import numpy, theano, unittest

from theano.compile.pfunc import pfunc
from theano.compile.sharedvalue import shared
from theano import tensor
from theano.tensor.nnet import sigmoid

class NNet(object):

    def __init__(self,
            input = tensor.dvector('input'),
            target = tensor.dvector('target'),
            n_input=1, n_hidden=1, n_output=1, lr=1e-3, **kw):
        super(NNet, self).__init__(**kw)

        self.input = input
        self.target = target
        self.lr = shared(lr, 'learning_rate')
        self.w1 = shared(numpy.zeros((n_hidden, n_input)), 'w1')
        self.w2 = shared(numpy.zeros((n_output, n_hidden)), 'w2')
        #print self.lr.type

        self.hidden = sigmoid(tensor.dot(self.w1, self.input))
        self.output = tensor.dot(self.w2, self.hidden)
        self.cost = tensor.sum((self.output - self.target)**2)

        self.sgd_updates = {
                    self.w1: self.w1 - self.lr * tensor.grad(self.cost, self.w1),
                    self.w2: self.w2 - self.lr * tensor.grad(self.cost, self.w2)}

        self.sgd_step = pfunc(
                params = [self.input, self.target],
                outputs = [self.output, self.cost],
                updates = self.sgd_updates)

        self.compute_output = pfunc([self.input],  self.output)

        self.output_from_hidden = pfunc([self.hidden], self.output)

class TestNnet(unittest.TestCase):

    def test_nnet(self):
        rng = numpy.random.RandomState(1827)
        data = rng.rand(10, 4)
        nnet = NNet(n_input = 3, n_hidden = 10)
        for epoch in range(3):
            mean_cost = 0
            for x in data:
                input = x[0:3]
                target = x[3:]
                output, cost = nnet.sgd_step(input, target)
                mean_cost += cost
            mean_cost /= float(len(data))
            #print 'Mean cost at epoch %s: %s' % (epoch, mean_cost)
        self.assertTrue(abs(mean_cost - 0.20588975452) < 1e-6)
        # Just call functions to make sure they do not crash.
        out = nnet.compute_output(input)
        out = nnet.output_from_hidden(numpy.ones(10))
