SRC/sgtts2.f(3)

💖 NAME 💖

SRC/sgtts2.f — bestie, that's the page name, and welcome to the Library Functions Manual corner of the universe. This is the sgtts2 subroutine page and it is lowkey iconic. ✨

🌸 SYNOPSIS 🌸

Functions/Subroutines

• subroutine sgtts2 (itrans, n, nrhs, dl, d, du, du2, ipiv, b, ldb) — SGTTS2 solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf.

🫶 Function/Subroutine Documentation 🫶

Here's the full signature, no cap:

subroutine sgtts2 (integer itrans, integer n, integer nrhs, real, dimension(
* ) dl, real, dimension( * ) d, real, dimension( * ) du, real,
dimension( * ) du2, integer, dimension( * ) ipiv, real, dimension( ldb,
* ) b, integer ldb)

SGTTS2 solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf.

🎀 Purpose 🎀

Okay so the whole assignment is literally this: SGTTS2 solves one of the systems of equations

• A*X = B
• A**T*X = B

with a tridiagonal matrix A using the LU factorization computed by SGTTRF. That's it, that's the vibe, and it ate. 💅

🦋 Parameters 🦋

• ITRANS — ITRANS is INTEGER. It specifies the form of the system of equations:
  • = 0: A * X = B (No transpose)
  • = 1: A**T* X = B (Transpose)
  • = 2: A**T* X = B (Conjugate transpose = Transpose)
• N — N is INTEGER. The order of the matrix A.
• NRHS — NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
• DL — DL is REAL array, dimension (N-1). The (n-1) multipliers that define the matrix L from the LU factorization of A.
• D — D is REAL array, dimension (N). The n diagonal elements of the upper triangular matrix U from the LU factorization of A.
• DU — DU is REAL array, dimension (N-1). The (n-1) elements of the first super-diagonal of U.
• DU2 — DU2 is REAL array, dimension (N-2). 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.
• B — B is REAL array, dimension (LDB,NRHS). On entry, the matrix of right hand side vectors B. On exit, B is overwritten by the solution vectors X.
• LDB — LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N).

👑 Author 👑

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

Definition at line 127 of file sgtts2.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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That's the whole page, bestie — signed off from the LAPACK corner, Version 3.12.0, source SRC/sgtts2.f(3). 🦋💖