p?unglq

Generates the unitary matrix Q of the LQ factorization formed by p?gelqf.

Syntax

Fortran:

call pcunglq(m, n, k, a, ia, ja, desca, tau, work, lwork, info)

call pzunglq(m, n, k, a, ia, ja, desca, tau, work, lwork, info)

C:

void pcunglq (MKL_INT *m , MKL_INT *n , MKL_INT *k , MKL_Complex8 *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_Complex8 *tau , MKL_Complex8 *work , MKL_INT *lwork , MKL_INT *info );

void pzunglq (MKL_INT *m , MKL_INT *n , MKL_INT *k , MKL_Complex16 *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , MKL_Complex16 *tau , MKL_Complex16 *work , MKL_INT *lwork , MKL_INT *info );

Include Files

  • C: mkl_scalapack.h

Description

This routine generates the whole or part of m-by-n complex distributed matrix Q denoting A(ia:ia+m-1, ja:ja+n-1) with orthonormal rows, which is defined as the first m rows of a product of k elementary reflectors of order n

Q = (H(k))H...*(H(2))H*(H(1))H as returned by p?gelqf.

Input Parameters

m

(global) INTEGER. The number of rows in the submatrix sub(Q) (m0).

n

(global) INTEGER. The number of columns in the submatrix sub(Q) (nm0).

k

(global) INTEGER. The number of elementary reflectors whose product defines the matrix Q (mk0).

a

(local)

COMPLEX for pcunglq

DOUBLE COMPLEX for pzunglq

Pointer into the local memory to an array of local dimension (lld_a, LOCc(ja+n-1)). On entry, the i-th row must contain the vector which defines the elementary reflector H(i), iaiia+k-1, as returned by p?gelqf in the k rows of its distributed matrix argument A(ia:ia+k-1, ja:*).

ia, ja

(global) INTEGER. The row and column indices in the global array a indicating the first row and the first column of the submatrix A(ia:ia+m-1,ja:ja+n-1), respectively.

desca

(global and local) INTEGER array, dimension (dlen_). The array descriptor for the distributed matrix A.

tau

(local)

COMPLEX for pcunglq

DOUBLE COMPLEX for pzunglq

Array, size LOCr(ia+k-1).

Contains the scalar factors tau of elementary reflectors H(i). tau is tied to the distributed matrix A.

work

(local)

COMPLEX for pcunglq

DOUBLE COMPLEX for pzunglq

Workspace array of dimension of lwork.

lwork

(local or global) INTEGER, dimension of work, must be at least lwork mb_a*(mpa0+nqa0+mb_a), where

iroffa = mod(ia-1, mb_a),

icoffa = mod(ja-1, nb_a),

iarow = indxg2p(ia, mb_a, MYROW, rsrc_a, NPROW),

iacol = indxg2p(ja, nb_a, MYCOL, csrc_a, NPCOL),

mpa0 = numroc(m+iroffa, mb_a, MYROW, iarow, NPROW),

nqa0 = numroc(n+icoffa, nb_a, MYCOL, iacol, NPCOL)

indxg2p and numroc are ScaLAPACK tool functions; MYROW, MYCOL, NPROW and NPCOL can be determined by calling the subroutine blacs_gridinfo.

If lwork = -1, then lwork is global input and a workspace query is assumed; the routine only calculates the minimum and optimal size for all work arrays. Each of these values is returned in the first entry of the corresponding work array, and no error message is issued by pxerbla.

Output Parameters

a

Contains the local pieces of the m-by-n distributed matrix Q to be factored.

work(1)

On exit, work(1) contains the minimum value of lwork required for optimum performance.

info

(global) INTEGER.

= 0: the execution is successful.

< 0: if the i-th argument is an array and the j-entry had an illegal value, then info = -(i*100+j), if the i-th argument is a scalar and had an illegal value, then info = -i.

For more complete information about compiler optimizations, see our Optimization Notice.