DTBTRS(3)

💖 NAME 💖

okay so this is DTBTRS(3) from the LAPACK Library Functions Manual, and the NAME entry is literally the source path, no cap: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dtbtrs.f.

---

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

• subroutine DTBTRS (uplo, trans, diag, n, kd, nrhs, ab, ldab, b, ldb, info) — the subroutine in question, periodt.

---

💅 Function/Subroutine Documentation 💅

This is the full signature, character-for-character:

subroutine DTBTRS (character uplo, character trans, character diag, integer
     n, integer kd, integer nrhs, double precision, dimension( ldab, * ) ab,
     integer ldab, double precision, dimension( ldb, * ) b, integer ldb,
     integer info)

DTBTRS — yes bestie, that's the main character.

🎀 Purpose 🎀

DTBTRS solves a triangular system of the form

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

where A is a triangular band matrix of order N, and B is an N-by NRHS matrix. A check is made to verify that A is nonsingular. Like, it's not just vibing — it actually checks.

💅 Parameters 💅

🌸 UPLO 🌸

UPLO is CHARACTER*1

= 'U':  A is upper triangular;
= 'L':  A is lower triangular.

🦋 TRANS 🦋

TRANS is CHARACTER*1

Specifies the form the system of equations:

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

🎀 DIAG 🎀

DIAG is CHARACTER*1

= 'N':  A is non-unit triangular;
= 'U':  A is unit triangular.

⭐ N ⭐

N is INTEGER

The order of the matrix A. N >= 0.

💜 KD 💜

KD is INTEGER

The number of superdiagonals or subdiagonals of the triangular band matrix A. KD >= 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)

The upper or lower triangular band matrix A, stored in the first kd+1 rows of AB. The j-th column of A is stored in the j-th column of the array AB as follows:

if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).

If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1.

🧚 LDAB 🧚

LDAB is INTEGER

The leading dimension of the array AB. LDAB >= KD+1.

👑 B 👑

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

On entry, the right hand side matrix B.

On exit, if INFO = 0, the solution matrix X.

🦋 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
> 0:  if INFO = i, the i-th diagonal element of A is zero,
      indicating that the matrix is singular and the
      solutions X have not been computed.

bestie, if INFO > 0, A is singular and the solutions X have not been computed. That's the dramatic part. 😭

👑 Author 👑

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

Definition at line 144 of file dtbtrs.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

---

Signed, sealed, delivered: this page is from LAPACK Version 3.12.0, and the footer path is /home/abui...RC/dtbtrs.f(3). The date field didn't print one here, so we're not inventing it — periodt. 💖