/home/abui...N/dlagsy.f(3)

🦋 NAME 🦋

okay so picture this: /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/MATGEN/dlagsy.f — that's the file, bestie. it's giving "LAPACK testing matrix generator" main character energy, and it lives in the Library Functions Manual, section 3. literally the blueprint for DLAGSY, no cap 💅

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✨ SYNOPSIS ✨

🌸 Functions/Subroutines

• subroutine DLAGSY (n, k, d, a, lda, iseed, work, info) — DLAGSY 🫶 (yes that's the whole description, she's mysterious like that)

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👑 Function/Subroutine Documentation 👑

subroutine DLAGSY (integer n, integer k, double precision, dimension( * ) d,
    double precision, dimension( lda, * ) a, integer lda, integer,
    dimension( 4 ) iseed, double precision, dimension( * ) work, integer
    info)

DLAGSY ⭐

💖 Purpose:

!>
!> DLAGSY generates a real symmetric matrix A, by pre- and post-
!> multiplying a real diagonal matrix D with a random orthogonal matrix:
!> A = U*D*U'. The semi-bandwidth may then be reduced to k by additional
!> orthogonal transformations.
!>

so basically: take your diagonal D, sandwich it with a random orthogonal U on both sides (A = U*D*U'), and boom — real symmetric matrix, freshly generated ✨. and if you're not satisfied with the semi-bandwidth, you can shrink it down to k with some extra orthogonal transformations. highkey iconic behavior 🧚

🌈 Parameters

• N

!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>

• K

!>          K is INTEGER
!>          The number of nonzero subdiagonals within the band of A.
!>          0 <= K <= N-1.
!>

• D

!>          D is DOUBLE PRECISION array, dimension (N)
!>          The diagonal elements of the diagonal matrix D.
!>

• A

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          The generated n by n symmetric matrix A (the full matrix is
!>          stored).
!>

• LDA

!>          LDA is INTEGER
!>          The leading dimension of the array A.  LDA >= N.
!>

• ISEED

!>          ISEED is INTEGER array, dimension (4)
!>          On entry, the seed of the random number generator; the array
!>          elements must be between 0 and 4095, and ISEED(4) must be
!>          odd.
!>          On exit, the seed is updated.
!>

🫶 heads up bestie: those ISEED elements gotta be between 0 and 4095, and ISEED(4) must be odd. and she mutates it — on exit the seed is updated, so don't be surprised when it's not what you handed her 🙈

• WORK

!>          WORK is DOUBLE PRECISION array, dimension (2*N)
!>

• INFO

!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -i, the i-th argument had an illegal value
!>

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🎀 Author 🎀

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

Definition at line 100 of file dlagsy.f. 📍

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⭐ Author ⭐

Generated automatically by Doxygen for LAPACK from the source code. (not me writing this by hand, the robots did it 🤖✨)

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okay and that's the whole page, periodt 💅 last little thing — the footer says LAPACK Version 3.12.0, dated /home/abui...N/dlagsy.f(3). mwah, go generate some symmetric matrices bestie 🍓🦋