SRC/spttrs.f(3)

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💖 SRC/spttrs.f — Library Functions Manual 💖

okay bestie, welcome to SRC/spttrs.f(3) from the Library Functions Manual. 💅 This page is all about the spttrs subroutine, and it's giving solver energy. 🎀

✨ NAME ✨

SRC/spttrs.f — that's the file, and the function living in it is spttrs. No cap. 🦋

🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine spttrs (n, nrhs, d, e, b, ldb, info)
    SPTTRS

🦋 Function/Subroutine Documentation 🦋

subroutine spttrs

subroutine spttrs (integer n, integer nrhs, real, dimension( * ) d, real, dimension( * ) e, real, dimension( ldb, * ) b, integer ldb, integer info)
    SPTTRS

✨ Purpose ✨

ok so SPTTRS 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. Literally the whole pipeline. 🫶

🎀 Parameters 🎀

  • N — N is INTEGER. It's the order of the tridiagonal matrix A. Constraint: N >= 0. 💅
  • NRHS — NRHS is INTEGER. The number of right hand sides, i.e. the number of columns of the matrix B. Constraint: NRHS >= 0. 🌸
  • D — D is REAL array, dimension (N). These are 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). These are 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. Constraint: LDB >= max(1,N). 🎀
  • INFO — INFO is INTEGER. Status tea: = 0: successful exit; < 0: if INFO = -k, the k-th argument had an illegal value. 🫶

👑 Author 👑

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

Definition at line 108 of file spttrs.f. 📌

🌈 Author 🌈

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mwah 💋 that's the whole page, bestie — LAPACK, Version 3.12.0, for SRC/spttrs.f(3). Periodt. 💜

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