sgeqr2 (3p)

Name

sgeqr2 - computes the QR factorization of a general rectangular matrix using an unblocked algorithm.

Synopsis

SUBROUTINE SGEQR2(M, N, A, LDA, TAU, WORK, INFO)


INTEGER INFO, LDA, M, N

REAL A(LDA,*), TAU(*), WORK(*)


SUBROUTINE SGEQR2_64(M, N, A, LDA, TAU, WORK, INFO)


INTEGER*8 INFO, LDA, M, N

REAL A(LDA,*), TAU(*), WORK(*)


F95 INTERFACE
SUBROUTINE GEQR2(M, N, A, LDA, TAU, WORK, INFO)


REAL, DIMENSION(:,:) :: A

INTEGER :: M, N, LDA, INFO

REAL, DIMENSION(:) :: TAU, WORK


SUBROUTINE GEQR2_64(M, N, A, LDA, TAU, WORK, INFO)


REAL, DIMENSION(:,:) :: A

INTEGER(8) :: M, N, LDA, INFO

REAL, DIMENSION(:) :: TAU, WORK


C INTERFACE
#include <sunperf.h>

void sgeqr2 (int m, int n, float *a, int lda, float *tau, int *info);


void sgeqr2_64 (long m, long n, float *a, long lda,  float  *tau,  long
*info);

Description

Oracle Solaris Studio Performance Library                           sgeqr2(3P)



NAME
       sgeqr2  - computes the QR factorization of a general rectangular matrix
       using an unblocked algorithm.


SYNOPSIS
       SUBROUTINE SGEQR2(M, N, A, LDA, TAU, WORK, INFO)


       INTEGER INFO, LDA, M, N

       REAL A(LDA,*), TAU(*), WORK(*)


       SUBROUTINE SGEQR2_64(M, N, A, LDA, TAU, WORK, INFO)


       INTEGER*8 INFO, LDA, M, N

       REAL A(LDA,*), TAU(*), WORK(*)


   F95 INTERFACE
       SUBROUTINE GEQR2(M, N, A, LDA, TAU, WORK, INFO)


       REAL, DIMENSION(:,:) :: A

       INTEGER :: M, N, LDA, INFO

       REAL, DIMENSION(:) :: TAU, WORK


       SUBROUTINE GEQR2_64(M, N, A, LDA, TAU, WORK, INFO)


       REAL, DIMENSION(:,:) :: A

       INTEGER(8) :: M, N, LDA, INFO

       REAL, DIMENSION(:) :: TAU, WORK


   C INTERFACE
       #include <sunperf.h>

       void sgeqr2 (int m, int n, float *a, int lda, float *tau, int *info);


       void sgeqr2_64 (long m, long n, float *a, long lda,  float  *tau,  long
                 *info);


PURPOSE
       sgeqr2 computes a QR factorization of a real m by n matrix A: A=Q*R.


ARGUMENTS
       M (input)
                 M is INTEGER
                 The number of rows of the matrix A.  M >= 0.


       N (input)
                 N is INTEGER
                 The number of columns of the matrix A.  N >= 0.


       A (input/output)
                 A is REAL array, dimension (LDA,N)
                 On entry, the m by n matrix A.
                 On  exit, the elements on and above the diagonal of the array
                 contain the min(m,n) by n upper trapezoidal matrix  R  (R  is
                 upper triangular if m >= n); the elements below the diagonal,
                 with the array TAU, represent the orthogonal matrix  Q  as  a
                 product of elementary reflectors (see Further Details).


       LDA (input)
                 LDA is INTEGER
                 The leading dimension of the array A.  LDA >= max(1,M).


       TAU (output)
                 TAU is REAL array, dimension (min(M,N))
                 The  scalar factors of the elementary reflectors (see Further
                 Details).


       WORK (output)
                 WORK is REAL array, dimension (N)


       INFO (output)
                 INFO is INTEGER
                 = 0: successful exit
                 < 0: if INFO = -i, the i-th argument had an illegal value


FURTHER DETAILS
       The matrix Q is represented as a product of elementary reflectors
           Q = H(1) H(2) . . . H(k), where k = min(m,n).
       Each H(i) has the form
           H(i) = I - tau * v * v**T
       where tau is a complex scalar, and v is a complex vector with  v(1:i-1)
       =  0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), and tau in
       TAU(i).



                                  7 Nov 2015                        sgeqr2(3P)