[Coin-discuss] AMPL driver for COIN

[Kendall Bailey]

Thank you for the feedback.

On 3/9/06, Robert Fourer <4er at iems.northwestern.edu> wrote:
>
> the output should be just a several-line status report that is passed
> back to AMPL at the front of the solution file and echoed to the user:
>
>    ampl: option solver loqo;
>    ampl: solve;
>    LOQO 6.07: optimal solution (16 QP iterations, 16 evaluations)
>    primal objective 514521.7101
>      dual objective 514521.7153
>    ampl:
>
I don't have the output quite right yet.  Not all OSI solvers are
responding to the message handler the same.


> The solver's non-default options should be supported as much as possible by the
> AMPL driver.  Simple options are typically passed through an AMPL option whose

This is where most of the remaining work lies.  But I have a framework
in place to capture the requested options.  I'm using the amplsolver.a
library as much as possible.

> Options that require potentially a number assigned to each variable or each
> constraint are handled by defining new AMPL suffixes.  For example
> Trans["ABC","DEFG"].priority might be the MIP branching priority for the
> variable Trans["ABC","DEFG"], set by an assignment statement prior to solving.

I don't understand this part.  I did read about priorities, but
haven't implemented them yet.

>
> By default AMPL passes the current values of the variables to the solver, and

I've seen this in other drivers.  It should be easy to do, once I
figure out how to do so via the OSI.

> they should be used by the solver where appropriate.  There is also a mechanism
> for passing variables' statuses between AMPL and solvers, for example in the
> case of a simplex method that can be passed a starting basis and can return an
> optimal one.

I haven't picked up on this mechanism yet.  I've been using the
lp_solve driver for an example.  I'll keep my eyes open.


> P.S.: Independently of this I am working with Kipp Martin and Jun Ma to try to
> develop a single standard for representation of optimization problem instances.
> The library for using the standard will be open source contributed to COIN.
> When such a standard is adopted by many developers of modeling language systems
> (not just AMPL), there should be considerably fewer drivers that need to be
> written.
>

I look forward to it.  Thank you.

Kendall