BookmarkSubscribeRSS Feed
🔒 This topic is solved and locked. Need further help from the community? Please sign in and ask a new question.
user24feb
Barite | Level 11

Hello,

I would appreciate help concerning the following part of SAS/OR(R) 9.3 User’s Guide: Mathematical Programming Legacy Procedures. It's about the balancing restriction of a transport problem.

con balance {i in NODES}: sum {<(i),j> in ARCS} Flow[i,j]

      - sum {<j,(i)> in ARCS} Flow[j,i] = _sd_;

num infinity = min {r in {}} r;

   /* change equality constraint to le constraint for supply nodes */

   for {i in NODES: _sd_ > 0} balance.lb = -infinity;

The mathematical reason to change to "less or equal than" is clear. What I don't get is the syntax of min {r in {}} r. Is it a constant or a variable? Are there simpler formulations?

Thanks & kind regards

1 ACCEPTED SOLUTION

Accepted Solutions
RobPratt
SAS Super FREQ

That expression is the minimum of the empty set and is a constant that is equal to the largest double-precision floating-point number (8-bytes) that is representable on your computer.  Later versions of the documentation (starting in 13.1) use instead the simpler but equivalent constant('BIG'):

SAS/OR(R) 13.1 User's Guide: Mathematical Programming Legacy Procedures

View solution in original post

5 REPLIES 5
RobPratt
SAS Super FREQ

That expression is the minimum of the empty set and is a constant that is equal to the largest double-precision floating-point number (8-bytes) that is representable on your computer.  Later versions of the documentation (starting in 13.1) use instead the simpler but equivalent constant('BIG'):

SAS/OR(R) 13.1 User's Guide: Mathematical Programming Legacy Procedures

user24feb
Barite | Level 11

And, final question, is there a reason why the netflow version was migrated to optmodel and not to optnet?

Matthew_Galati
SAS Employee

Hi user24feb - are you referring to generalized network flow, specifically?

All of the network algorithms available in OPTNET are also available in OPTMODEL. A specific solver for generalized networks is not available in either product. Generalized networks are easily solved by the standard simplex algorithms (e.g., dual simpex) available in OPTMODEL (or OPTLP).

user24feb
Barite | Level 11

I only thought that if optnet is the successor of netflow, the example on the webpage would be an optnet and not an optmodel version. Because this would mean optmodel is better in some way (and it probably is a bit more flexible).

Matthew_Galati
SAS Employee

OPTMODEL is much more flexible and expressive than OPTNET. OPTNET will use less memory than OPTMODEL (for the same type of network model).

sas-innovate-2024.png

Available on demand!

Missed SAS Innovate Las Vegas? Watch all the action for free! View the keynotes, general sessions and 22 breakouts on demand.

 

Register now!

Multiple Linear Regression in SAS

Learn how to run multiple linear regression models with and without interactions, presented by SAS user Alex Chaplin.

Find more tutorials on the SAS Users YouTube channel.

Discussion stats
  • 5 replies
  • 1174 views
  • 3 likes
  • 3 in conversation