new solver: CHOCO

[pchtsp]

Good day,

The open source CHOCO solver recently released an MPS integration for input data. I wanted to test my model an came up with a lightweight integration for this solver in pulp.

I think it's nice to add a CP solver to the mix of pulp's solvers. Specially since it's open source.

It re-uses the other CMD solvers' structure. Specifically I took into account the GUROBI_CMD, CPLEX_CMD and COIN_CMD classes.

It's built over the PR I made to get solving and solution status separately. Because choco also makes a distinction between 'finding the optimal' and 'finding a solution'. Having said that, if the other change is not considered important enough or desirable to pulp I could include this solver on top of the master branch directly without this distinction.

The solver is built in java so it needs java installed to work, which I care to check. For the time being, for it to work it needs to have java in the PATH and the user needs to give the absolute path to the jar binary. The binary needs to be built from sources (for now, since it's a new version) but it will be available for download soon, according to the developers.

For more information, see the following:

• The MPS api
• The ticket in choco

If you have any questions, comments or changes, I'll be glad to discuss them!

Franco

[stumitchell]

Great news I will try and look at this over Easter and hopefully do a release

[pchtsp]

OK ! Now that I think of it, we could package the jar file inside pulp too. Just like it is done with CBC...

…

On Tue, Mar 27, 2018, 23:46 Stuart Mitchell ***@***.***> wrote: Great news I will try and look at this over Easter and hopefully do a release — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#169 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFNM8xwgSJJuE15jRCHVDtIw63Pxg5X_ks5tirNCgaJpZM4S9Du3> .

[pchtsp]

Ok, changes done. I still need to understand how to configure the running of the tests to be done with the PULP_CHOCO_CMD solver too.

[stumitchell]

you need to change this line

https://github.com/coin-or/pulp/blob/master/src/pulp/pulp.py#L2277

[pchtsp]

Nice, thanks. Now that I see that tests are failing I can go to bed at ease. I'll take a look tomorrow, I hope.

[pchtsp]

quick summary of the test resuls and some analysis on them:

• pulpTest009: returns optimal instead of infeasible
• pulpTest011: gives non-optimal while thinking it's optimal.
• pulpTest012: saying optimal instead of unbounded.
• pulpTest014: get an error: unsupported operand type(s) for -: 'NoneType' and 'int'
• pulpTest030: no relaxation, obviously.
• pulpTest123: choco crashes instead of saying it's unbounded.

I guess I'll send the obviusly incorrect (009, 011) to the choco team via the mps so they can check them out.
For unbounded (012, 123) I think there's no support for it, although I can always ask.
In (030) we just need to put it into the conditional.
For (014), no idea.

[pchtsp]

Current status:

remaining:

• pulpTest009: returns optimal instead of infeasible
• pulpTest011: gives non-optimal while thinking it's optimal.

"solved":

• pulpTest014: I force to write an lp in order to get the duplicate variable error as the other solvers.
• pulpTest012: saying optimal instead of unbounded => we skip the test since choco bounds all variables.
• pulpTest030: no relaxation, obviously.
• pulpTest123: choco crashes instead of saying it's unbounded => we skip the test since choco bounds all variables.

[pchtsp]

Hey Stu,
Could you please take a look at the PR now? I think it is now in a position to be working correctly.

thanks!

Franco

[stumitchell]

Hi I think I will need you to to follow this process re contribution agreements https://www.coin-or.org/contributing/code/

[pchtsp]

Hello Stuart, you mean signing the CSRO? if so, should I send it to someone in particular? you by mail for example?

[stumitchell]

please follow these steps There are two common ways to submit a CSRO: - Fill out the plain text version of the CSRO <http://www.coin-or.org/management/forms/csro.txt> and “sign” it by typing your name at the bottom. Send the completed form by email to secretary@coin-or.org - Print a hardcopy of the PDF version of the CSRO <http://www.coin-or.org/management/forms/csro.pdf>, fill it out and sign it, and email a scan to secretary@coin-or.org and cc me Stuart Mitchell PhD Engineering Science Extraordinary Freelance Programmer and Optimisation Guru www.stuartmitchell.com

…

On Thu, Oct 25, 2018 at 10:32 PM pchtsp ***@***.***> wrote: Hello Stuart, you mean signing the CSRO? if so, should I send it to someone in particular? you by mail for example? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#169 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAtEWa0kAhfU91XoqzaL16SfHWIHWhQ1ks5uoYUtgaJpZM4S9Du3> .

[pchtsp]

OK done! On Fri, 26 Oct 2018, 01:14 Stuart Mitchell, <notifications@github.com> wrote:

…

please follow these steps There are two common ways to submit a CSRO: - Fill out the plain text version of the CSRO <http://www.coin-or.org/management/forms/csro.txt> and “sign” it by typing your name at the bottom. Send the completed form by email to ***@***.*** - Print a hardcopy of the PDF version of the CSRO <http://www.coin-or.org/management/forms/csro.pdf>, fill it out and sign it, and email a scan to ***@***.*** and cc me Stuart Mitchell PhD Engineering Science Extraordinary Freelance Programmer and Optimisation Guru www.stuartmitchell.com On Thu, Oct 25, 2018 at 10:32 PM pchtsp ***@***.***> wrote: > Hello Stuart, you mean signing the CSRO? if so, should I send it to > someone in particular? you by mail for example? > > — > You are receiving this because you commented. > Reply to this email directly, view it on GitHub > <#169 (comment)>, or mute > the thread > < https://github.com/notifications/unsubscribe-auth/AAtEWa0kAhfU91XoqzaL16SfHWIHWhQ1ks5uoYUtgaJpZM4S9Du3 > > . > — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#169 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFNM80zHsPZm6fGc66aEJ-1_2cu4AvCxks5uokW-gaJpZM4S9Du3> .

[pchtsp]

Hey Stu, at the end are you thinking on merging this PR?

I'm thinking on adding mip start support for CPLEX_CMD and CBC but I don't really want to be having a whole bunch of different independent branches in my fork just so I can have independent PRs.

What do you think?

Franco

[stumitchell]

Sorry to get to this so late, I'll merge if you can fix the conflicts

[pchtsp]

Ok, I'll check this today / tomorrow. I've added the solver to the repository, in a similar fashion as CBC. Is it okay?