code: private DoubleMatrix1D rDual(DoubleMatrix1D X, DoubleMatrix1D V, DoubleMatrix1D gradX) {
  		if(getA()==null){
  			return gradX;
  		}
  		//return getAT().zMult(V, gradX.copy(), 1., 1, false);
  		return ColtUtils.zMult(getAT(), V, gradX, 1);
  	}
docs: rDual(x,v) := gradF(X)+[A]T*V (p 532)