GELQT3 - 5.2 English - 68552

AOCL API Guide (68552)

Document ID
68552
Release Date
2025-12-29
Version
5.2 English
template<typename T>
void gelqt3(integer *m, integer *n, T *a, integer *lda, T *t, integer *ldt, integer *info)#

GELQT3 recursively computes a LQ factorization of a real M-by-N matrix A.

Purpose:

 GELQT3 recursively computes a LQ factorization of a real M-by-N
 matrix A, using the compact WY representation of Q.

 Based on the algorithm of Elmroth and Gustavson,
 IBM J. Res. Develop. Vol 44 No. 4 July 2000.
Parameters:
  • M[in]

    M is INTEGER

    The number of rows of the matrix A. M =< N.

  • N[in]

    N is INTEGER

    The number of columns of the matrix A. N >= 0.

  • A[inout]

    A is REAL array, dimension (LDA,N)

    On entry, the real M-by-N matrix A. On exit, the elements on and below the diagonal contain the N-by-N lower triangular matrix L; the elements above the diagonal are the rows of V. See below for further details.

  • LDA[in]

    LDA is INTEGER

    The leading dimension of the array A. LDA >= fla_max(1,M).

  • T[out]

    T is REAL array, dimension (LDT,N)

    The N-by-N upper triangular factor of the block reflector. The elements on and above the diagonal contain the block reflector T; the elements below the diagonal are not used. See below for further details.

  • LDT[in]

    LDT is INTEGER

    The leading dimension of the array T. LDT >= fla_max(1,N).

  • INFO[out]

    INFO is INTEGER

    = 0: successful exit

    < 0: if INFO = -i, the i-th argument had an illegal value