[Octave-bug-tracker] [bug #54952] optimset (old, new) uses empty fields from 'new'

[Olaf Till]

URL:
  <https://savannah.gnu.org/bugs/?54952>

                 Summary: optimset (old, new) uses empty fields from 'new'
                 Project: GNU Octave
            Submitted by: i7tiol
            Submitted on: Sun 04 Nov 2018 12:11:14 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: GNU/Linux

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Details:

With option structures 'old' and 'new',

optimset (old, new)

should return an option structure with all fields of 'old', set to the values
of the respective fields in 'new' if they are present and _non-empty_ in
'new'. This is so according to Matlab documentation:

options = optimset(oldopts,newopts) combines an existing options structure
oldopts with a new options structure newopts. Any parameters in newopts with
nonempty values overwrite the corresponding old parameters in oldopts.

, and it should be so according to a comment in Octaves
scripts/optimization/optimset.m:

  elseif (nargs == 2 && isstruct (varargin{1}) && isstruct (varargin{2}))
    ## Set slots in old from non-empties in new.

, but in fact Octaves optimset even uses _empty_ fields in 'new'. This makes
correct merging of defaults with given options awkward (in the optim
package).

I've checked that fixing this wouldn't affect any Octave function  under
scripts/optimization/ .




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