TESTING/MATGEN/slagsy.f(3)

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💅 TESTING/MATGEN/slagsy.f(3) 💅

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🌸 NAME 🌸

TESTING/MATGEN/slagsy.f — the manual page for this file, fr fr. 💖

✨ SYNOPSIS ✨

Functions/Subroutines

  • subroutine slagsy (n, k, d, a, lda, iseed, work, info) — SLAGSY

🦋 Function/Subroutine Documentation 🦋

💖 subroutine slagsy 💖

subroutine slagsy (integer n, integer k, real, dimension( * ) d, real,
     dimension( lda, * ) a, integer lda, integer, dimension( 4 ) iseed, real,
     dimension( * ) work, integer info)

⭐ SLAGSY ⭐

🎀 Purpose 🎀

Okay so SLAGSY 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. That's the tea. 🍓

💜 Parameters 💜

  • N — type check: N is INTEGER. N is the order of the matrix A. N >= 0.
  • K — type check: K is INTEGER. K is the number of nonzero subdiagonals within the band of A. 0 <= K <= N-1.
  • D — type check: D is REAL array, dimension (N). These are the diagonal elements of the diagonal matrix D.
  • A — type check: A is REAL array, dimension (LDA,N). This is the generated n by n symmetric matrix A (the full matrix is stored).
  • LDA — type check: LDA is INTEGER. This is the leading dimension of the array A. LDA >= N.
  • ISEED — type check: ISEED is INTEGER array, dimension (4). On entry, this is 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.
  • WORK — type check: WORK is REAL array, dimension (2*N).
  • INFO — type check: INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value.

💜 Author 💜

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

📍 Definition at line 100 of file slagsy.f.

👑 Author 👑

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