[Cbc] Two questions on Cbc Solver with AMPL

[Sam Mathew]

Hi Feng,

The answer to your 2nd question - you can set it using the ratio parameter,
e.g.,

cbc ratio 0.005 solve

This will mean that the solver solves until the ratio (actually gap ratio)
between the current MIP solution and the LP solution is 0.005. You can set
it to an appropriate value.

Best regards,
Sam

On 25 September 2017 at 17:40, Giacomo Nannicini <giacomo.n at gmail.com>
wrote:

> Feng,
> I believe you need to compile with the ASL solver, otherwise CBC will not
> have an AMPL interface. Look into ThirdParty/ASL.
>
> You can probably also get binaries directly from the AMPL website, in the
> open-source solver section.
>
> Giacomo
>
> On Sep 24, 2017 10:38 PM, "Feng Gao" <mangotree.gf at gmail.com> wrote:
>
> Dear Cbc Users:
>
>       I have two questions regarding to Cbc Solver with AMPL. Please help.
>
> 1. I use AMPL + Cbc solve to run a case, however, AMPL issued an error
> message "Unable to open a file" where a solution is located. I compiled the
> Cbc solver using VS and the solver is working fine in a stand-alone mode.
>
> ------------------------------------------------------------
> ------------------------------------------------------------
> ---------------------------------
> ampl: solve
> ampl? ;
> Welcome to the CBC MILP Solver
> Version: 2.9.9
> Build Date: Sep 19 2017
>
> command line - C:\COIN\Cbc\Cbc\MSVisualStudio\v10\x64-v100-Release\cbc.exe
> C:\Users\Feng\AppData\Local\Temp\at2596 -AMPL (default strategy 1)
> Unable to open file C:\Users\Feng\AppData\Local\Temp\at2596
> No match for AMPL - ? for list of commands
> Total time (CPU seconds):       0.00   (Wallclock seconds):       0.00
>
> Error executing "solve" command:
> can't open C:\Users\Feng\AppData\Local\Temp\at2596.sol
> ------------------------------------------------------------
> ------------------------------------------------------------
> ---------------------------------
>
> 2. How to set a "MIP GAP" termination criteria in Cbc solver command line.
> The manuals only provide a time limit or the maximal number of iterations
> termination criteria though.
>
> Thank you very much,
>
> Feng
>
>
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