SRC/cgtts2.f(3)

💅 SRC/cgtts2.f — Library Functions Manual 🎀

okay bestie, welcome to the manual page for SRC/cgtts2.f from the Library Functions Manual. yes it's a Fortran file, yes it's iconic, let's get into it ✨

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🌸 NAME 🌸

SRC/cgtts2.f — literally the whole name section, no cap 🫶

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine cgtts2 (itrans, n, nrhs, dl, d, du, du2, ipiv, b, ldb)

CGTTS2 solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf. (yes, sgttrf, that's what it says, don't come for me 💀)

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🦋 Function/Subroutine Documentation 🦋

subroutine cgtts2 (integer itrans, integer n, integer nrhs, complex,
    dimension( * ) dl, complex, dimension( * ) d, complex, dimension( * )
    du, complex, dimension( * ) du2, integer, dimension( * ) ipiv, complex,
    dimension( ldb, * ) b, integer ldb)

CGTTS2 solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf. (still sgttrf. still keeping it 💅)

🔥 Purpose 🔥

CGTTS2 solves one of the systems of equations

A * X = B,  A**T * X = B,  or  A**H * X = B,

with a tridiagonal matrix A using the LU factorization computed by CGTTRF. (and here it says CGTTRF. both are in the original, so both are staying, periodt 🫡)

🎀 Parameters 🎀

• ITRANS — INTEGER. Specifies the form of the system of equations:
  • = 0: A * X = B (No transpose)
  • = 1: A**T * X = B (Transpose)
  • = 2: A**H * X = B (Conjugate transpose)
• N — INTEGER. The order of the matrix A. 💫
• NRHS — INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
• DL — COMPLEX array, dimension (N-1). The (n-1) multipliers that define the matrix L from the LU factorization of A.
• D — COMPLEX array, dimension (N). The n diagonal elements of the upper triangular matrix U from the LU factorization of A. so iconic of them 🧚
• DU — COMPLEX array, dimension (N-1). The (n-1) elements of the first super-diagonal of U.
• DU2 — COMPLEX array, dimension (N-2). The (n-2) elements of the second super-diagonal of U.
• IPIV — 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. (so well-behaved 😌)
• B — COMPLEX array, dimension (LDB,NRHS). On entry, the matrix of right hand side vectors B. On exit, B is overwritten by the solution vectors X. ⚠️ heads up: your input B does not survive this, it gets replaced fr fr.
• LDB — INTEGER. The leading dimension of the array B. LDB >= max(1,N).

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👑 Author 👑

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

Definition at line 127 of file cgtts2.f. 📍

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🌈 Author (the Doxygen one) 🌈

Generated automatically by Doxygen for LAPACK from the source code. 🤖

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no bugs listed, no warnings beyond the ones baked into the params — so you're chilling, just respect that LDB >= max(1,N) and that B gets clobbered 🩷

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okay that's the whole page, bestie — you ate that 🍓 this lil recap was brought to you by LAPACK, Version 3.12.0, covering SRC/cgtts2.f(3). mwah 💖✨🎀