SGTTRF(3)

hey bestie 💖 welcome to SGTTRF(3) from the Library Functions Manual. This page is literally about /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/sgttrf.f, and it’s giving real tridiagonal matrix LU factorization main-character energy. 🦋

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NAME 🌸

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

SYNOPSIS ✨

Functions/Subroutines:

       subroutine SGTTRF (n, dl, d, du, du2, ipiv, info)
           SGTTRF

Function/Subroutine Documentation 💖

   subroutine SGTTRF (integer n, real, dimension( * ) dl, real, dimension( * )
       d, real, dimension( * ) du, real, dimension( * ) du2, integer,
       dimension( * ) ipiv, integer info)

SGTTRF

Purpose 🎀

okay so SGTTRF computes an LU factorization of a real tridiagonal matrix A using elimination with partial pivoting and row interchanges. no cap.

The factorization has the form:

A = L * U

where L is a product of permutation and unit lower bidiagonal matrices and U is upper triangular with nonzeros in only the main diagonal and first two superdiagonals. periodt. 💅

Parameters 🦋

• N — N is INTEGER. It’s the order of the matrix A. 👑
• DL — DL is REAL array, dimension (N-1). On entry, DL must contain the (n-1) sub-diagonal elements of A.

On exit, DL is overwritten by the (n-1) multipliers that define the matrix L from the LU factorization of A. 🫶

• D — D is REAL array, dimension (N). On entry, D must contain the diagonal elements of A.

On exit, D is overwritten by the n diagonal elements of the upper triangular matrix U from the LU factorization of A. 💜

• DU — DU is REAL array, dimension (N-1). On entry, DU must contain the (n-1) super-diagonal elements of A.

On exit, DU is overwritten by the (n-1) elements of the first super-diagonal of U. ⭐

• DU2 — DU2 is REAL array, dimension (N-2). On exit, DU2 is overwritten by the (n-2) elements of the second super-diagonal of U. 🦋
• IPIV — IPIV is INTEGER array, dimension (N). The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required. 🔥
• INFO — INFO is INTEGER
  • = 0: successful exit
  • < 0: if INFO = -k, the k-th argument had an illegal value
  • > 0: if INFO = k, U(k,k) 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.

Definition at line 123 of file sgttrf.f. 📍

Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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xoxo bestie 🫶 — the footer tea is LAPACK Version 3.12.0 and /home/abui...RC/sgttrf.f(3). No separate date line, just those, periodt. 💖