dgemqrt-f(3)

dgemqrt.f –

Synopsis

Functions/Subroutines

subroutine dgemqrt (SIDE, TRANS, M, N, K, NB, V, LDV, T, LDT, C, LDC, WORK, INFO)
DGEMQRT

Function/Subroutine Documentation

subroutine dgemqrt (characterSIDE, characterTRANS, integerM, integerN, integerK, integerNB, double precision, dimension( ldv, * )V, integerLDV, double precision, dimension( ldt, * )T, integerLDT, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK, integerINFO)

DGEMQRT

Purpose:

 DGEMQRT 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) = I - V T V**T
 generated using the compact WY representation as returned by DGEQRT. 
 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;
 = 'C': Transpose, apply Q**T.

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

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

 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.

 NB is INTEGER
 The block size used for the storage of T. K >= NB >= 1.
 This must be the same value of NB used to generate T
 in CGEQRT.

 V is DOUBLE PRECISION array, dimension (LDV,K)
 The i-th column must contain the vector which defines the
 elementary reflector H(i), for i = 1,2,...,k, as returned by
 CGEQRT in the first K columns of its array argument A.

LDV

 LDV is INTEGER
 The leading dimension of the array V.
 If SIDE = 'L', LDA >= max(1,M);
 if SIDE = 'R', LDA >= max(1,N).

 T is DOUBLE PRECISION array, dimension (LDT,K)
 The upper triangular factors of the block reflectors
 as returned by CGEQRT, stored as a NB-by-N matrix.

LDT

 LDT is INTEGER
 The leading dimension of the array T. LDT >= NB.

 C is DOUBLE PRECISION array, dimension (LDC,N)
 On entry, the M-by-N matrix C.
 On exit, C is overwritten by Q C, Q**T C, 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. The dimension of
 WORK is N*NB if SIDE = 'L', or M*NB if SIDE = 'R'.

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 168 of file dgemqrt.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.