Is there a way to save the instances generated by ecole.instance as mps file supported by PySCIPOpt

[thupchnsky]

Hi,

I am trying to save the instances generated by ecole.instance.SetCoverGenerator as mps files beacuse I need them to be used by different algorithms for fair comparison. However, I dont find the direct write out method for these instances. I know that PySCIPOpt has method like model.writeProblem("xxx.mps"). So I am wondering how should I convert the instance to pyscipopt.scip.model so I can save the files? Thanks!

[AntoinePrv]

Hello,

Model.write_problem will forward to SCIPwriteOrigProblem, and the extension is detected by SCIP, so you can

model.write_problem("my-instance.mps")

Or

model.write_problem("my-instance.lp")

...

[AntoinePrv]

Well it seems that if I am using model.write_poblem("my-instance.mps"), it complains about 'ecole.core.scip.Model' object has no attribute 'write_poblem'.

It works for me. I don't remember when we added it. Are you running the latest version of Ecole (v0.6.0)?

[thupchnsky]

I am using Python 3.8.8 with ecole 0.6.0 and pyscipopt 3.1.2. Not sure what the problem would be... I am just using the following code

import ecole
instances = ecole.instance.SetCoverGenerator(n_rows=500, n_cols=1000, density=0.05)
model = next(instances)
model.write_poblem("my-instance.mps")

[AntoinePrv]

Haha, I got the same problem in the end running the code sample! I made a typo:
write_poblem > write_problem

[AntoinePrv]

You can find the methods we currently have on ecole.scip.Model in the doc.

We don't aim to bind everything, only highly used methods, or methods not offered in PySCIPOpt.

[thupchnsky]

Thanks for the help! That was really an embrassing typo lol...