Simple implementation of Generative Adversarial Nets using chainer

data.py

import gzip
import os

import numpy as np
import six
from six.moves.urllib import request

parent = 'http://yann.lecun.com/exdb/mnist'
train_images = 'train-images-idx3-ubyte.gz'
train_labels = 'train-labels-idx1-ubyte.gz'
test_images = 't10k-images-idx3-ubyte.gz'
test_labels = 't10k-labels-idx1-ubyte.gz'
num_train = 60000
num_test = 10000
dim = 784


def load_mnist(images, labels, num):
    data = np.zeros(num * dim, dtype=np.uint8).reshape((num, dim))
    target = np.zeros(num, dtype=np.uint8).reshape((num, ))

    with gzip.open(images, 'rb') as f_images,\
            gzip.open(labels, 'rb') as f_labels:
        f_images.read(16)
        f_labels.read(8)
        for i in six.moves.range(num):
            target[i] = ord(f_labels.read(1))
            for j in six.moves.range(dim):
                data[i, j] = ord(f_images.read(1))

    return data, target


def download_mnist_data():
    print('Downloading {:s}...'.format(train_images))
    request.urlretrieve('{:s}/{:s}'.format(parent, train_images), train_images)
    print('Done')
    print('Downloading {:s}...'.format(train_labels))
    request.urlretrieve('{:s}/{:s}'.format(parent, train_labels), train_labels)
    print('Done')
    print('Downloading {:s}...'.format(test_images))
    request.urlretrieve('{:s}/{:s}'.format(parent, test_images), test_images)
    print('Done')
    print('Downloading {:s}...'.format(test_labels))
    request.urlretrieve('{:s}/{:s}'.format(parent, test_labels), test_labels)
    print('Done')

    print('Converting training data...')
    data_train, target_train = load_mnist(train_images, train_labels,
                                          num_train)
    print('Done')
    print('Converting test data...')
    data_test, target_test = load_mnist(test_images, test_labels, num_test)
    mnist = {}
    mnist['data'] = np.append(data_train, data_test, axis=0)
    mnist['target'] = np.append(target_train, target_test, axis=0)

    print('Done')
    print('Save output...')
    with open('mnist.pkl', 'wb') as output:
        six.moves.cPickle.dump(mnist, output, -1)
    print('Done')
    print('Convert completed')


def load_mnist_data():
    if not os.path.exists('mnist.pkl'):
        download_mnist_data()
    with open('mnist.pkl', 'rb') as mnist_pickle:
        mnist = six.moves.cPickle.load(mnist_pickle)
    return mnist

train.py

import sys
import os
import logging
import argparse
import pickle
import numpy as np
from PIL import Image
import chainer
from chainer import cuda
import chainer.functions as F
import chainer.optimizers

import data


class GANModel(chainer.FunctionSet):

    n_hidden = 100

    def __init__(self):
        super(GANModel, self).__init__(
            g_fc0=F.Linear(self.n_hidden, 500),
            g_fc1=F.Linear(500, 500),
            g_fc2=F.Linear(500, 784),
            d_fc0=F.Linear(784, 240),
            d_fc1=F.Linear(240, 240),
            d_fc2=F.Linear(240, 1))

    @property
    def generators(self):
        return [self.g_fc0, self.g_fc1, self.g_fc2]

    @property
    def discriminators(self):
        return [self.d_fc0, self.d_fc1, self.d_fc2]

    def make_z(self, n):
        return 0.2 * np.asarray(
            np.random.randn(n, self.n_hidden),
            dtype=np.float32)

    def make_generator(self, z, train=True):
        h = F.dropout(F.relu(self.g_fc0(z)), train=train)
        h = F.dropout(F.relu(self.g_fc1(h)), train=train)
        return self.g_fc2(h)
        # return F.sigmoid(self.g_fc2(h))

    def make_discriminator(self, x, t, train=True):
        h = F.relu(self.d_fc0(x))
        h = F.relu(self.d_fc1(h))
        h = self.d_fc2(h)
        return F.sigmoid_cross_entropy(h, t)

    def collect_generator_parameters(self):
        parameters = (
            sum((f.parameters for f in self.generators), ()),
            sum((f.gradients for f in self.generators), ()),
        )
        return parameters

    def collect_discriminator_parameters(self):
        parameters = (
            sum((f.parameters for f in self.discriminators), ()),
            sum((f.gradients for f in self.discriminators), ()),
        )
        return parameters

    def generate(self, z_data, train=True):
        z = chainer.Variable(z_data)
        x = self.make_generator(z, train=train)
        return x.data

    def forward_xy(self, x_data, t_data):
        x = chainer.Variable(x_data)
        t = chainer.Variable(t_data)
        loss = self.make_discriminator(x, t)
        return loss

    def forward_zy(self, z_data, t_data):
        z = chainer.Variable(z_data)
        t = chainer.Variable(t_data)
        x = self.make_generator(z)
        loss = self.make_discriminator(x, t)
        return loss


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('--batch', type=int, default=50)
    parser.add_argument('--epoch', type=int, default=30)
    parser.add_argument('-g', '--gpu', type=int, default=-1)
    parser.add_argument('--display', type=int, default=100)
    parser.add_argument('--image', default='./')
    parser.add_argument('--dst', default='model.pkl')
    args = parser.parse_args()

    logging.basicConfig(
        format="%(asctime)s [%(levelname)s] %(message)s",
        level=logging.DEBUG)
    logger = logging.getLogger(__name__)

    if 0 <= args.gpu:
        cuda.init(args.gpu)

    logger.info('loading MNIST dataset...')
    mnist = data.load_mnist_data()
    mnist['data'] = mnist['data'].astype(np.float32)
    mnist['data'] /= 255
    x_train = mnist['data']

    logger.info('constructing GAN model...')
    model = GANModel()
    if 0 <= args.gpu:
        model = model.to_gpu(args.gpu)

    logger.info('initializing two optimizers...')
    g_optimizer = chainer.optimizers.Adam(alpha=-1e-5)
    g_optimizer.setup(model.collect_generator_parameters())
    d_optimizer = chainer.optimizers.Adam(alpha=1e-5)
    d_optimizer.setup(model.collect_discriminator_parameters())

    example_z = model.make_z(100)
    if 0 <= args.gpu:
        example_z = cuda.to_gpu(example_z, args.gpu)

    iteration = 0
    for epoch in xrange(1, args.epoch + 1):
        logger.info('epoch %i', epoch)

        perm = np.random.permutation(x_train.shape[0])
        sum_dloss, sum_gloss = 0.0, 0.0

        example_x = cuda.to_cpu(model.generate(example_z, train=False))
        example_x = example_x.reshape(10, 10, 28, 28).transpose([0, 2, 1, 3])
        example_x = np.clip(
            255 * example_x.reshape(280, 280), 0.0, 255.0).astype(np.uint8)
        img = Image.fromarray(example_x)
        img.save(os.path.join(args.image, "{:03}.png".format(epoch)))

        for i in xrange(0, x_train.shape[0], args.batch):
            iteration += 1
            batchsize = min(i + args.batch, x_train.shape[0]) - i

            # update discriminator
            x_batch = np.empty(
                (2 * batchsize, x_train.shape[1]), dtype=np.float32)
            t_batch = np.empty((2 * batchsize, 1), dtype=np.int32)
            z_batch = model.make_z(batchsize)
            if 0 <= args.gpu:
                z_batch = cuda.to_gpu(z_batch, args.gpu)
            x_batch[:batchsize] = cuda.to_cpu(model.generate(z_batch))
            x_batch[batchsize:] = x_train[perm[i:i + batchsize]]
            t_batch[:batchsize] = 0
            t_batch[batchsize:] = 1
            if 0 <= args.gpu:
                x_batch = cuda.to_gpu(x_batch, args.gpu)
                t_batch = cuda.to_gpu(t_batch, args.gpu)
            d_optimizer.zero_grads()
            #g_optimizer.zero_grads()
            dloss = model.forward_xy(x_batch, t_batch)
            dloss.backward()
            d_optimizer.update()

            dloss_data = float(cuda.to_cpu(dloss.data))
            sum_dloss += dloss_data * batchsize * 2

            # update generator
            z_batch = model.make_z(batchsize)
            t_batch = np.zeros((batchsize, 1), dtype=np.int32)
            if 0 <= args.gpu:
                z_batch = cuda.to_gpu(z_batch, args.gpu)
                t_batch = cuda.to_gpu(t_batch, args.gpu)
            #d_optimizer.zero_grads()
            g_optimizer.zero_grads()
            gloss = model.forward_zy(z_batch, t_batch)
            gloss.backward()
            g_optimizer.update()

            gloss_data = float(cuda.to_cpu(gloss.data))
            sum_gloss += gloss_data * batchsize

            if iteration % args.display == 0:
                logger.info(
                    'loss D:%.3e G:%.3e iter:%i',
                    dloss_data, gloss_data, iteration)

        ave_dloss = sum_dloss / (2 * x_train.shape[0])
        ave_gloss = sum_gloss / x_train.shape[0]
        logger.info(
            'train mean loss D:%.3e G:%.3e epoch:%i',
            ave_dloss, ave_gloss, epoch)

    logger.info('done. now pickling model...')
    with open(args.dst, 'wb') as fp:
        pickle.dump(model, fp)


if __name__ == "__main__":
    sys.exit(main())

Is Line 169 np.ones(*) ? This is because the generator should be trained to make the discriminator missclassify the sampled data.

@vebmaylrie Sorry for replying late.
Exactly, in order to make the discriminator missclassify the sampled data,
I set the alpha in the optimizer of the optimizer to the negative value.