P?GEQRF

Calculate the QR factorization of a matrix, that is, .

Interface Definition

C interface:

void psgeqrf_(const int *m, const int *n, float*a, const int *ia, const int *ja, const int *desca, float*tau, float*work, int *lwork, int *info)

void pdgeqrf_(const int *m, const int *n, double *a, const int *ia, const int *ja, const int *desca, double *tau, double *work, int *lwork, int *info)

void pcgeqrf_(const int *m, const int *n, float _Complex *a, const int *ia, const int *ja, const int *desca, float _Complex *tau, float _Complex *work, int *lwork, int *info)

void pzgeqrf_(const int *m, const int *n, double _Complex *a, const int *ia, const int *ja, const int *desca, double _Complex *tau, double _Complex *work, int *lwork, int *info)

Fortran interface:

PSGEQRF(m, n, a, ia, ja, desca, tau, work, lwork, info)

PDGEQRF(m, n, a, ia, ja, desca, tau, work, lwork, info)

PCGEQRF(m, n, a, ia, ja, desca, tau, work, lwork, info)

PZGEQRF(m, n, a, ia, ja, desca, tau, work, lwork, info)

Parameters

Parameter	Type	Scope	Description	Input/Output
m	Integer	Global	Number of rows to be operated, for example, the number of rows in a submatrix	Input
n	Integer	Global	Number of columns to be operated, for example, the number of columns in a submatrix	Input
a	A single-precision floating-point array for psgeqrf A double-precision floating-point array for pdgeqrf A single-precision complex number array for pcgeqrf A double-precision complex number array for pzgeqrf	Local	Stores matrix A to be factorized before calling this function. After this function is called, a matrix R with a size of min(m,n)n* (when m ≥ n, R is an upper triangular matrix) is stored on and above the diagonal. Elements below the diagonal and tau jointly represent an orthogonal matrix Q.	Input/Output
ia	Integer	Global	Row indices of the submatrix in the global matrix	Input
ja	Integer	Global	Column indices of the submatrix in the global matrix	Input
desca	Integer array	Local and global	Descriptor of distributed matrix A	Input
tau	A single-precision floating-point array for psgeqrf A double-precision floating-point array for pdgeqrf A single-precision complex number array for pcgeqrf A double-precision complex number array for pzgeqrf	Local	Elementary reflection coefficient. Its length is min(m, n).	Output
work	A single-precision floating-point array for psgeqrf A double-precision floating-point array for pdgeqrf A single-precision complex number array for pcgeqrf A double-precision complex number array for pzgeqrf	Local	Temporary storage space. When you exit, the minimum and optimal lwork values are returned.	Output
lwork	Integer	Local and global	Dimension of the work array	Input
info	Integer	Global	Execution result: 0: The execution is successful. Smaller than 0: The value of the -info-th parameter is invalid.	Output

Dependencies

#include <kscalapack.h>

#include <kscalapack_utils.h>

#include <kml_service.h>

Examples

    int m = 8;
    int n = 8;       
    int nprow = 2;   
    int npcol = 2;
    int mb = 4;:q   
    int nb = 4;          
    np = 4;
    int descA[9];
    int info;
    int ipiv[10] = {0};
    int lddA = mpA > 1 ? mpA : 1;
    descinit_( descA,  &n, &n, &nb, &nb, &izero, &izero, &ictxt, &lddA, &info);

    double tau[8];
    int lwork = 48;
    double work[48];
    
    np = 4;
    /* 
     * Origin A: 
    /*  
    4.50000 11.0000 17.0000 8.00000 11.0000 11.0000 17.0000 8.00000
    14.0000 8.50000 9.00000 17.0000 14.0000 13.0000 9.00000 17.0000
    15.0000 14.0000 7.50000 11.0000 15.0000 14.0000 10.0000 11.0000
    13.0000 10.0000 15.0000 13.5000 13.0000 10.0000 15.0000 14.0000
    11.0000 11.0000 17.0000 8.00000 4.50000 11.0000 17.0000 8.00000
    14.0000 13.0000 9.00000 17.0000 14.0000 8.50000 9.00000 17.0000
    15.0000 14.0000 10.0000 11.0000 15.0000 14.0000 7.50000 11.0000
    13.0000 10.0000 15.0000 14.0000 13.0000 10.0000 15.0000 13.5000
    */
    /* Query optimal work size */ 
    pdgeqrf_(&n, &n, A,  &ione, &ione, descA, tau, work, &lwork, &info);
    * After PDGEQRF: 
    /*
    -36.3490 -31.6790 -32.1329 -35.4205 -35.1867 -31.6790 -32.1329 -35.4205
    0.342726 8.46706 11.1681 0.285094 4.34884 6.07544 11.1681 0.285094
    0.367206 0.114565 13.7477 3.02971 -0.816048 1.94287 13.2930 3.02971
    0.318245 0.245466 -0.182222 7.89794 5.36891 -0.658967 0.174397 7.86629
    0.269284 0.0337660 -0.199487 0.530335 5.89453 2.63366 -0.221784 0.0288312
    0.342726 0.111495 0.258678 -0.396869 0.304197 4.86159 0.325469 -0.0199092
    0.367206 0.114565 0.265211 0.293751 -0.0482493 -0.0280641 3.47962 0.00528634
    0.318245 0.245466 -0.182222 0.173244 -0.0665625 0.227001 -0.112593 -0.705509
    */

Parent topic: Matrix Factorization