SRC/dgbtrs.f(3)

📦
version 3.12.1 · 4 versions
, in arch rolling

🎀 NAME 🎀

okay so this page is SRC/dgbtrs.f from the Library Functions Manual — it’s giving “LAPACK band-matrix solver who knows exactly what she’s doing,” and honestly? iconic. 💅

✨ SYNOPSIS ✨

Functions/Subroutines

subroutine dgbtrs (trans, n, kl, ku, nrhs, ab, ldab, ipiv, b, ldb, info)
           DGBTRS

🦋 Function/Subroutine Documentation 🦋

subroutine dgbtrs

subroutine dgbtrs (character trans, integer n, integer kl, integer ku,
       integer nrhs, double precision, dimension( ldab, * ) ab, integer ldab,
       integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b,
       integer ldb, integer info)

DGBTRS — main character energy, fr fr. 👑

💖 Purpose 💖

bestie, DGBTRS solves a system of linear equations:

A * X = B  or  A**T * X = B

with a general band matrix A using the LU factorization computed by DGBTRF. no cap, that’s the whole vibe. ✨

🌸 Parameters 🌸

TRANS

TRANS is CHARACTER*1. it specifies the form of the system of equations, and you must pick one:

  • = 'N': A * X = B (No transpose)
  • = 'T': A**T* X = B (Transpose)
  • = 'C': A**T* X = B (Conjugate transpose = Transpose)

N

N is INTEGER. the order of the matrix A. N >= 0. lowkey important. 💖

KL

KL is INTEGER. the number of subdiagonals within the band of A. KL >= 0.

KU

KU is INTEGER. the number of superdiagonals within the band of A. KU >= 0.

NRHS

NRHS is INTEGER. the number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.

AB

AB is DOUBLE PRECISION array, dimension (LDAB,N). details of the LU factorization of the band matrix A, as computed by DGBTRF.

U is stored as an upper triangular band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and the multipliers used during the factorization are stored in rows KL+KU+2 to 2*KL+KU+1. yes bestie, the rows are doing a whole choreography. 🩰

LDAB

LDAB is INTEGER. the leading dimension of the array AB. LDAB >= 2*KL+KU+1.

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). pivot girlies stay booked and busy. 💅

B

B is DOUBLE PRECISION array, dimension (LDB,NRHS).

On entry, the right hand side matrix B. on exit, the solution matrix X. glow-up complete. ✨

LDB

LDB is INTEGER. the leading dimension of the array B. LDB >= max(1,N).

INFO

INFO is INTEGER.

  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

👑 Author 👑

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

Definition at line 136 of file dgbtrs.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

byeee 💖 — this was LAPACK Version 3.12.0, page SRC/dgbtrs.f(3), signing off with immaculate band-matrix energy. 🫶✨

📦 where this page comes from