R/ParrConstraint.R

In DiceOptim: Kriging-Based Optimization for Computer Experiments

##' Strongly multimdoal constraint function from Parr et al. (standardized version)
##' @title 2D constraint function
##' @param x a 2-dimensional vector or a two-column matrix specifying the location(s) where the function
##' is to be evaluated.
##' @return A scalar
##' @export
##' @examples
##' n.grid <- 20
##' x.grid <- y.grid <- seq(0,1,length=n.grid)
##' design.grid <- expand.grid(x.grid, y.grid)
##' response.grid <- apply(design.grid, 1, ParrConstraint)
##' z.grid <- matrix(response.grid, n.grid, n.grid)
##' contour(x.grid,y.grid,z.grid,40)
##' title("Parr constraint function")
##' 
ParrConstraint <- function(x){
  # Constraint function from Parr et al. (standardized version)
  #--------------------------------------------
  # Dimension: n = 2
  
  if(is.null(dim(x))){
    x <- matrix(x, 1) 
  }
  
  x1 <- 2 * x[,1] - 1
  x2 <- 2 * x[,2] - 1
  
  g <- (4-2.1*x1^2+1/3*x1^4)*x1^2 + x1*x2 + (-4+4*x2^2)*x2^2+3*sin(6*(1-x1)) + 3*sin(6*(1-x2 ))
  
  return(-g)
}