SSYL01(3)

📦 version 3.12.0, in opensuse-leap 16.0

💖 SSYL01(3) — Library Functions Manual 💖

okay so bestie, this is the SSYL01(3) page from the Library Functions Manual — yes, the manual name is right there in the header vibe. The header/footer tag uses the cute truncated path /home/abui...IG/ssyl01.f(3), and this page is about a Fortran test routine. Slay.

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/EIG/ssyl01.f

✨ SYNOPSIS ✨

Functions/Subroutines

  • subroutine SSYL01 (thresh, nfail, rmax, ninfo, knt) — SSYL01

🦋 Function/Subroutine Documentation 🦋

subroutine SSYL01 (real thresh, integer, dimension( 3 ) nfail, real,
       dimension( 2 ) rmax, integer, dimension( 2 ) ninfo, integer knt)
SSYL01

🎯 Purpose

okay so SSYL01 tests STRSYL and STRSYL3, routines for solving the Sylvester matrix equation. The equation is:

op(A)*X + ISGN*X*op(B) = scale*C,

A and B are assumed to be in Schur canonical form, op() represents an optional transpose, and ISGN can be -1 or +1. Scale is an output less than or equal to 1, chosen to avoid overflow in X.

The test code verifies that the following residual does not exceed the provided threshold:

norm(op(A)*X + ISGN*X*op(B) - scale*C) /
    (EPS*max(norm(A),norm(B))*norm(X))

This routine complements SGET35 by testing with larger, random matrices, of which some require rescaling of X to avoid overflow.

📋 Parameters

  • THRESH — THRESH is REAL. A test will count as (the source leaves this blank, fr fr 😭) if the residual, computed as described above, exceeds THRESH.
  • NFAIL — NFAIL is INTEGER array, dimension (3).
    • NFAIL(1) = No. of times residual STRSYL exceeds threshold THRESH
    • NFAIL(2) = No. of times residual STRSYL3 exceeds threshold THRESH
    • NFAIL(3) = No. of times STRSYL3 and STRSYL deviate
  • RMAX — RMAX is REAL, dimension (2).
    • RMAX(1) = Value of the largest test ratio of STRSYL
    • RMAX(2) = Value of the largest test ratio of STRSYL3
  • NINFO — NINFO is INTEGER array, dimension (2).
    • NINFO(1) = No. of times STRSYL returns an expected INFO
    • NINFO(2) = No. of times STRSYL3 returns an expected INFO
  • KNT — KNT is INTEGER. Total number of examples tested.

Definition at line 88 of file ssyl01.f.

🌈 Author 🌈

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that’s the whole page, bestie — footer says LAPACK Version 3.12.0 and the footer path is /home/abui...IG/ssyl01.f(3). No separate date is listed, so I’m not inventing one. bye 💅✨

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