CSYL01(3)

📦 version 3.12.0, in opensuse-leap 16.0

Hey bestie 💖 welcome to csyl01.f(3) from the Library Functions Manual — this is the whole page for CSYL01, a LAPACK testing subroutine, and it's lowkey iconic.

💖 NAME 💖

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/EIG/csyl01.f

That's the NAME, bestie — literally the full file path. Full-path main character energy, no cap ✨.

🦋 SYNOPSIS 🦋

🫶 Functions/Subroutines 🫶

subroutine CSYL01 (thresh, nfail, rmax, ninfo, knt)
    CSYL01

🧚 Function/Subroutine Documentation 🧚

subroutine CSYL01 (real thresh, integer, dimension( 3 ) nfail, real,
    dimension( 2 ) rmax, integer, dimension( 2 ) ninfo, integer knt)
    CSYL01

🌸 Purpose 🌸

Okay so CSYL01 tests CTRSYL and CTRSYL3, the routines for solving the Sylvester matrix equation:

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

where op(A) and op(B) are both upper triangular form, op() represents an optional conjugate 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 CGET35 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 if the residual, computed as described above, exceeds THRESH.

NFAIL

NFAIL is INTEGER array, dimension (3).

  • NFAIL(1) = No. of times residual CTRSYL exceeds threshold THRESH
  • NFAIL(2) = No. of times residual CTRSYL3 exceeds threshold THRESH
  • NFAIL(3) = No. of times CTRSYL3 and CTRSYL deviate

RMAX

RMAX is DOUBLE PRECISION array, dimension (2).

The signature above says real for rmax, and this parameter blurb says DOUBLE PRECISION — I'm just reporting the source, bestie, not fixing it 🙈.
  • RMAX(1) = Value of the largest test ratio of CTRSYL
  • RMAX(2) = Value of the largest test ratio of CTRSYL3

NINFO

NINFO is INTEGER array, dimension (2).

  • NINFO(1) = No. of times CTRSYL where INFO is nonzero
  • NINFO(2) = No. of times CTRSYL3 where INFO is nonzero

KNT

KNT is INTEGER.

Total number of examples tested 👑.

Definition at line 88 of file csyl01.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

LAPACK Version 3.12.0, footer file stamp /home/abui...IG/csyl01.f(3), and the footer has no date printed — mwah 💋✨ stay slay, bestie 🫶

📦 where this page comes from