hi,
I am trying to solve the following problem

I mean I want to minimize the function f(x).
I have written the following code (without the FIX commands)
proc optmodel;
var x1, x2 , x3;
min f = x1^2 + 2*(x2^2) + 5*(x3^2) -4*x1 -20*x2 -20*x3;
/* starting point */
x1 = 0;
x2 = 0;
x3 = 0;
solve;
print x1 x2 x3 x1.dual x2.dual x3.dual;
quit;
and I get the following result

There are no values for the dual but I get the value of objective function
But when I write the same code with fix commands (as given below).
proc optmodel;
var x1, x2 , x3;
min f = x1^2 + 2*(x2^2) + 5*(x3^2) -4*x1 -20*x2 -20*x3;
/* starting point */
fix x1 = 0;
fix x2 = 0;
fix x3 = 0;
solve;
print x1 x2 x3 x1.dual x2.dual x3.dual;
quit;
then i get the following result
+
now there are no values for the 3 variables and also no value for the objective function
Sorry I dont know exactly the function of "FIX" command.
Please can you explain the purpose of "FIX" command here.
Which code should I use to solve this problem?
thanks