dormqr.f (3) Linux Manual Page

dormqr.f –

Synopsis

Functions/Subroutines

subroutine dormqr (SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
DORMQR

Function/Subroutine Documentation

subroutine dormqr (characterSIDE, characterTRANS, integerM, integerN, integerK, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK, integerLWORK, integerINFO)

DORMQR

Purpose:

 DORMQR 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 defined as the product of k

 elementary reflectors

 Q = H(1) H(2) . . . H(k)

 as returned by DGEQRF. Q is of order M if SIDE = ‘L’ and of order N

 if SIDE = ‘R’.

 

Parameters:

SIDE

 SIDE is CHARACTER*1

 = ‘L’: apply Q or Q**T from the Left;

 = ‘R’: apply Q or Q**T from the Right.

TRANS

 TRANS is CHARACTER*1

 = ‘N’: No transpose, apply Q;

 = ‘T’: Transpose, apply Q**T.

M

 M is INTEGER

 The number of rows of the matrix C. M >= 0.

N

 N is INTEGER

 The number of columns of the matrix C. N >= 0.

K

 K is INTEGER

 The number of elementary reflectors whose product defines

 the matrix Q.

 If SIDE = ‘L’, M >= K >= 0;

 if SIDE = ‘R’, N >= K >= 0.

A

 A is DOUBLE PRECISION array, dimension (LDA,K)

 The i-th column must contain the vector which defines the

 elementary reflector H(i), for i = 1,2,…,k, as returned by

 DGEQRF in the first k columns of its array argument A.

LDA

 LDA is INTEGER

 The leading dimension of the array A.

 If SIDE = ‘L’, LDA >= max(1,M);

 if SIDE = ‘R’, LDA >= max(1,N).

TAU

 TAU is DOUBLE PRECISION array, dimension (K)

 TAU(i) must contain the scalar factor of the elementary

 reflector H(i), as returned by DGEQRF.

C

 C is DOUBLE PRECISION array, dimension (LDC,N)

 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

 LDC is INTEGER

 The leading dimension of the array C. LDC >= max(1,M).

WORK

 WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))

 On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

 LWORK is INTEGER

 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

 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 169 of file dormqr.f.

Author

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