DGESC2(3)

DGESC2(3) 💅✨

okay so bestie, this is the Library Functions Manual page for DGESC2(3) — and it's lowkey a LAPACK icon because it's all about solving a system of linear equations with LU factorization and complete pivoting. Let's get into it fr fr. 🫶

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🌸 NAME 🌸

the file this page is literally about:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dgesc2.f

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✨ SYNOPSIS ✨

Functions/Subroutines

• subroutine DGESC2 (n, a, lda, rhs, ipiv, jpiv, scale) — DGESC2 solves a system of linear equations using the LU factorization with complete pivoting computed by sgetc2. (yes bestie, the synopsis says sgetc2 with a lowercase s, and the Purpose block says DGETC2 — both are literally in the original, I'm not fixing it 💀)

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💖 Function/Subroutine Documentation 💖

here's the full signature, exactly as the page gives it:

   subroutine DGESC2 (integer n, double precision, dimension( lda, * ) a,
       integer lda, double precision, dimension( * ) rhs, integer, dimension( *
       ) ipiv, integer, dimension( * ) jpiv, double precision scale)

DGESC2 solves a system of linear equations using the LU factorization with complete pivoting computed by sgetc2.

🎀 Purpose 🎀

the source literally says this:

!>
!> DGESC2 solves a system of linear equations
!>
!>           A * X = scale* RHS
!>
!> with a general N-by-N matrix A using the LU factorization with
!> complete pivoting computed by DGETC2.
!>

translation, bestie: it solves A * X = scale* RHS for a general N-by-N matrix A, using the LU factorization with complete pivoting computed by DGETC2. iconic behavior. 👑

🦋 Parameters 🦋

• N — N is INTEGER. it's the order of the matrix A. periodt.
• A — A is DOUBLE PRECISION array, dimension (LDA,N). On entry, it's the LU part of the factorization of the n-by-n matrix A computed by DGETC2: A = P * L * U * Q. so yes, it comes pre-factored, don't just throw any old matrix in there.
• LDA — LDA is INTEGER. it's the leading dimension of the array A, and LDA >= max(1, N). respect the leading dimension, bestie.
• RHS — RHS is DOUBLE PRECISION array, dimension (N). On entry, it's the right hand side vector b. On exit, it's the solution vector X. glow-up moment for real. ✨
• IPIV — IPIV is INTEGER array, dimension (N). these are the pivot indices; for 1 <= i <= N, row i of the matrix has been interchanged with row IPIV(i). row swaps, no cap.
• JPIV — JPIV is INTEGER array, dimension (N). these are the pivot indices; for 1 <= j <= N, column j of the matrix has been interchanged with column JPIV(j). column swaps too, complete pivoting said slay. 💅
• SCALE — SCALE is DOUBLE PRECISION. On exit, SCALE contains the scale factor. SCALE is chosen 0 <= SCALE <= 1 to prevent overflow in the solution. tiny scale factor, big anti-overflow energy. 🫶

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👑 Author 👑

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

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🎀 Contributors 🎀

Bo Kagstrom and Peter Poromaa, Department of Computing Science, Umea University, S-901 87 Umea, Sweden.

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🦋 Definition at line 🦋

Definition at line 113 of file dgesc2.f.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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okay bestie that's the whole page!! sign-off: LAPACK Version 3.12.0 — path is /home/abui...RC/dgesc2.f(3) 💅✨