DLANGT(3)

💅 dlangt.f(3) — LAPACK Library Functions Manual 🦋

okay so this is the manual page for dlangt.f(3) from LAPACK, and bestie, it's literally about measuring how big a tridiagonal matrix is. iykyk. let's get into it ✨

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🌸 NAME

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dlangt.f

(that's the whole file path as its own name, don't ask, that's just how the manpage came out of the build, we love that for it 🎀)

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✨ 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. iconic behaviour honestly 👑

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💖 Function/Subroutine Documentation

⭐ double precision function DLANGT (character norm, integer n, double precision, dimension( * ) dl, double precision, dimension( * ) d, double precision, dimension( * ) 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. no cap, that's the whole gig 💅

🔥 Purpose:

!>
!> 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.
!>

🌈 Returns

DLANGT

!>
!>    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.
!>

⚠️ bestie read that last bit again: max(abs(A(i,j))) is not a consistent matrix norm. it's just vibes, not a real norm. the manpage said what it said 💀

🎀 Parameters

• NORM — NORM is CHARACTER*1. Specifies the value to be returned in DLANGT as described above. you're picking the flavour here 🍓

!>          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. zero is a valid answer, we love a clean edge case ✨

!>          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. the below-the-line squad 🫶

!>          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. main character energy, literally the centre of attention 👑

!>          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. the above-the-line squad 🦋

!>          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. 📍

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💜 Author

Generated automatically by Doxygen for LAPACK from the source code.

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okay that's the whole page, and fr fr it's shorter than it looks 😭 sign-off time: this was LAPACK, Version 3.12.0, served fresh from /home/abui...RC/dlangt.f(3) — ty for coming to my ted talk, mwah 🎀💖🧚