sterf(3)

📦
version 3.12.1 · 9 versions
, in arch rolling

🎀 NAME 🎀

okay so bestie, this is sterf(3) from the Library Functions Manual — yes, the manual name is literally folded right in here with love. 💖

  • sterf — sterf: eig, QR iteration

✨ SYNOPSIS ✨

🎀 Functions 🎀

Here’s the function roster — two subroutines, same iconic energy:

subroutine dsterf (n, d, e, info)
    DSTERF
subroutine ssterf (n, d, e, info)
    SSTERF

💫 Detailed Description 💫

There’s no extra prose in this section in the source — it goes straight into the function docs. Buckle up, we’re going in. 🦋

🔥 Function Documentation 🔥

💖 subroutine dsterf 💖

subroutine dsterf (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, integer info)

DSTERF

🦋 Purpose 🦋

DSTERF computes all eigenvalues of a symmetric tridiagonal matrix using the Pal-Walker-Kahan variant of the QL or QR algorithm. That’s the whole glow-up. ✨

🌸 Parameters 🌸

  • N — N is INTEGER. The order of the matrix. N >= 0.
  • D — D is DOUBLE PRECISION array, dimension (N). On entry, the n diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order.
  • E — E is DOUBLE PRECISION array, dimension (N-1). On entry, the (n-1) subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed.
  • INFO — INFO is INTEGER.
    • = 0: successful exit
    • < 0: if INFO = -i, the i-th argument had an illegal value
    • > 0: the algorithm failed to find all of the eigenvalues in a total of 30*N iterations; if INFO = i, then i elements of E have not converged to zero.

👑 Author 👑

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

Definition at line 85 of file dsterf.f.

💖 subroutine ssterf 💖

subroutine ssterf (integer n, real, dimension( * ) d, real, dimension( * ) e, integer info)

SSTERF

🦋 Purpose 🦋

SSTERF computes all eigenvalues of a symmetric tridiagonal matrix using the Pal-Walker-Kahan variant of the QL or QR algorithm. Same slay, single-precision edition. 💅

🌸 Parameters 🌸

  • N — N is INTEGER. The order of the matrix. N >= 0.
  • D — D is REAL array, dimension (N). On entry, the n diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order.
  • E — E is REAL array, dimension (N-1). On entry, the (n-1) subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed.
  • INFO — INFO is INTEGER.
    • = 0: successful exit
    • < 0: if INFO = -i, the i-th argument had an illegal value
    • > 0: the algorithm failed to find all of the eigenvalues in a total of 30*N iterations; if INFO = i, then i elements of E have not converged to zero.

👑 Author 👑

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

Definition at line 85 of file ssterf.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

Cute sign-off: the source is LAPACK, version 3.12.0 🌟 — and the original footer’s date slot has no separate date shown, just the sterf(3) tag on the right. 🫶💅

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