Originally posted by: Washout

Hi all,
I am writing some code using the Java API for Cplex 12.3 for the first time and I am having problems in constructing the objective function.
It should look something like:
Sum(for some Trains t)((arrivalTime(t) - departureTime(t) - optimalTravelTime)/optimalTravelTime)

But I am getting an error :
" bad operand types for binary operator '-'
obj = model.sum(obj,(arrtrainIndexdestLoc - deptrainIndexinitialLoc - optimumTravelTime)/(double)optimumTravelTime);
first type: IloIntVar
second type: IloIntVar"

Here is a snippet of my code

public 

void addObjectiveFunction(IloModeler model, IloIntVar[][] arr, IloIntVar[][] dep) 

throws IloException 
{ 

try
{ IloNumExpr obj = model.numExpr(); ArrayList<Train> newTrains = rw.getNewTrains(); 

for(

int i = 0; i < newTrains.size(); i++) 
{ Train tr = newTrains.get(i); 

int trainIndex = tr.getID(); 

int initialLoc = 0;     
// for down trains, the index of the initial location in the journey 

int destLoc = rw.getNumberStations() - 1;   
// ID of the last station in the railway 

int optimumTravelTime = rw.getDownTravelTime(); 

if (tr.isUpTrain()) 
{   
// reverse applies for trains in UP direction initialLoc = rw.getNumberStations() - 1; destLoc = 0; optimumTravelTime = rw.getUpTravelTime(); 
} obj = model.sum(obj,(arr[trainIndex][destLoc] - dep[trainIndex][initialLoc] - optimumTravelTime)/(

double)optimumTravelTime); 
} 
}

catch (IloException e)
{ System.out.println(
"Error in creating objective function - exception: " + e); 
} 
}

How do I construct each term properly?
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: Washout

I really should have looked more closely on the forum boards before posting - apologies. I believe I have fixed the problem with the modification of the line of code

obj = model.sum(obj,model.prod(model.diff(arr[trainIndex][destLoc],(model.diff(dep[trainIndex][initialLoc], optimumTravelTime))),(1.0/optimumTravelTime)));

I was so caught up on how to implement the division that I didnt think of the obvious - use the .prod() method and the reciprocal of my constant. Just starting out with CPLEX and it's API so be kind to this bonehead =)
#CPLEXOptimizers
#DecisionOptimization