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cungql.f(3) LAPACK cungql.f(3)

NAME

cungql.f

SYNOPSIS

Functions/Subroutines


subroutine cungql (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGQL

Function/Subroutine Documentation

subroutine cungql (integer M, integer N, integer K, complex, dimension( lda, * ) A, integer LDA, complex, dimension( * ) TAU, complex, dimension( * ) WORK, integer LWORK, integer INFO)

CUNGQL

Purpose:


CUNGQL generates an M-by-N complex matrix Q with orthonormal columns,
which is defined as the last N columns of a product of K elementary
reflectors of order M
Q = H(k) . . . H(2) H(1)
as returned by CGEQLF.

Parameters:

M


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 (n-k+i)-th column must contain the vector which
defines the elementary reflector H(i), for i = 1,2,...,k, as
returned by CGEQLF in the last 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 CGEQLF.

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 Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

December 2016

Definition at line 130 of file cungql.f.

Author

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Tue Nov 14 2017 Version 3.8.0