BookmarkSubscribeRSS Feed
abhik_giri
Calcite | Level 5

I have a constraint which sums the nonzero elements of a sparse matrix. To do this, I am using the SLICE expression, so my constraint reads
like this:

con test{t in ASC}:sum{u in slice(<t,*>,Map)}y>=0;

Here 'Map' is a sparse matrix, with 2 mapped variables - ASC and UIN, i.e. 'Map' contains all eligible pairs of ASC and UIN.
The constraint should work like this: For each element 't' of ASC, it should check whether 't' has a corresponding value 'u' for UIN variable. If there is, then it adds y for that row.
However, when I run this constraint, I get a "Constraint is empty" error.

What am I doing wrong here/is there a better way of doing this?

3 REPLIES 3
RobPratt
SAS Super FREQ

You can write this more compactly by using an "implicit" slice:

     con test{t in ASC}: sum{<(t),u> in Map} y >= 0;

See this doc example for more discussion:

SAS/OR(R) 13.2 User's Guide: Mathematical Programming Examples

abhik_giri
Calcite | Level 5

Thanks for the link.

Somehow the constraint you gave doesn't seem to work(again a "Constraint is empty" error). But the following constraint worked(I got it from the link you gave):

con test{t in ASC}:sum{u in UIN:<u,t> in Map}y>=0;

RobPratt
SAS Super FREQ

Your latest version is not equivalent to the other two.  Instead, it should be:

     con test{t in ASC}:sum{u in UIN:<t,u> in Map}y>=0;

Also, the "Constraint is empty" message is only a NOTE and not an ERROR.  If you use the EXPAND statement, you will see that the constraint is 0 >= 0 because the sum is empty.  If you really want to avoid generating these constraints, you can use a logical condition:

     con test{t in ASC: card(slice(<t,*>,Map)) > 0}:sum{u in slice(<t,*>,Map)}y>=0;

hackathon24-white-horiz.png

The 2025 SAS Hackathon Kicks Off on June 11!

Watch the live Hackathon Kickoff to get all the essential information about the SAS Hackathon—including how to join, how to participate, and expert tips for success.

YouTube LinkedIn

Discussion stats
  • 3 replies
  • 1583 views
  • 3 likes
  • 2 in conversation