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Question of constraint in Proc Optmodel

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Frequent Contributor
Posts: 107

Question of constraint in Proc Optmodel

On SAS Proc Optmodel,

I set variable A, which is a 2*2 matrix [p,k]

And variable B, and C are both 2*1 matrix [p,k], where B and C are one particular value of k. Like A = [B,C]

For coding convenience, sometimes I used A, and sometimes I used B and C.

I may need a constraint to describe the relationship between them. A = [B, C]

How can I put it as a constraint?

Thank you!

SAS Employee
Posts: 448

Re: Question of constraint in Proc Optmodel

You can define explicit constraints, but this looks to me like a good place to instead use implicit variables:

impvar B {p in PSET} = A[p,1];

impvar C {p in PSET} = A[p,2];

Frequent Contributor
Posts: 107

Re: Question of constraint in Proc Optmodel

Thanks, I tried in this way but it seems A is a 0 matrix.

May I ask how to define specific constraint?

SAS Employee
Posts: 448

Re: Question of constraint in Proc Optmodel

I don't understand what is wrong with what you tried.  What I suggested should work no matter what values the A variables take.  If you post your code, I'll take a look.

Here's how you can define B with an explicit variable and constraint:


var B {PSET};

con Bcon {p in PSET}: B

= A[p,1];


You can do something similar for C.

Frequent Contributor
Posts: 107

Re: Question of constraint in Proc Optmodel

Sorry it seems I cannot upload a file larger than 1kb.

And below is part of my code:

var rep_size_1 {PRODUCTS, STAGES2}>=0 integer;

var rep_size_12 {PRODUCTS}>=0 integer;

var rep_size_13 {PRODUCTS}>=0 integer;

constraint c1 {p in PRODUCTS}:

                   rep_size_12

= rep_size_1 [p,1];

constraint c2 {p in PRODUCTS}:

                   rep_size_13

= rep_size_1 [p,2];

With the error message:

ERROR: The array subscript 'rep_size_1[1,1]' is invalid at line 1051 column 38.

Thanks!

SAS Employee
Posts: 448

Re: Question of constraint in Proc Optmodel

Evidently, STAGES2 does not contain 1.  In that case, you will get the same error if you use IMPVAR.

You need to use other values for k if they are not 1 and 2.

Frequent Contributor
Posts: 107

Re: Question of constraint in Proc Optmodel

Got it.

You are the best, Rob!

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