[Octave-bug-tracker] [bug #59486] p variable not always defined in eigs function

[Rik]

Follow-up Comment #7, bug #59486 (project octave):

Change looks fine.  

And eps() called with an argument is actually exactly what you want.  When
called as eps (X) it gives you the machine precision around the number (X). 
When called with no argument it gives the machine precision around the default
(1).  So X*eps(1) is very much related to eps (X), but they are not always
identical.  For example,


octave:1> eps (65) - 65*eps
ans = -2.2204e-16


Not so bad, but consider a larger number


octave:7> e1 = eps (1e6)
e1 = 1.1642e-10
octave:8> e2 = 1e6*eps
e2 = 2.2204e-10
octave:9> delta = e2 - e1
delta = 1.0563e-10
octave:10> percent_change = delta / e1 * 100
percent_change = 90.735


In this case, the kluge way of calculating machine precision is of by 90%.

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