SRC/cptts2.f(3)

💖 NAME 💖

SRC/cptts2.f — that's the name, bestie. This page lives in the Library Functions Manual, and we're about to make a tridiagonal solve feel like a group-chat win. 🎀

✨ SYNOPSIS ✨

🫶 Functions/Subroutines

• subroutine cptts2 (iuplo, n, nrhs, d, e, b, ldb) — CPTTS2 solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

🦋 Function/Subroutine Documentation 🦋

💅 subroutine cptts2

subroutine cptts2 (integer iuplo, integer n, integer nrhs, real, dimension(
       * ) d, complex, dimension( * ) e, complex, dimension( ldb, * ) b,
       integer ldb)

CPTTS2 solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

🌸 Purpose

okay so CPTTS2 solves a tridiagonal system of the form

A * X = B

using the factorization A = U**H*D*U or A = L*D*L**H computed by CPTTRF. D is a diagonal matrix specified in the vector D, U (or L) is a unit bidiagonal matrix whose superdiagonal (subdiagonal) is specified in the vector E, and X and B are N by NRHS matrices. ✨

🎀 Parameters

• IUPLO — IUPLO is INTEGER. Specifies the form of the factorization and whether the vector E is the superdiagonal of the upper bidiagonal factor U or the subdiagonal of the lower bidiagonal factor L. = 1: A = U**H *D*U, E is the superdiagonal of U; = 0: A = L*D*L**H, E is the subdiagonal of L. 💅
• N — N is INTEGER. The order of the tridiagonal matrix A. N >= 0.
• NRHS — NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
• D — D is REAL array, dimension (N). The n diagonal elements of the diagonal matrix D from the factorization A = U**H *D*U or A = L*D*L**H.
• E — E is COMPLEX array, dimension (N-1). If IUPLO = 1, the (n-1) superdiagonal elements of the unit bidiagonal factor U from the factorization A = U**H*D*U. If IUPLO = 0, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the factorization A = L*D*L**H. 🦋
• B — B is COMPLEX array, dimension (LDB,NRHS). On entry, the right hand side vectors B for the system of linear equations. On exit, 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 112 of file cptts2.f.

🌈 Author 🌈

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