TESTING/EIG/ssyl01.f(3)

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✨ NAME ✨

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, the routines for solving the Sylvester matrix equation:

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 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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