### ML_DGEQRF – Computes an QR factorization of a real M-by-N matrix A

Block SymbolLicensing group: MATRIX

Function Description

The output references yA, yTAU and yWORK are always set to the corresponding input references
uA, uTAU and uWORK. If HLD = on then nothing is computed otherwise the LAPACK function
DGEQRF is called internally:

DGEQRF(M, N, uA, LDA, uTAU, uWORK, LWORK, info);

where parameters of DGEQRF are set in the following way:

- M is number of rows of the matrix referenced by uA.
- N is number of columns of the matrix referenced by uA.
- LDA is the leading dimension of the matrix referenced by uA.
- LWORK is number of elements of the vector referenced by uWORK.
- info is return code from the function DGEQRF.

The error flag E is set to on if:

- the reference uA or uTAU or uWORK is not defined (i.e. input uA or uTAU or uWORK is not connected),
- number of elements of the vector referenced by uTAU is less than the minimum of number of rows and number of columns of the matrix referenced by uA.
- the call of the function DGEQRF returns error using the function XERBLA, see the return code info and system log.

See LAPACK documentation [7] for more details.

Inputs

uA | Input reference to matrix A | Reference |

uTAU | Input reference to vector of scalar factors of the elementary reflectors | Reference |

uWORK | Input reference to working vector WORK | Reference |

HLD | Hold | Bool |

Outputs

yA | Output reference to matrix A | Reference |

yTAU | Output reference to vector of scalar factors of the elementary reflectors | Reference |

yWORK | Output reference to working vector WORK | Reference |

E | Error indicator | Bool |

info | LAPACK function result info. If info = -i, the i=th argument had an illegal value | Long (I32) |

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