[Octave-bug-tracker] [bug #53991] Octave crashes using fsolve when x0 is a stationary point

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?53991>

                 Summary: Octave crashes using fsolve when x0 is a stationary
point
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Sun 27 May 2018 11:23:35 AM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error
                  Status: None
             Assigned to: None
         Originator Name: Stefano Toro
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.0
        Operating System: Microsoft Windows

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Details:

Trying to solve equation det (B(lam)) = 0 for lam, if starting point lam0 = 0,
Octave crashes without error or warning.
If lam0 = 0.1, solution found correctly.

Here the script, with a plot of B vs. lam:


mu = 0;

A = @(lam) [0 1 0 0; 0 0 1 0; 0 0 0 1; mu^2 0 -lam^2 0];
C = [1 0 0 0; 0 0 1 0];
B = @(lam) [C*expm(A(lam)*0); C*expm(A(lam)*1)];
detB = @(lam) det(B(lam));

lam0 = 0;
lcrit = fsolve (detB, lam0);

lambda = 0:0.01:4*pi;
for j=1:length(lambda)
  d(j) = detB(lambda(j));
end

plot(lambda,d)
grid on





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File Attachments:


-------------------------------------------------------
Date: Sun 27 May 2018 11:23:35 AM UTC  Name: B_vs_lam.ps  Size: 185KiB   By:
None

<http://savannah.gnu.org/bugs/download.php?file_id=44227>

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