ampl-cplex: ampl timing parameter misbehaving (version issue?)

[philip....@gmail.com]

Hi there!

At my current place of employment, we sometimes use ampl to call cplex, but the server on which we do so often has a lot've competing compute-traffic, so it's hard to get clean estimates of real run-times, and I've been looking for ways to get more nearly traffic-independent measures. On the list of cplex options for ampl, I see that ampl's timing parameter has these options:

timing                 Whether to write times in seconds or "ticks" to
                       stdout or stderr: sum of
                           1 = write time in seconds to stdout
                           2 = write time in seconds to stderr
                           4 = write time in "ticks" to stdout
                           8 = write time in "ticks" to stderr
                          16 = write number of logical cores to stdout
                          32 = write number of logical cores to stderr.
                       Default = 0.

which would fit the bill perfectly; both the number of logical cores (expressed as an average-per-unit-time usage percentage of some kind, I'm assuming?)  and number of ticks would be great for us to have.

However, when I attempt to pass timing options to cplex, I get an error message indicating that timing only accepts values between 0 and 3. My suspicion is that this is because our ampl version appears to be ~5 years out of date; ampl -v at a terminal command-line prompt gives AMPL Version 20110909.

I've looked (quickly) through some of the past version updates I found for ampl and didn't see this change documented, but I was hoping someone more ampl-knowledgeable might be able to confirm for me that that's what's going on, so that I can justify requesting that we look into updating our installed ampl version.

Thank you in advance!

Best,

Philip Leclerc

Mathematical Statistician, United States Census Bureau

[Robert Fourer]

There's a log of the changes to the AMPL-CPLEX interface at http://ampl.com/netlib/ampl/solvers/cplex/changes that shows this extension to the 'timing' option as being added in 2012:

20121117
cplex.c: add zerohalfcuts to the cuts simultaneously controlled
by mipcuts. Update to CPLEX 12.5: add keywords dettimelim,
polishafter_timedet, probetimedet, seed, and tunetimedet, and extend
timing keyword to allow requesting times in platform-specific "ticks",
which CPLEX computes in an unspecified way.

Bob Fourer
am...@googleroups.com

=======

[philip....@gmail.com]

Exactly what I'd failed to find myself! Thanks for the pointer to the log of changes, and for specifically highlighting the one I needed, Bob.

Best,

Philip Leclerc

United States Census Bureau, Mathematical Statistician