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from singa import tensor
from singa.tensor import Tensor
from singa import autograd
from singa import opt
import numpy as np

if __name__ == "__main__":

    autograd.training = True

    # prepare training data in numpy array

    # generate the boundary
    f = lambda x: (5 * x + 1)
    bd_x = np.linspace(-1.0, 1, 200)
    bd_y = f(bd_x)
    # generate the training data
    x = np.random.uniform(-1, 1, 400)
    y = f(x) + 2 * np.random.randn(len(x))
    # convert training data to 2d space
    label = np.asarray([5 * a + 1 > b for (a, b) in zip(x, y)])
    data = np.array([[a, b] for (a, b) in zip(x, y)], dtype=np.float32)

    def to_categorical(y, num_classes):
        """
        Converts a class vector (integers) to binary class matrix.

        Args
            y: class vector to be converted into a matrix
                (integers from 0 to num_classes).
            num_classes: total number of classes.

        Return
            A binary matrix representation of the input.
        """
        y = np.array(y, dtype="int")
        n = y.shape[0]
        categorical = np.zeros((n, num_classes))
        categorical[np.arange(n), y] = 1
        return categorical

    label = to_categorical(label, 2).astype(np.float32)
    print("train_data_shape:", data.shape)
    print("train_label_shape:", label.shape)

    inputs = Tensor(data=data)
    target = Tensor(data=label)

    w0 = Tensor(shape=(2, 3), requires_grad=True, stores_grad=True)
    w0.gaussian(0.0, 0.1)
    b0 = Tensor(shape=(3,), requires_grad=True, stores_grad=True)
    b0.set_value(0.0)

    w1 = Tensor(shape=(3, 2), requires_grad=True, stores_grad=True)
    w1.gaussian(0.0, 0.1)
    b1 = Tensor(shape=(2,), requires_grad=True, stores_grad=True)
    b1.set_value(0.0)

    sgd = opt.SGD(0.05)
    # training process
    for i in range(1001):
        x = autograd.matmul(inputs, w0)
        x = autograd.add_bias(x, b0)
        x = autograd.relu(x)
        x = autograd.matmul(x, w1)
        x = autograd.add_bias(x, b1)
        loss = autograd.softmax_cross_entropy(x, target)
        sgd(loss)

        if i % 100 == 0:
            print("training loss = ", tensor.to_numpy(loss)[0])