topic Re: OPTMODEL - Fix stement in Mathematical Optimization, Discrete-Event Simulation, and OR

OPTMODEL - Fix stement

Prabhavanth — Fri, 03 Mar 2017 10:19:25 GMT

Could anyone please explain what difference does a fix statement make in the optmodel procedure?

Thanks in advance.

Re: OPTMODEL - Fix stement

user24feb — Fri, 03 Mar 2017 10:48:36 GMT

It sets/fixes a variable to a certain value.

Exactly as in:

proc optmodel;
      var x{1..10};
      fix x = 0;
      fix x[10] = 1;

From: http://support.sas.com/documentation/cdl/en/ormpug/66851/HTML/default/viewer.htm#ormpug_optmodel_syntax11.htm

Re: OPTMODEL - Fix stement

Prabhavanth — Fri, 03 Mar 2017 10:53:22 GMT

Thanks for the reply.

But, what's the diffrence between the following two programs?

Proc optmodel;

var x;

x=2;

put x=;

quit;

Proc optmodel;

var x;

fix x=2;

put x=;

quit;

Re: OPTMODEL - Fix stement

user24feb — Fri, 03 Mar 2017 10:58:12 GMT

Initial value vs. actually fixed value. Compare results.

Proc optmodel;
var x;
x=2;
con con: x<=10;
max obj=x;
solve;
put x=;
quit;

Proc optmodel;
var x;
fix x=2;
con con: x<=10;
max obj=x;
solve;
put x=;
quit;

Re: OPTMODEL - Fix stement

Prabhavanth — Thu, 09 Mar 2017 08:32:21 GMT

It now explains. Thanks a lot.