CTBTRS(3)

💖 CTBTRS(3) — Library Functions Manual 💖

okay so bestie, welcome to the Library Functions Manual page for CTBTRS. This is the whole vibe, and yes, we're keeping every flag, every parameter, every "do not mess with this" detail. 💅

🌸 NAME 🌸

This page is for /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/ctbtrs.f — the whole path, no cap. It's the Fortran source file behind CTBTRS, and this is its manual-page era. 🎀

✨ SYNOPSIS ✨

🌈 Functions/Subroutines 🌈

       subroutine CTBTRS (uplo, trans, diag, n, kd, nrhs, ab, ldab, b, ldb,
           info)
           CTBTRS

📚 Function/Subroutine Documentation 📚

Here's the full signature, verbatim, because signatures are not a vibe we improvise:

   subroutine CTBTRS (character uplo, character trans, character diag, integer
       n, integer kd, integer nrhs, complex, dimension( ldab, * ) ab, integer
       ldab, complex, dimension( ldb, * ) b, integer ldb, integer info)
       CTBTRS

🎯 Purpose 🎯

okay so CTBTRS solves a triangular system of the form

A * X = B,  A**T * X = B,  or  A**H * 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. Yes, bestie, it's doing a whole vibe check on singularity. ✨

🧾 Parameters 🧾

• UPLO — UPLO is CHARACTER*1. This is the "which triangle are we in" selector:
  • = 'U': A is upper triangular;
  • = 'L': A is lower triangular.

Pick one, and keep it moving. 💫

• TRANS — TRANS is CHARACTER*1. Specifies the form of the system of equations:
  • = 'N': A * X = B (No transpose)
  • = 'T': A**T * X = B (Transpose)
  • = 'C': A**H * X = B (Conjugate transpose)

That's the menu, and there are exactly three choices. No secret fourth option. 😌

• DIAG — DIAG is CHARACTER*1. Is A being its non-unit self or a unit-triangular icon?
  • = 'N': A is non-unit triangular;
  • = 'U': A is unit triangular.
• N — N is INTEGER. The order of the matrix A. N >= 0. No negative-order nonsense, periodt.
• 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 COMPLEX 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. Lowkey important, highkey iconic. 🫶

• LDAB — LDAB is INTEGER. The leading dimension of the array AB. LDAB >= KD+1.
• B — B is COMPLEX 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. This is the exit-status bestie:

= 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.

So if INFO > 0, that's the "matrix is singular, X did not get computed" warning. Do not ignore it, fr fr. 🚨

👑 Author 👑

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

Definition at line 144 of file ctbtrs.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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💖 okay that's the whole manual, no cap. Footer cutie check: LAPACK Version 3.12.0 + source path /home/abui...RC/ctbtrs.f(3) — mwah, bye bestie! 💖