subroutine dorgrq (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
DORGRQ
DORGRQ
Purpose:
DORGRQ generates an M-by-N real matrix Q with orthonormal rows, which is defined as the last M rows of a product of K elementary reflectors of order N Q = H(1) H(2) . . . H(k) as returned by DGERQF.
Parameters:
M is INTEGER The number of rows of the matrix Q. M >= 0.
N
N is INTEGER The number of columns of the matrix Q. N >= M.
K
K is INTEGER The number of elementary reflectors whose product defines the matrix Q. M >= K >= 0.
A
A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the (m-k+i)-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGERQF in the last k rows of its array argument A. On exit, the M-by-N matrix Q.
LDA
LDA is INTEGER The first dimension of the array A. LDA >= max(1,M).
TAU
TAU is DOUBLE PRECISION array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGERQF.
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. LWORK >= max(1,M). For optimum performance LWORK >= M*NB, 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 has an illegal value
Author:
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 130 of file dorgrq.f.
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