sgetrf.f(3)

💖 NAME 💖

Okay so bestie, welcome to the sgetrf.f(3) page — that's the manual name and it's from LAPACK, periodt. This is the page for sgetrf.f, and the whole vibe is the left-looking Level 3 BLAS version of the LU factorization algorithm. Iykyk. 💅

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine sgetrf (M, N, A, LDA, IPIV, INFO)

SGETRF VARIANT: left-looking Level 3 BLAS version of the algorithm.

No cap, that's the whole synopsis — short and iconic. 🎀

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🌸 Function/Subroutine Documentation 🌸

💅 subroutine sgetrf

subroutine sgetrf (integer M, integer N, real, dimension( lda, * ) A,
    integer LDA, integer, dimension( * ) IPIV, integer INFO)

SGETRF VARIANT: left-looking Level 3 BLAS version of the algorithm.

🎀 Purpose:

SGETRF 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. Slay. ✨

🌈 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 REAL 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.

Lowkey important: when INFO > 0, the factorization finished but U is exactly singular — so if you use it to solve systems, division by zero is coming. Not a cute look. 😭

👑 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/sgetrf.f.

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💜 Author 💜

Generated automatically by Doxygen for LAPACK from the source code.

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That's the whole vibe check, bestie — this page is from LAPACK Version 3.8.0, dated Tue Nov 14 2017, and it's literally the sgetrf.f(3) page. Bye 💅✨🫶