eval_f<-function(x){
return(100*(x[2]-x[1]*x[1])^2+(1-x[1])^2)
}
eval_grad_f<-function(x){
return(c(400*x[1]*x[2]-x[1]*x[1]-2*(1-x[1]),
200*(x[2]-x[1]*x[1])))
}
library(nloptr)
x0<-c(-1,2,1)
opts<-list("algorithm"="NLOPT_LD_LBFGS",
"xtol_res"=1.0e-8)
res<-nloptr(x0=x0,
eval_f=eval_f,
eval_g=eval_g,
opts=opts)