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import numpy as np
import chainer
from chainer import optimizers
import chainer.functions as F
import chainer.links as L
import matplotlib.pyplot as plt
class MLP(chainer.Chain):
def __init__(self):
super(MLP, self).__init__(
l1=L.Linear(1, 4),
l2=L.Linear(4, 4),
l3=L.Linear(4, 1),
def __call__(self, x):
h1 = F.sigmoid(self.l1(x))
h2 = F.sigmoid(self.l2(h1))
y = F.sigmoid(self.l3(h2))
return y
class Regressor(chainer.Chain):
def __init__(self, predictor):
super(Regressor, self).__init__(predictor=predictor)
def __call__(self, x, t):
y = self.predictor(x)
self.loss = F.sum((y - t)**2)
return self.loss
if __name__ == '__main__':
m = 50
x_train = np.linspace(-1, 1, m, dtype=np.float32).reshape((m, 1))
y_train = np.abs(x_train)
model = Regressor(MLP())
optimizer = optimizers.SGD(lr=0.1)
batchsize = 5
for epoch in range(10000):
indexes = np.random.permutation(m)
sum_loss = 0.
for i in range(0, m, batchsize):
x = chainer.Variable(x_train[indexes[i: i + batchsize]])
t = chainer.Variable(y_train[indexes[i: i + batchsize]])
optimizer.update(model, x, t)
sum_loss +=
print "epoch: {0:5d}, loss: {1:.5f}".format(epoch, sum_loss)
y_hat = model.predictor(chainer.Variable(x_train))
plt.scatter(x_train, y_train, color='r')
plt.scatter(x_train,, color='b')
# plt.savefig("mlp_approximate_abs_10000.png")
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