[Octave-bug-tracker] [bug #50553] eps with imaginary argument gives wrong value

[Ceral Paquet]

URL:
  <http://savannah.gnu.org/bugs/?50553>

                 Summary: eps with imaginary argument gives wrong value
                 Project: GNU Octave
            Submitted by: octavebugs
            Submitted on: Wed 15 Mar 2017 09:27:34 PM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.1
        Operating System: GNU/Linux

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Details:

MATLAB:

>> clear all
>> eps(0)
ans =
  4.9407e-324

>> eps(1)
ans =
   2.2204e-16

>> eps(i)
ans =
   2.2204e-16

>> eps(1+i)
ans =
   2.2204e-16

>> eps(1e9+i)
ans =
   1.1921e-07

>> eps(1e9i)
ans =
   1.1921e-07

>> eps(1e9+1e9i)
ans =
   2.3842e-07

>> eps(abs(1e9+1e9i))
ans =
   2.3842e-07



Octave 4.2.1

>> clear all
>> eps(0)
ans =   4.9407e-324

>> eps(1)
ans =    2.2204e-16

>> eps(i)
ans =   4.9407e-324

>> eps(1+i)
ans =    2.2204e-16

>> eps(1e9+i)
ans =    1.1921e-07

>> eps(1e9i)
ans =   4.9407e-324

>> eps(1e9+1e9i)
ans =    1.1921e-07

>> eps(abs(1e9+1e9i))
ans =    2.3842e-07


Short story: MATLAB eps() function seems to be based on abs(arg) whereas
Octave only looks at real(arg).

Fix: need to take abs() of argument to eps() function.




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