LWORK is INTEGER
INFO
The dimension of the array WORK.
If SIDE = ‘L’, LWORK >= max(1,N);
if SIDE = ‘R’, LWORK >= max(1,M).
For optimum performance LWORK >= N*NB if SIDE = ‘L’, and
LWORK >= M*NB if SIDE = ‘R’, where NB is the optimal
blocksize.
If LWORK = -1, then a workspace query is assumed; the routine
only calculates the optimal size of the WORK array, returns
this value as the first entry of the WORK array, and no error
message related to LWORK is issued by XERBLA.INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
Author:
- Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
- November 2011
Definition at line 171 of file dormtr.f.