ask step by step levenberg-marquardt in java

Question

I'm trying to write levenberg marquardt in Java, here's my code:

    while (iter <= 10 || mse < 0.0001) {
        call.calc_jacobian(ff, trainlm, input, akt1, akt2, w, x, t);
        double[][] jacobian = trainlm.ret_jacob();
        double[][] error = trainlm.ret_err();
        mse = trainlm.ret_mse() / 4;
        mse_all[iter] = mse;
        test: for (int m = 0; m <= 5; m++) {
            upb.koreksi_w(miu, hidden, jacobian, error, w);
            double[][] w_new = upb.ret_upw();
            call.test_ff(ff, trainlm, input, akt1, akt2, w_new, x, t);
            double mse2 = trainlm.ret_mse() / 4;
            if (mse2 < mse || m == 5) {
                miu = miu / beta;
                w_skrg = w_baru;
                iter++;
                break test;
            } else {
                miu = miu * beta;
            }
        }
    }

The function calc_jacobian is a function I use to compute feed-forward and back-propagate operation to calculate the value of Jacobian. The function koreksi_w use to update new weight using Jacobian, error, miu, and actual weight, it will give a new weight and test_ff calculate feedforward to get mse value.

My problem is that when I try to run those code, the value of mse doesn't decrease, so I use trainlm function in matlab to run with the same input & weight, to prove that input & wight isn't the problem and in matlab , the mse decrease.

Answer 1

I don't understand your piece of code, but are you sure it is Integer division that you want when you do :

mse = trainlm.ret_mse() / 4;  //OR:
double mse2 = trainlm.ret_mse() / 4;

As you expect a double, I would suggest a cast or something like so :

double mse2 = trainlm.ret_mse() / (double)4; //OR:
double mse2 = trainlm.ret_mse() / 4.0;

Check also miu = miu / beta; (is beta a double ?)

I suspect MathLab does floating point division where java doesn't...