SRC/sptts2.f(3)

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💖 SRC/sptts2.f(3) — Library Functions Manual energy 💖

okay bestie, welcome to SRC/sptts2.f(3) from the Library Functions Manual. This is the page for a LAPACK subroutine that is lowkey doing very important tridiagonal solve business, and we are going to read it together like the group chat is watching. 💅

✨ NAME ✨

SRC/sptts2.f

🦋 SYNOPSIS 🦋

💫 Functions/Subroutines 💫

  • subroutine sptts2 (n, nrhs, d, e, b, ldb) — SPTTS2 solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

🎀 Function/Subroutine Documentation 🎀

🌸 subroutine sptts2 🌸

subroutine sptts2 (integer n, integer nrhs, real, dimension( * ) d, real,
       dimension( * ) e, real, dimension( ldb, * ) b, integer ldb)

SPTTS2 solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf. No cap, that is the whole serve. 🫶

🌟 Purpose 🌟

Okay so SPTTS2 solves a tridiagonal system of the form

A * X = B

using the L*D*L**T factorization of A computed by SPTTRF. D is a diagonal matrix specified in the vector D, L is a unit bidiagonal matrix whose subdiagonal is specified in the vector E, and X and B are N by NRHS matrices. It's giving "factorization already happened, now we solve" energy. ✨

🌈 Parameters 🌈

  • 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 L*D*L**T factorization of A.
  • E — E is REAL array, dimension (N-1). The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**T factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U**T*D*U.
  • B — B is REAL 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 101 of file sptts2.f.

👑 Author 👑

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and that's the page, bestie: LAPACK Version 3.12.0 energy for SRC/sptts2.f(3), signed off with all the sparkle it deserves. mwah 💋🎀

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