Solver npopt is a nonlinear solver based on NPOPT, a nonlinear solver
by Philip E. Gill, Walter Murray and Michael A. Saunders. NPOPT is an
updated version of NPSOL and is available from Professor Gill
to people who have NPSOL; contact peg@optimal.ucsd.edu (Philip Gill)
to see about getting source for npopt.a, a library form of NPOPT.
NPSOL is available from
Stanford Business Software
2680 Bayshore Parkway, Suite 304
Mountain View, CA 94043
Phone: +1-415-962-8719
Fax: +1-415-962-1869
It is most convenient to invoke npopt with AMPL's solve command:
ampl: option solver npopt;
ampl: solve;
but npopt can also be run separately, with invocation syntax
npopt stub [-AMPL] [keywd=[value] ...]
in which stub comes from AMPL's write command. For example,
> ampl -obfoo foo.mod foo.dat
> npopt foo
demonstrates running npopt separately; the ampl invocation
writes file foo.nl (stub = "foo"), which npopt reads.
Command-line arguments to npopt either have the form
keywd=
or
keywd=value
where keywd is one of the key words described below. Alternatively,
you can invoke npopt the way AMPL's solve command does, i.e.,
npopt stub -AMPL [keywd=value ...]
where stub was specified in
ampl -obstub ...
or
ampl -ogstub...
Such an invocation causes npopt to read from stub.nl and to write stub.sol.
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Controlling npopt
-----------------
Npopt reads keywords and values from the environment (shell) variable
npopt_options and from the command line. Execute
npopt -=
for a summary of keywords that are synonyms for NPSOL keyword phrases.
You can also give NPSOL keyword phrases if you change blanks within
them to underscores and follow them with an = (equals sign).
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Sample Invocations
------------------
If you're using AMPL, just say
option solver npopt;
solve;
If you've executed, say,
ampl -objunk junk.model junk.data
then you could say
npopt junk itera=300 linesearch=1e-6
to force npopt to run for at most 300 iterations and use linesearch
tolerance 1e-6. With the Bourne shell, either of the invocations
npopt_options='iterations=300 linesearch=1e-6' npopt junk
or
npopt_options='iterations=300 linesearch=1e-6'
export npopt_options
npopt junk
would have the same effect; within AMPL, specifying
option npopt_options 'iterations=300 linesearch=1e-6', solver npopt;
solve;
would also have this effect.
The makefile assumes that npopt.a is a library built from the NPOPT
source.
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solve_result_num values
=======================
Here is a table of solve_result_num values that "npopt" can return
to an AMPL session, along with the text that appears in the associated
solve_message.
Value Message
0 optimal solution
100 first-order optimal but not converged
200 linear constraints infeasible
201 nonlinear constraints infeasible
400 major iteration limit
501 Bug: INFORM = 5
502 stuck (INFORM = 6)
503 Bug: bad objective or constraints (INFORM = 7)
504 Bug: INFORM = 8
505 Bug: invalid input parameter (INFORM = 9)
506 unexpected INFORM value
507 solution aborted
-----------------------
Questions about this stuff? Contact dmg@ampl.com (David M. Gay).