SRC/dlangt.f(3)

📦
version 3.12.1 · 7 versions
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💅 NAME 💅

okay so this is SRC/dlangt.f, from the Library Functions Manual (section 3), and it’s lowkey all about the Fortran function dlangt. ngl, it’s giving math-girl main character energy. 🫶

✨ SYNOPSIS ✨

🎀 Functions/Subroutines 🎀

  • double precision function dlangt (norm, n, dl, d, du) — DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix.

🦋 Function/Subroutine Documentation 🦋

Here’s the full signature, bestie:

double precision function dlangt (character norm, integer n, double precision, dimension( * ) dl, double precision, dimension( * ) d, double precision, dimension( * ) du)

The vibe check: DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general tridiagonal matrix. iconic.

🌸 Purpose 🌸

Bestie, DLANGT returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real tridiagonal matrix A. That’s the whole assignment, no cap. 💅

💖 Returns 💖

The return value is DLANGT, and the exact mapping is:

!>
!>    DLANGT = ( max(abs(A(i,j))), NORM = 'M' or 'm'
!>             (
!>             ( norm1(A),         NORM = '1', 'O' or 'o'
!>             (
!>             ( normI(A),         NORM = 'I' or 'i'
!>             (
!>             ( normF(A),         NORM = 'F', 'f', 'E' or 'e'
!>
!> where  norm1  denotes the  one norm of a matrix (maximum column sum),
!> normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
!> normF  denotes the  Frobenius norm of a matrix (square root of sum of
!> squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.
!>

🎀 Parameters 🎀

  • NORM — NORM is CHARACTER*1. Specifies the value to be returned in DLANGT as described above. ✨
  • N — N is INTEGER. The order of the matrix A. N >= 0. When N = 0, DLANGT is set to zero. 🫶
  • DL — DL is DOUBLE PRECISION array, dimension (N-1). The (n-1) sub-diagonal elements of A. 💜
  • D — D is DOUBLE PRECISION array, dimension (N). The diagonal elements of A. 🌸
  • DU — DU is DOUBLE PRECISION array, dimension (N-1). The (n-1) super-diagonal elements of A. 🦋

👑 Author 👑

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

Definition at line 105 of file dlangt.f.

💫 Author 💫

Generated automatically by Doxygen for LAPACK from the source code.

okay that’s the whole page, bestie. It’s from the LAPACK manual, Version 3.12.0, and the source page is SRC/dlangt.f(3). slay. 💖✨🫶

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