I use GAMS for solving my MIP models. But I want to see in first step, first simplex table, more clearly I want to see A matrix in Ax=b formulation. Is there any way to see this matrix in GAMS?

asked 02 Dec '15, 11:45

kubi's gravatar image

kubi
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It is possible to export the matrix (jacobian for NLPs) using the option hessian or jacobian with the Convert tool. You will see something like:

alt text

If you don't know how to get this working, contact support@gams.com. They can help with the details including how to export this to Matlab etc.

link

answered 02 Dec '15, 12:27

erwin's gravatar image

erwin
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accept rate: 10%

edited 03 Dec '15, 00:01

Thank you.

(02 Dec '15, 12:56) kubi

If you mean by Simplex Table the Simplex Tableau then I do not know how this can be displayed. (I do not see how this can be of any use either. That is: I never had the urge to look at this thing.)

If you just want to see the equations that GAMS generates, you can inspect the Equation Listing in the GAMS listing file. By default it just lists 3 rows per block, but you can make this larger using OPTION LIMROW=n;

If you want to see how a model arrived in a solver, some solvers can write an LP file or MPS file of a problem generated by GAMS.

If you want to look at a BLOCKPIC of the structure of a model (some users find this useful) then there is a tool called GAMSCHK.

Erwin

link

answered 02 Dec '15, 12:00

erwin's gravatar image

erwin
40113
accept rate: 10%

Actually my model is MIP type. And I want to check whether it has total unimodularity. Therefore I need starting A matrix. Is there any other way to examine unimodularity ?

(02 Dec '15, 12:04) kubi
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Asked: 02 Dec '15, 11:45

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Last updated: 03 Dec '15, 00:01

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