Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic

yus03590 — Tue, 08 May 2018 21:18:27 GMT

Hi, I haven't used SAS in some time and so I'm somewhat rusty, and my organization will start using SAS OR soon. To prepare I've devised a practice problem for myself.

I'm optimizing a simple employee schedule and have the following constraint where each shift length must be at least 3 hours.

Assigned shifts are represented using a two dimensional array as shown below.

employee    8-9     9-10    10-11   etc
jack        0       1       1       
mark        0       0       0       
jane        1       1       1       
etc

1 means that employee is assigned to that time and 0 means they are not. The array is declared with sets (I will read in the contents of the sets, so the size is variable). Below is the declaration.

set <string> employees;
set <string> shifts;
num assignedShifts{employees, shifts}

Below is the code for the constraint.

dcl num index;
dcl num sum;
constraint shiftLength{e in employees, s in shifts}: 
*need to introduce logic to separate morning/afeternoon shift requirements;
    if assignedShifts{e, s} = 1 then do;
        *does this assignment statement work?;
        index = s;
        sum = 0;
        *need to somehow get set size to check bounderies;
        do while(assignedShifts{e, index});
            sum = sum + assignedShifts{e, index};
            index = index + 1;
        end;
        s = index;
    end;
    sum >= 3;

The logic I have devised for checking if each shift is three hours or not is to sum each consecutive assignment value until I run into a 0.

Question 1: I declare a numerical index, assign the value of s to it, increment the index variable, then re-assigned the it's value to s. Is this valid? If not then how would I accomplish this?

Question 2: The code I have will throw an "index out of bounds" error because I don't check that index is within the number of shifts. The number of shifts is variable since I read in the set. How do I check the size of the set at run time?

Question 3: Say I have another shift length constraint that only checks shifts in the afternoon. How would I set s to "start" at an nth value in set shifts (or to stop at an nth)?

Thanks for your help!

Re: Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic

RobPratt — Tue, 08 May 2018 21:23:15 GMT

Your constraint declaration should use algebraic expressions instead of programming statements. You might find this documentation example helpful as a starting point for your scheduling problem.

This book of examples is also useful.

topic Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic in Mathematical Optimization, Discrete-Event Simulation, and OR

Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic

Re: Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic