main2.py

# coding: utf-8
from __future__ import division

from collections import OrderedDict
from time import time

import models
import data

import theano
import sys
import os.path

import theano.tensor as T
import numpy as np

from main import get_minibatch

MAX_EPOCHS = 50
MINIBATCH_SIZE = 128
L2_REG = 0.0
CLIPPING_THRESHOLD = 2.0
PATIENCE_EPOCHS = 1

"""
Second stage training
"""

if __name__ == "__main__":

    if len(sys.argv) > 1:
        model_name = sys.argv[1]
    else:
        sys.exit("'Model name' argument missing!")

    if len(sys.argv) > 2:
        num_hidden = int(sys.argv[2])
    else:
        sys.exit("'Hidden layer size' argument missing!")

    if len(sys.argv) > 3:
        learning_rate = float(sys.argv[3])
    else:
        sys.exit("'Learning rate' argument missing!")

    if len(sys.argv) > 4:
        stage1_model_file_name = sys.argv[4]
    else:
        sys.exit("'Stage 1 model path' argument missing!")

    model_file_name = "Model_stage2_%s_h%d_lr%s.pcl" % (model_name, num_hidden, learning_rate)

    print num_hidden, learning_rate, model_file_name

    word_vocabulary = data.read_vocabulary(data.WORD_VOCAB_FILE)
    punctuation_vocabulary = data.iterable_to_dict(data.PUNCTUATION_VOCABULARY)

    x = T.imatrix('x')
    y = T.imatrix('y')
    p = T.matrix('p')
    lr = T.scalar('lr')

    if os.path.isfile(model_file_name):
        print "Loading previous model state"

        net, state = models.load(model_file_name, MINIBATCH_SIZE, x, p)
        gsums, learning_rate, validation_ppl_history, starting_epoch, rng = state
        best_ppl = min(validation_ppl_history)

    else:
        rng = np.random
        rng.seed(1)

        print "Building model..."
        net = models.GRUstage2(
            rng=rng,
            x=x,
            minibatch_size=MINIBATCH_SIZE,
            n_hidden=num_hidden,
            x_vocabulary=word_vocabulary,
            y_vocabulary=punctuation_vocabulary,
            stage1_model_file_name=stage1_model_file_name,
            p=p
            )

        starting_epoch = 0
        best_ppl = np.inf
        validation_ppl_history = []

        gsums = [theano.shared(np.zeros_like(param.get_value(borrow=True))) for param in net.params]

    cost = net.cost(y) + L2_REG * net.L2_sqr

    gparams = T.grad(cost, net.params)
    updates = OrderedDict()

    # Compute norm of gradients
    norm = T.sqrt(T.sum(
               [T.sum(gparam ** 2) for gparam in gparams]
           ))


    # Adagrad: "Adaptive subgradient methods for online learning and stochastic optimization" (2011)
    for gparam, param, gsum in zip(gparams, net.params, gsums):
        gparam = T.switch(
            T.ge(norm, CLIPPING_THRESHOLD),
            gparam / norm * CLIPPING_THRESHOLD,
            gparam
        ) # Clipping of gradients
        updates[gsum] = gsum + (gparam ** 2)
        updates[param] = param - lr * (gparam / (T.sqrt(updates[gsum] + 1e-6)))

    train_model = theano.function(
        inputs=[x, p, y, lr],
        outputs=cost,
        updates=updates
    )

    validate_model = theano.function(
        inputs=[x, p, y],
        outputs=net.cost(y)
    )

    print "Training..."
    for epoch in range(starting_epoch, MAX_EPOCHS):
        t0 = time()
        total_neg_log_likelihood = 0
        total_num_output_samples = 0
        iteration = 0
        for X, Y, P in get_minibatch(data.TRAIN_FILE2, MINIBATCH_SIZE, shuffle=True, with_pauses=True):
            total_neg_log_likelihood += train_model(X, P, Y, learning_rate)
            total_num_output_samples += np.prod(Y.shape)
            iteration += 1
            if iteration % 100 == 0:
                sys.stdout.write("PPL: %.4f; Speed: %.2f sps\n" % (np.exp(total_neg_log_likelihood / total_num_output_samples), total_num_output_samples / max(time() - t0, 1e-100)))
                sys.stdout.flush()
        print "Total number of training labels: %d" % total_num_output_samples

        total_neg_log_likelihood = 0
        total_num_output_samples = 0
        for X, Y, P in get_minibatch(data.DEV_FILE2, MINIBATCH_SIZE, shuffle=False, with_pauses=True):
            total_neg_log_likelihood += validate_model(X, P, Y)
            total_num_output_samples += np.prod(Y.shape)
        print "Total number of validation labels: %d" % total_num_output_samples

        ppl = np.exp(total_neg_log_likelihood / total_num_output_samples)
        validation_ppl_history.append(ppl)

        print "Validation perplexity is %s" % np.round(ppl, 4)

        if ppl <= best_ppl:
            best_ppl = ppl
            net.save(model_file_name, gsums=gsums, learning_rate=learning_rate, validation_ppl_history=validation_ppl_history, best_validation_ppl=best_ppl, epoch=epoch, random_state=rng.get_state())
        elif best_ppl not in validation_ppl_history[-PATIENCE_EPOCHS:]:
            print "Finished!"
            break