/home/abui.../spotrf2.f(3)

💖 NAME 💖

okay bestie, welcome to the Library Functions Manual page for this file — yes, the whole path is the NAME, no cap:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/spotrf2.f

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines

recursive subroutine SPOTRF2 (uplo, n, a, lda, info)

SPOTRF2 — the main character 💅

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💅 Function/Subroutine Documentation 💅

recursive subroutine SPOTRF2 (character uplo, integer n, real, dimension(
       lda, * ) a, integer lda, integer info)

SPOTRF2

🌸 Purpose

okay so SPOTRF2 computes the Cholesky factorization of a real symmetric positive definite matrix A using the recursive algorithm. periodt.

The factorization has the form:

A = U**T * U,  if UPLO = 'U', or
A = L  * L**T,  if UPLO = 'L',

where U is an upper triangular matrix and L is lower triangular.

This is the recursive version of the algorithm. It divides the matrix into four submatrices:

        [  A11 | A12  ]  where A11 is n1 by n1 and A22 is n2 by n2
    A = [ -----|----- ]  with n1 = n/2
        [  A21 | A22  ]       n2 = n-n1

The subroutine calls itself to factor A11. Update and scale A21 or A12, update A22 then call itself to factor A22. literally recursive main character energy 🔁✨

🎀 Parameters

• UPLO — CHARACTER*1. = 'U': upper triangle of A is stored; = 'L': lower triangle of A is stored.
• N — INTEGER. The order of the matrix A. N >= 0.
• A — REAL array, dimension (LDA,N). On entry, the symmetric matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit, if INFO = 0, the factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• INFO — INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. > 0: if INFO = i, the leading principal minor of order i is not positive, and the factorization could not be completed.

bestie, if INFO > 0, the factorization could not be completed — the leading principal minor of order i is not positive. that's the warning vibe 🫶

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👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 105 of file spotrf2.f.

🪄 Author 🪄

Generated automatically by Doxygen for LAPACK from the source code.

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okay that’s the whole page, bestie 💖 this iconic source/version is LAPACK Version 3.12.0, and the source page is /home/abui.../spotrf2.f(3). byeee 💅✨