How to call a member function when we applied nlopt in our program ?

Question

0.00/5 (No votes)

See more:

I tried to implement nlopt library in my program with CNonlinearOptimization class. The problem is by using a pointer to call the member function "myfunction", I got the errors because the function doesn't match with parameter of type "nlopt_func".

Here is the member function:

double CNonlinearOptimization::myfunction(unsigned n, const double *x, double *grad, void *my_constraint_data) {
	if (grad) {
		grad[0] = 2*k1*(x[0]-1);
		grad[1] = 2*k2*(x[1]-3);
		grad[2] = 2*k3*(x[2]-5);
	}

	return (k1*(x[0]-1)*(x[0]-1)+k2*(x[1]-3)*(x[1]-3)+k3*(x[2]-5)*(x[2]-5));
}

double CNonlinearOptimization::myconstraint1(unsigned n, const double *x, double *grad, void *data){
	++count;
	if (grad) {
		grad[0] = -1;		//grad[0] = d(c1)/dx1
		grad[1] = 0;		//grad[1] = d(c1)/dx2
		grad[2] = 0;		//grad[2] = d(c1)/dx3
	}
	return (0.9-(x[0]-2));
}

And the error is "myfunction" and "myconstraint1" in main function like below

int CNonlinearOptimization::main() {

	CNonlinearOptimization nonlinopt;

	double lb[2] = { -HUGE_VAL, 0 }; // lower bounds 

	double x[3] = {0,0,1};  // `*`some` `initial` `guess`*` 
	double minf; // `*`the` `minimum` `objective` `value,` `upon` `return`*`

	opt = nlopt_create(NLOPT_LD_MMA, 3); // algorithm and dimensionality 
	nlopt_set_lower_bounds(opt, lb);

	nlopt_set_min_objective(opt,myfunction, NULL);

	nlopt_add_inequality_constraint(opt, myconstraint1, NULL, 1e-8);
	
	nlopt_set_xtol_rel(opt, 1e-4);

	if (nlopt_optimize(opt, x, &minf) < 0) {
		printf("nlopt failed!\n");
	}
	else {
		printf("found minimum after %d evaluation\n", nonlinopt.count);
		printf("found minimum at f(%0.10g,%0.10g,%0.10g) = %0.10g\n", x[0], x[1], x[2], minf);
	}

	nlopt_destroy(opt);
	system("pause");
	return 0;
}

What I have tried:

I tried to make pointer

nonlinopt.myfunction

and another pointer but it doesn't look good. How can I solve it ?

Posted 28-Mar-19 6:51am

Member 13922009

Updated 28-Mar-19 7:26am

Add a Solution

Comments

Richard MacCutchan 28-Mar-19 13:05pm

What are the actual error messages?

Member 13922009 28-Mar-19 13:10pm

Here this error:

nonlinearoptimization.cpp(274): error C3867: 'CNonlinearOptimization::myfunction': function call missing argument list; use '&CNonlinearOptimization::myfunction' to create a pointer to member

nonlinearoptimization.cpp(276): error C3867: 'CNonlinearOptimization::myconstraint1': function call missing argument list; use '&CNonlinearOptimization::myconstraint1' to create a pointer to member

Richard MacCutchan 28-Mar-19 13:12pm

Well that seems clear enough.

Member 13922009 28-Mar-19 13:15pm

but when I tried it, still error

Richard MacCutchan 28-Mar-19 13:23pm

What error? Please do not assume that we can see what is displayed on your screen.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Rick York · Answer 1 · 2019-03-28T07:27:00

What I like to do when dealing with pointers to functions is to make a typedef for them. Here is one for a function used with the BeginThread call in Windows :

C++

typedef UINT( __stdcall * ThreadFunc )( PVOID );

It appears that library has one too called nlopt_func. In the documentation it shows the function has the prototype :

C++

double f(unsigned n, const double* x, double* grad, void* f_data)

The problem is that is not a prototype for a method of your class. It is a standalone function. This means you have to pass a pointer to your object through the f_data parameter. You should implement it like this :

C++

double MyFunction( unsigned n, const double *x, double *grad, void *pdata )
{
   CNonlinearOptimization * pnlo = (CNonlinearOptimization *)pdata;
   pnlo->myfunction( n, x, grad );
}

and you should remove my_constraint_data as an argument to your method, as shown in this snippet.

This same tactic should be used with mycontstraint1.