how to use dtw-loss to fit a curve?

[visionlyx]

hello,
I tried to fit a curve (discrete points) using Soft-DTW-Loss as a loss function. But the loss does not converge to the exact result in the end. Is there something wrong with the way I am using it?
The code is as follows:

if name == "main":

batch_size = 1
len_x = 15
len_predict = 10
dims = 1

device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")

x = torch.unsqueeze(torch.linspace(1, 4, steps=len_x, requires_grad=True), dim=0)
y = x ** 2
y = y.view(1, len_x, 1)
x = x.view(1, len_x, 1)

#(batch,length,dims)---->(1,15,2)
truth_points = torch.cat((y, x), dim=2).cuda()

#(1,20)
input = torch.unsqueeze(torch.linspace(1, 4, steps=len_predict*2, requires_grad=True), dim=0).cuda()


class testNN(torch.nn.Module):
    def __init__(self):
        super(testNN, self).__init__()
        self.layer = nn.Sequential(
            nn.Linear(20, 50),
            nn.ReLU(),
            nn.Linear(50, 200),
            nn.ReLU(),
            nn.Linear(200, 50),
            nn.ReLU(),
            nn.Linear(50, 20),
            nn.ReLU(),
        )
    def forward(self, x):
        x = self.layer(x)
        return x


test = testNN()
test = test.to(device)

loss_function = SoftDTW(use_cuda=True, gamma=0.01, normalize=False)
optimizer = torch.optim.Adam(test.parameters(), lr=0.01)


for epoch in range(1000):


    predict = test(input)
    #(1,20) reshape to (1,10,2)
    predict = predict.reshape(1, len_predict, 2)
    loss = loss_function(predict, truth_points)
    optimizer.zero_grad()
    loss.mean().backward(retain_graph=True)
    optimizer.step()


    if epoch % 10 == 0:
        print("epoch : %d | loss : %f" % (epoch, loss))
        plt_predict = predict.cpu().detach().numpy()
        # print(plt_predict)
        plt_predict = plt_predict.reshape(1, len_predict, 2)
        print(plt_predict[0, :, 0])
        print(plt_predict[0, :, 1])