Gurobi in Java - How can I add two Expression?
Ongoing
Hello,
I declare a new expression such as GRBQuadExpr[ ] ObjExpr = new GRBQuadExpr[size];
I have another two expressions such as GRBLinExpr LinObjExpr and GRBQuadExpr QuadObjExpr.
for ( count=0; count<size; count++){
ObjExpr[count] = LinObjExpr + QuadObjExpr
}
This summation is wrong. In Cplex there is a built-in function, model.sum, to add expressions. Is there any built-in function in Gurobi?
Thank you in advance.
-
Official comment
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Hi,
you could use the add() function as
ObjExpr[count].add(LinObjExpr);
ObjExpr[count].add(QuadObjExpr);Does this work for you?
Best regards,
Jaromił0 -
Hi Jaromil,
How do you define ObjExpr in this code? I wrote the code and defined ObjExpr as GRBQuadExpr[ ] but gives error?
Thank you in advance
Best regards,
Fulya
0 -
Dear Fulya,
What kind of error do you get?
Here is an example code:
GRBLinExpr l1 = new GRBLinExpr();
l1.addTerm(1.0, x); // adding 1.0 * x to l1 where x is a GRBVar
GRBQuadExpr q1 = new GRBQuadExpr();
q1.addTerm(1.0, x, y); // adding 1.0 * x * y to q1 where x and y are GRBVar
GRBQuadExpr obj = new GRBQuadExpr();
obj.add(l1); // adding GRBLinExpr to obj
obj.add(q1); // adding GRBQuadExpr to objDoes this help?
Best regards,
Jaromił0 -
Dear Jaromil,
The error is NullPointerException. The error line is shown in
GRBQuadExpr[] objExpr = new GRBQuadExpr[sizeOfTerm];
GRBQuadExpr Sum = new GRBQuadExpr(); // yeni Ekledim
GRBLinExpr linearCoeff = new GRBLinExpr();
GRBQuadExpr quadCoeff = new GRBQuadExpr();
for (Entry<Integer, Map<String, HourlySegmentNewGurobi>> entry : hourlySegments.entrySet()) {
period = entry.getKey();
for (String segmentId : hourlySegments.get(period).keySet()) {
linearCoeff = setLinearCoeffOfHourly(hourlySegments.get(period).get(segmentId),
model, hourlyVars.get(segmentId));
quadCoeff = setQuadraticCoeffOfHourly(hourlySegments.get(period).get(segmentId), model,
hourlyVars.get(segmentId));
objExpr[count].add(linearCoeff); // This line
objExpr[count].add(quadCoeff);
Sum.add(coeffsOfHourly[count]);
count++;
}
}Best Regards,
Thank you
0 -
Dear Fulya,
It seems like the \(\texttt{linearCoeff}\) object you calculate via your \(\texttt{setLinearCoeffOfHourly}\) function is a \(\texttt{NullPointer}\). You could check this by
if (linearCoeff == null){
System.out.println("Error: linearCoeff is a NullPointer");
}Best regards,
Jaromił0 -
Dear Jaromil,
I wrote after this code
linearCoeff = setLinearCoeffOfHourly(hourlySegments.get(period).get(segmentId),
model, hourlyVars.get(segmentId));and checked it but the code do not give this error message.
Best Regards,
Fulya
0 -
Dear Fulya,
Could you post the whole \(\texttt{NullPointerException}\) error message you are getting?
Best regards,
Jaromił0 -
Dear Jaromil,
The error message such that
Exception in thread "main" java.lang.NullPointerException
After that shows the places:
at ....ObjectiveFunctionNewGurobi.setExprForHourly(ObjectiveFunctionNewGurobi.java:117)
at ....ObjectiveFunctionNewGurobi.setQuadratic(ObjectiveFunctionNewGurobi.java:42)
at ....SolverNewGurobi.setupModel(SolverNewGurobi.java:363)
at ....SolverNewGurobi.<init>(SolverNewGurobi.java:76)
at ....OptimizationEngineNewGurobi.solvePreProblem(OptimizationEngineNewGurobi.java:191)
at ....OptimizationEngineNewGurobi.run(OptimizationEngineNewGurobi.java:131)
at ....Main.runThroughFile(Main.java:265)
at ....Main.main(Main.java:95)0 -
Dear Fulya,
The error message indicates that the error comes from the \(\texttt{setExprForHourly}\) function found in file \(\texttt{ObjectiveFuncitonNewGurobi.java}\) at line 117. Please try to fix the code therein to avoid the NullPointerException.
Best regards,
Jaromił0
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