# VARIANTS_lu_LL_cgetrf.f - Man Page

cgetrf.f

## Synopsis

### Functions/Subroutines

subroutine **cgetrf** (M, **N**, A, **LDA**, IPIV, INFO)**CGETRF** VARIANT: left-looking Level 3 BLAS version of the algorithm.

## Function/Subroutine Documentation

### subroutine cgetrf (integer M, integer N, complex, dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV, integer INFO)

**CGETRF** VARIANT: left-looking Level 3 BLAS version of the algorithm. **Purpose:**

CGETRF computes an LU factorization of a general M-by-N matrix A using partial pivoting with row interchanges. The factorization has the form A = P * L * U where P is a permutation matrix, L is lower triangular with unit diagonal elements (lower trapezoidal if m > n), and U is upper triangular (upper trapezoidal if m < n). This is the left-looking Level 3 BLAS version of the algorithm.

**Parameters:***M*M is INTEGER The number of rows of the matrix A. M >= 0.

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

*A*A is COMPLEX array, dimension (LDA,N) On entry, the M-by-N matrix to be factored. On exit, the factors L and U from the factorization A = P*L*U; the unit diagonal elements of L are not stored.

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

*IPIV*IPIV is INTEGER array, dimension (min(M,N)) The pivot indices; for 1 <= i <= min(M,N), row i of the matrix was interchanged with row IPIV(i).

*INFO*INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, and division by zero will occur if it is used to solve a system of equations.

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 102 of file VARIANTS/lu/LL/cgetrf.f.

## Author

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## Info

Tue Nov 14 2017 Version 3.8.0 LAPACK