Monday, November 9, 2009

NEOS statistics

At http://neos.mcs.anl.gov/neos/report.html you can ask for statistics of the usage of the NEOS solvers (http://neos.mcs.anl.gov/neos/).

I ran the statistics for a year and a few interesting and unexpected patterns showed up.

The top 5 solvers:

List of Solvers
Solver Name # of Submissions
KNITRO 22498
bpmpd 20185
MINOS 15932
MINTO 14769
SNOPT 12916

is dominated by NLP solvers (knitro, minos, snopt). It may be possible that some LP’s are solved with NLP solvers (I see that sometimes also happening in client models). I had to google what bpmpd was (see http://www.sztaki.hu/~meszaros/bpmpd/), and I am surprised it ended up so high. It is nice to see good old MINOS ending up prominently in the top 5.

If we look at the top 5 input formats we see:

List of Inputs
Solver Input # of Submissions
AMPL 139782
GAMS 63873
CPLEX 3251
Fortran 3176
MPS 2940

Here we see AMPL as the winner with GAMS having half the submissions. This could well be explained by having most submissions coming from educational institutions, where AMPL is most likely more popular than GAMS as its format is closer to a mathematical formulation. It is good to see that almost all submissions are done in modeling languages: users should stay away from programming languages to build models unless there are significant reasons otherwise. Also note that Fortran seems to be more popular than C (at rank 7).

List of Categories
Solver Category # of Submissions
nco 65532
milp 49524
lp 32231
minco 28732
kestrel 15474

I assume that nco means non-linear constrained optimization. This confirms that many NLP models are solved on NEOS. I would guess minco means MINLP.

I certainly would not have predicted some of these numbers!