C++: Error code 10003 of getVar(int) to call variable

Hi all. My name is mason.

I found a strange behavior of getVar function; (1) Sometimes the function works, but (2) sometimes it doesn't.

getVar function works after model's optimize() function. Here I use the basic code "mip1_c++.cpp".

(1) I added getVar function after optimize()

// Optimize model

model.optimize();

/*********** CUSTOM CODES ************/

int x_idx = x.index();

cout<<"x's index : "<<x_idx<<endl;

GRBVarx_grbvar = model.getVar(x_idx);

cout<<"returned gurobi var's x index : "<<x_grbvar.index() <<endl;

/*************************************/

and I get the following result:

Optimal solution found (tolerance 1.00e-04)

Best objective 3.000000000000e+00, best bound 3.000000000000e+00, gap 0.0000%

x's index : 0
returned gurobi var's x index : 0
x 1
y 0
z 1
num_variable : 3
Obj: 3

(2) Now, I moved the getVar function before optimize function. Then, it throws an exception:

/*********** CUSTOM CODES ************/

int x_idx = x.index();

cout<<"x's index : "<<x_idx<<endl;

GRBVarx_grbvar = model.getVar(x_idx);

cout<<"returned gurobi var's x index : "<<x_grbvar.index() <<endl;

/*************************************/

// Optimize model

model.optimize();

Scanning dependencies of target gurobi-template

[ 50%] Building CXX object CMakeFiles/gurobi-template.dir/mip1_c++.cpp.o

[100%] Linking CXX executable gurobi-template

[100%] Built target gurobi-template

Academic license - for non-commercial use only - expires 2021-04-21

x's index : 0

Error code = 10003

Invalid arguments

Here, what I am missing and what is wrong?? Shall you help me understand?

Official comment

Simranjit Kaur

Gurobi Staff

June 23, 2025 02:58 Edited

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Jaromił Najman

March 05, 2021 12:48

Hi,

This behavior is caused by Gurobi's lazy updates. You have to call the update function before trying to access any of the optimization objects. The optimize function automatically performs an update. You can find more information in the documentation of the UpdateMode.

Best regards,
Jaromił

CHA HWAN SONG

March 05, 2021 12:50

Thanks a lot for your prompt answer!!

Sincerely,

Mason

C++: Error code 10003 of getVar(int) to call variable

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