On Nov 27, 2011, at 12:24 PM, Yoji Imashuku wrote:
In my code(C++), I use try/catch to catch exceptions, and as you say
COBYLA does not print anything.
I debugged the code to determine the reason for the exception and
found
"cobyla: rounding errors are becoming damaging."
Re-reading your description, I'm confused. Are you saying that it
*doesn't* print anything? But then what do you mean by that this is
the "reason for the exception?"
Note that if COBYLA fails because of roundoff errors at that point in
the code, it returns NLOPT_FAILURE, which gets passed back to the
user. But in the C++ interface (nlopt.hpp) that return code causes it
to throw a std::runtime_error exception, as documented in the manual.
Do you mean that you got a std::runtime_error exception, and you
tracked back the NLOPT_FAILURE result to the same lines of code as
those in COBYLA which print the "roundoff errors becoming damaging"
error? If so, that may not be a bug; it may be the expected behavior
if you are asking COBLYA to try to converge to greater accuracy than
machine precision allows.
(I should probably return ROUNDOFF_LIMITED instead of NLOPT_FAILURE in
that particular case, which will throw an nlopt::roundoff_limited
exception in the C++ interface).
Steven
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