p?org2r/p?ung2r

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 3/22/2024

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p?org2r/p?ung2r

Generates all or part of the orthogonal/unitary matrix Q from a QR factorization determined by p?geqrf (unblocked algorithm).

Syntax

void psorg2r (MKL_INT *m , MKL_INT *n , MKL_INT *k , float *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , float *tau , float *work , MKL_INT *lwork , MKL_INT *info );

void pdorg2r (MKL_INT *m , MKL_INT *n , MKL_INT *k , double *a , MKL_INT *ia , MKL_INT *ja , MKL_INT *desca , double *tau , double *work , MKL_INT *lwork , MKL_INT *info );

void pcung2r (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 pzung2r (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

mkl_scalapack.h

Description

The p?org2r/p?ung2rfunction generates an m-by-n real/complex matrix Q denoting A(ia:ia+m-1, ja:ja+n-1) 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 p?geqrf.

Input Parameters

m

(global)

The number of rows in the distributed submatrix Q.m ≥ 0.

n

(global)

The number of columns in the distributed submatrix Q. m ≥ n ≥ 0.

k

(global)

The number of elementary reflectors whose product defines the matrix Q. n ≥ k ≥ 0.

a

Pointer into the local memory to an array of sizelld_a * LOCc(ja+n-1)

On entry, the j-th column of the matrix stored in amust contain the vector that defines the elementary reflector H(j), ja ≤ j ≤ ja+k-1, as returned by p?geqrf in the k columns of its distributed matrix argument A(ia:*,ja:ja+k-1).

ia

(global)

The row index in the global matrix A indicating the first row of sub(A).

ja

(global)

The column index in the global matrix A indicating the first column of sub(A).

desca

(global and local) array of size dlen_.

The array descriptor for the distributed matrix A.

tau

(local)

Array of size LOCc(ja+k-1).

tau[j] contains the scalar factor of the elementary reflector H(j+1), j = 0, 1, ..., LOCc(ja+k-1)-1, as returned by p?geqrf. This array is tied to the distributed matrix A.

work

(local)

Workspace array of size lwork.

lwork

(local or global)

The size of the array work.

lwork is local input and must be at least lwork ≥ mpa0 + max(1, nqa0),

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 function blacs_gridinfo.

If lwork = -1, then lwork is global input and a workspace query is assumed; the function 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

On exit, this array contains the local pieces of the m-by-n distributed matrix Q.

work

On exit, work[0] returns the minimal and optimal lwork.

info

(local).

= 0: successful exit

< 0: if the i-th argument is an array and the j-th entry, indexed j-1, 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.

Parent topic: ScaLAPACK Auxiliary Routines

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Developer Reference for Intel® oneAPI Math Kernel Library for C

p?org2r/p?ung2r

Syntax

Include Files

Description

Input Parameters

Output Parameters

See Also