SRC/slarrc.f(3)

SRC/slarrc.f(3) — from the Library Functions Manual ✨ okay bestie, let's get into it.

🌸 NAME 🌸

SRC/slarrc.f — that's the whole name section, and honestly it's giving main character subroutine energy.

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine slarrc (jobt, n, vl, vu, d, e, pivmin, eigcnt, lcnt, rcnt,
    info)

SLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix. No cap.

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🦋 Function/Subroutine Documentation 🦋

subroutine slarrc (character jobt, integer n, real vl, real vu, real,
    dimension( * ) d, real, dimension( * ) e, real pivmin, integer eigcnt,
    integer lcnt, integer rcnt, integer info)

SLARRC computes the number of eigenvalues of the symmetric tridiagonal matrix. Iconic behavior, truly.

💖 Purpose 💖

Find the number of eigenvalues of the symmetric tridiagonal matrix T that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T if JOBT = 'L'.

🎀 Parameters 🎀

• JOBT — CHARACTER*1. = 'T': Compute Sturm count for matrix T. = 'L': Compute Sturm count for matrix L D L^T.
• N — INTEGER. The order of the matrix. N > 0.
• VL — REAL. The lower bound for the eigenvalues.
• VU — REAL. The upper bound for the eigenvalues.
• D — REAL array, dimension (N). JOBT = 'T': The N diagonal elements of the tridiagonal matrix T. JOBT = 'L': The N diagonal elements of the diagonal matrix D.
• E — REAL array, dimension (N). JOBT = 'T': The N-1 offdiagonal elements of the matrix T. JOBT = 'L': The N-1 offdiagonal elements of the matrix L.
• PIVMIN — REAL. The minimum pivot in the Sturm sequence for T.
• EIGCNT — INTEGER. The number of eigenvalues of the symmetric tridiagonal matrix T that are in the interval (VL,VU].
• LCNT — INTEGER. That's the whole note for this one on the page, bestie.
• RCNT — INTEGER. The left and right negcounts of the interval.
• INFO — INTEGER. Also no extra description here — it just says INTEGER.

👑 Author 👑

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

🌈 Contributors: 🌈

• Beresford Parlett, University of California, Berkeley, USA
• Jim Demmel, University of California, Berkeley, USA
• Inderjit Dhillon, University of Texas, Austin, USA
• Osni Marques, LBNL/NERSC, USA
• Christof Voemel, University of California, Berkeley, USA

Definition at line 135 of file slarrc.f.

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💫 Author 💫

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