[Coin-ipopt] How many variables???

Carl Damon Laird claird at andrew.cmu.edu
Fri Apr 28 09:36:36 EDT 2006

AMPL has a preprocessing phase that may remove variables from the problem. 
The number returned by AMPL is the full count before any preprocessing, 
while the number reported by Ipopt is the number of variables given to the 
solver (after preprocessing).

In most cases, you can turn off the ampl preprocessing and substitution 
phase with,

option presolve 0;
option substout 0;

Hope this helps,


On Fri, 28 Apr 2006, [ISO-8859-1] Rodrigo López Negrete de la Fuente wrote:

> Hello,
> I've been trying to determine how many variables my problem has when passed
> to IPOPT. I'm using the AMPL interface by the way. IPOPT says that the
> Total number of variables..........14358
> In contrast with ampl's variable _nvars, that says that the problem has
> 36631 variables. So which is it, 14+ thousand or 36+ thousand?? Which value
> should I report?
> thanks,
> rodrigo
> --
> Rodrigo López Negrete
> http://muon.blogdns.org/~rush/

More information about the Coin-ipopt mailing list