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### gc_funcnonlinear_c++.cpp

/* Copyright 2024, Gurobi Optimization, LLC

This example considers the following nonconvex nonlinear problem

minimize   sin(x) + cos(2*x) + 1
subject to  0.25*exp(x) - x <= 0
-1 <= x <= 4

We show you two approaches to solve it as a nonlinear model:

1) Set the paramter FuncNonlinear = 1 to handle all general function
constraints as true nonlinear functions.

2) Set the attribute FuncNonlinear = 1 for each general function
constraint to handle these as true nonlinear functions.
*/
#if defined (WIN32) || defined (WIN64)
#include <Windows.h>
#endif

#include "gurobi_c++.h"
using namespace std;

static void
printsol(GRBModel& m, GRBVar& x)
{
cout << "x = " << x.get(GRB_DoubleAttr_X) << endl;
cout << "Obj = " << m.get(GRB_DoubleAttr_ObjVal) << endl;
}

int
main(int argc, char* argv[])
{
try {

// Create environment

GRBEnv env = GRBEnv();

// Create a new model

GRBModel m = GRBModel(env);

// Create variables

GRBVar x     = m.addVar(-1.0, 4.0, 0.0, GRB_CONTINUOUS, "x");
GRBVar twox  = m.addVar(-2.0, 8.0, 0.0, GRB_CONTINUOUS, "twox");
GRBVar sinx  = m.addVar(-1.0, 1.0, 0.0, GRB_CONTINUOUS, "sinx");
GRBVar cos2x = m.addVar(-1.0, 1.0, 0.0, GRB_CONTINUOUS, "cos2x");
GRBVar expx  = m.addVar(0.0, GRB_INFINITY, 0.0, GRB_CONTINUOUS, "expx");

// Set objective

m.setObjective(sinx + cos2x + 1, GRB_MINIMIZE);

m.addConstr(0.25*expx - x <= 0, "l1");
m.addConstr(2*x - twox == 0, "l2");

// sinx = sin(x)
GRBGenConstr gcf1 = m.addGenConstrSin(x, sinx, "gcf1");
// cos2x = cos(twox)
GRBGenConstr gcf2 = m.addGenConstrCos(twox, cos2x, "gcf2");
// expx = exp(x)
GRBGenConstr gcf3 = m.addGenConstrExp(x, expx, "gcf3");

// Approach 1) Set FuncNonlinear parameter

m.set(GRB_IntParam_FuncNonlinear, 1);

// Optimize the model and print solution

m.optimize();
printsol(m, x);

// Restore unsolved state and reset FuncNonlinear parameter to its
// default value
m.reset();
m.set(GRB_IntParam_FuncNonlinear, 0);

// Approach 2) Set FuncNonlinear attribute for every
//             general function constraint

gcf1.set(GRB_IntAttr_FuncNonlinear, 1);
gcf2.set(GRB_IntAttr_FuncNonlinear, 1);
gcf3.set(GRB_IntAttr_FuncNonlinear, 1);

// Optimize the model and print solution

m.optimize();
printsol(m, x);

} catch(GRBException e) {
cout << "Error code = " << e.getErrorCode() << endl;
cout << e.getMessage() << endl;
} catch(...) {
cout << "Exception during optimization" << endl;
}

return 0;
}


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