[Vxl-users] Powell minimiser not handling return value

[<co...@we...>]

Hi there

I have found the following in VXL 1.10.0:

The "vnl_nonlinear_minimizer" class defines a virtual function "bool
report_iter()". The documentation states the following:
"Called by derived classes after each iteration. When true is returned,
minimizer should stop with code FAILED_USER_REQUEST. Derived classes can
redefine this function to make the optimizer stop when a condition is
satisfied."

The "vnl_powell" class is derived from the "vnl_nonlinear_minimizer"
class. In its implementation we see

vnl_powell.cxx:136    report_iter();

To conform to the interface defined by the "vnl_nonlinear_minimizer" base
class this should be

vnl_powell.cxx:136    if (report_iter()) return FAILED_USER_REQUEST;

The existing code works correctly only because the Powell minimizer calls
the vnl_nonlinear_minimizer implementation of report_iter(), which always
returns false. However, when one creates a class "Foo" derived from
"vnl_powell" and override the virtual "report_iter()" function, it
currently does not behave as expected because the return value is not
handled.

Regards,
  Cobus



-------------------------------------------
South Africas premier free email service - www.webmail.co.za 
------------------------------------------------------------------
For super low premiums, click here http://www.webmail.co.za/dd.pwm