code: private DoubleMatrix1D calculateNewtonStep(DoubleMatrix2D hessX, DoubleMatrix1D gradX) throws Exception {
  		final KKTSolver kktSolver = new BasicKKTSolver();
  		if(isCheckKKTSolutionAccuracy()){
  			kktSolver.setCheckKKTSolutionAccuracy(isCheckKKTSolutionAccuracy());
  			kktSolver.setToleranceKKT(getToleranceKKT());
  		}
  		kktSolver.setHMatrix(hessX);
  		kktSolver.setGVector(gradX);
  		DoubleMatrix1D[] sol = kktSolver.solve();
  		DoubleMatrix1D step = sol[0];
  		return step;
  	}
docs: Hess.step = -Grad