docs: private void computeGradientAndHessian(DMatrixRMaj param  )
      {
          // residuals = f(x) - y
          function.compute(param, residuals);
  
          computeNumericalJacobian(param,jacobian);
  
          CommonOps_DDRM.multTransA(jacobian, residuals, g);
          CommonOps_DDRM.multTransA(jacobian, jacobian,  H);
  
          CommonOps_DDRM.extractDiag(H,Hdiag);
      }