# Usage of nloptLBFGS - interpret error
**URL:** https://community.freefem.org/t/usage-of-nloptlbfgs-interpret-error/408
**Category:** General Discussion
**Created:** [May 13, 2020, 7:56pm UTC](https://community.freefem.org/t/usage-of-nloptlbfgs-interpret-error/408 "2020-05-13T19:56:47Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)
#### Post date: [May 13, 2020, 7:56pm UTC](https://community.freefem.org/t/usage-of-nloptlbfgs-interpret-error/408/1 "2020-05-13T19:56:47Z")
Hello, I want to use nloptLBFGS for an optimization problem. I managed to get a minimal test running, but when I try to apply the same syntax to the problem of interest I get the error below. It talks about a macro error, but I used “func” to define the gradient.
the line where the optimizer is called looks like:
`nloptLBFGS(J,u[],grad=GradJ);`
The error report is given below:
```
nloptLBFGS(J,u[],grad= we waiting for a '('
current line = 109
Compile error : err macro
line number :109, =
error Compile error : err macro
line number :109, =
code = 1 mpirank: 0
```
* * *
On the other hand, the following example seems to work:
```
load "ff-NLopt"
func real J(real[int] &v){
real[int] ve = v.*v;
return ve.sum;
}
func real[int] GradJ(real[int] &v){
real[int] res = 2*v;
return v;
}
real[int] x0 = [1.1,2,-1];
real mm = nloptLBFGS(J,x0,grad=GradJ);
cout << "Minimum: " << mm ;
cout << x0 <
### Author:  [@BeniaminBogosel](https://community.freefem.org/u/BeniaminBogosel)
#### Post date: [May 13, 2020, 10:16pm UTC](https://community.freefem.org/t/usage-of-nloptlbfgs-interpret-error/408/2 "2020-05-13T22:16:17Z")
Sorry for bothering you… I found the solution. It turns out I defined a macro named `grad` before, so when calling the option `grad=GradJ` FreeFem tried to replace the macro.
Best regards,
Beniamin