[Clp] Hello and Help to start using clp.

[Robinson Lemos]

Thank you Robert!

I will give the OSI API a try. It is what I am looking for: an API.

Thank you very much.

Robinson



2016-07-21 20:54 GMT-04:00 Lacroix, Robert <ralacroix at hydro.mb.ca>:

> Robinson,
>
>
>
> I can see why you are having a problem. The CLP user guide is falling
> apart. All the CLP example source code hosted on IBM’s web site is gone!
>
> http://www.coin-or.org/Clp/userguide/ch04.html
>
>
>
> Apart from this, I recommend using the COIN-OR Open Solver Interface (OSI)
> API. You can load the rows and columns of the LP into a CoinPackedMatrix
> then present it to the solver through the OSI API. First use Gurobi as the
> back-end solver to validate that you are correctly loading the LP into the
> matrix and getting back the answers you expect. Then after you are
> satisfied that your API usage is correct, switch the solver engine to CLP.
>
>
>
> I do not recommend using MPS files when you can use an API. If you must
> use MPS files, try to use the printed IEEE format for values.
>
> 1)      MPS is a text file format. Most numbers printed as decimal differ
> in value and precision form the internal IEEE double precision
> representation - not a good way to transfer data between iterations,
> especially on sensitive problems where tiny changes can lead to different
> solutions.
>
> 2)      Writing MPS files takes several orders of magnitude more time,
> compared to copying arrays of data in memory. Would you wait 25 minutes to
> create the MPS file for an iteration that takes only 33 seconds to solve?
> (from our experience trying this with LPs considerably smaller than the
> sparse 38000 row and 96000 column problems we formulate these days).
>
> 3)      If you use the Gurobi API only to formulate the problem and send
> it to the MPS file, then you are still using Gurobi, just not as a solver.
>
>
>
> Robert Lacroix
> Manitoba Hydro
>
>
>
> *From:* Clp [mailto:clp-bounces at coin-or.org] *On Behalf Of *Robinson Lemos
> *Sent:* Monday, July 18, 2016 10:02 AM
> *To:* clp at list.coin-or.org
> *Subject:* [Clp] Hello and Help to start using clp.
>
>
>
> Hello from Brazil.
>
>
>
> I am Robinson Lemos.
>
>
>
> First i want to apologize my English and I hope it all makes sense.
>
>
>
> I have read the tutorials at https://projects.coin-or.org/Clp, but I did
> not understand a way to read a model from memory or construct it.
>
>
>
> I want to leave gurobi and start using clp only.
>
>
>
> My deal is the following:
>
>
>
> I use an algorithm, and each iteration i need to change and solve a LP
> model some times. In the MPS way i will need to create, save and read about
> 30-600 MPS files per iteration.
>
>
>
> Is there any tutorial showing how to use the loadProblem() variations?
>
>
>
> Thank you.
>
>
>
> Robinson Lemos.
>
>
>
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>
>
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