code: protected DoubleMatrix2D getHessF0(DoubleMatrix1D X) {
  		double[][] hess = request.getF0().hessian(X.toArray());
  		if(hess == FunctionsUtils.ZEROES_2D_ARRAY_PLACEHOLDER){
  			return F2.make(X.size(), X.size());
  		}else{
  			return F2.make(hess);
  		}
  	}
docs: Objective function hessian at X.