subroutine cungqr (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGQR
CUNGQR
Purpose:
CUNGQR generates an M-by-N complex matrix Q with orthonormal columns, which is defined as the first N columns of a product of K elementary reflectors of order M Q = H(1) H(2) . . . H(k) as returned by CGEQRF.
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. M >= N >= 0.
K
K is INTEGER The number of elementary reflectors whose product defines the matrix Q. N >= K >= 0.
A
A is COMPLEX array, dimension (LDA,N) On entry, the i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by CGEQRF in the first k columns 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 COMPLEX array, dimension (K) TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGEQRF.
WORK
WORK is COMPLEX 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,N). For optimum performance LWORK >= N*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 cungqr.f.
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