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import theano
from theano import tensor
import numpy
from blocks.bricks import Tanh, Softmax, Linear, MLP, Identity, Rectifier
from blocks.bricks.lookup import LookupTable
from blocks.bricks.recurrent import LSTM
from blocks.filter import VariableFilter
from blocks.roles import WEIGHT
from blocks.graph import ComputationGraph, apply_dropout, apply_noise
def make_bidir_lstm_stack(seq, seq_dim, mask, sizes, skip=True, name=''):
bricks = []
curr_dim = [seq_dim]
curr_hidden = [seq]
hidden_list = []
for k, dim in enumerate(sizes):
fwd_lstm_ins = [Linear(input_dim=d, output_dim=4*dim, name='%s_fwd_lstm_in_%d_%d'%(name,k,l)) for l, d in enumerate(curr_dim)]
fwd_lstm = LSTM(dim=dim, activation=Tanh(), name='%s_fwd_lstm_%d'%(name,k))
bwd_lstm_ins = [Linear(input_dim=d, output_dim=4*dim, name='%s_bwd_lstm_in_%d_%d'%(name,k,l)) for l, d in enumerate(curr_dim)]
bwd_lstm = LSTM(dim=dim, activation=Tanh(), name='%s_bwd_lstm_%d'%(name,k))
bricks = bricks + [fwd_lstm, bwd_lstm] + fwd_lstm_ins + bwd_lstm_ins
fwd_tmp = sum(x.apply(v) for x, v in zip(fwd_lstm_ins, curr_hidden))
bwd_tmp = sum(x.apply(v) for x, v in zip(bwd_lstm_ins, curr_hidden))
fwd_hidden, _ = fwd_lstm.apply(fwd_tmp, mask=mask)
bwd_hidden, _ = bwd_lstm.apply(bwd_tmp[::-1], mask=mask[::-1])
hidden_list = hidden_list + [fwd_hidden, bwd_hidden]
if skip:
curr_hidden = [seq, fwd_hidden, bwd_hidden[::-1]]
curr_dim = [seq_dim, dim, dim]
else:
curr_hidden = [fwd_hidden, bwd_hidden[::-1]]
curr_dim = [dim, dim]
return bricks, hidden_list
class Model():
def __init__(self, config, vocab_size):
question = tensor.imatrix('question')
question_mask = tensor.imatrix('question_mask')
context = tensor.imatrix('context')
context_mask = tensor.imatrix('context_mask')
answer = tensor.ivector('answer')
candidates = tensor.imatrix('candidates')
candidates_mask = tensor.imatrix('candidates_mask')
bricks = []
question = question.dimshuffle(1, 0)
question_mask = question_mask.dimshuffle(1, 0)
context = context.dimshuffle(1, 0)
context_mask = context_mask.dimshuffle(1, 0)
# Embed questions and cntext
embed = LookupTable(vocab_size, config.embed_size, name='question_embed')
bricks.append(embed)
qembed = embed.apply(question)
cembed = embed.apply(context)
qlstms, qhidden_list = make_bidir_lstm_stack(qembed, config.embed_size, question_mask.astype(theano.config.floatX),
config.question_lstm_size, config.question_skip_connections, 'q')
clstms, chidden_list = make_bidir_lstm_stack(cembed, config.embed_size, context_mask.astype(theano.config.floatX),
config.ctx_lstm_size, config.ctx_skip_connections, 'ctx')
bricks = bricks + qlstms + clstms
# Calculate question encoding (concatenate layer1)
if config.question_skip_connections:
qenc_dim = 2*sum(config.question_lstm_size)
qenc = tensor.concatenate([h[-1,:,:] for h in qhidden_list], axis=1)
else:
qenc_dim = 2*config.question_lstm_size[-1]
qenc = tensor.concatenate([h[-1,:,:] for h in qhidden_list[-2:]], axis=1)
qenc.name = 'qenc'
# Calculate context encoding (concatenate layer1)
if config.ctx_skip_connections:
cenc_dim = 2*sum(config.ctx_lstm_size)
cenc = tensor.concatenate(chidden_list, axis=2)
else:
cenc_dim = 2*config.ctx_lstm_size[-1]
cenc = tensor.concatenate(chidden_list[-2:], axis=2)
cenc.name = 'cenc'
# Attention mechanism MLP
attention_mlp = MLP(dims=config.attention_mlp_hidden + [1],
activations=config.attention_mlp_activations[1:] + [Identity()],
name='attention_mlp')
attention_qlinear = Linear(input_dim=qenc_dim, output_dim=config.attention_mlp_hidden[0], name='attq')
attention_clinear = Linear(input_dim=cenc_dim, output_dim=config.attention_mlp_hidden[0], use_bias=False, name='attc')
bricks += [attention_mlp, attention_qlinear, attention_clinear]
layer1 = Tanh().apply(attention_clinear.apply(cenc.reshape((cenc.shape[0]*cenc.shape[1], cenc.shape[2])))
.reshape((cenc.shape[0],cenc.shape[1],config.attention_mlp_hidden[0]))
+ attention_qlinear.apply(qenc)[None, :, :])
layer1.name = 'layer1'
att_weights = attention_mlp.apply(layer1.reshape((layer1.shape[0]*layer1.shape[1], layer1.shape[2])))
att_weights.name = 'att_weights_0'
att_weights = att_weights.reshape((layer1.shape[0], layer1.shape[1]))
att_weights.name = 'att_weights'
attended = tensor.sum(cenc * tensor.nnet.softmax(att_weights.T).T[:, :, None], axis=0)
attended.name = 'attended'
# Now we can calculate our output
out_mlp = MLP(dims=[cenc_dim + qenc_dim] + config.out_mlp_hidden + [config.n_entities],
activations=config.out_mlp_activations + [Identity()],
name='out_mlp')
bricks += [out_mlp]
probs = out_mlp.apply(tensor.concatenate([attended, qenc], axis=1))
probs.name = 'probs'
is_candidate = tensor.eq(tensor.arange(config.n_entities, dtype='int32')[None, None, :],
tensor.switch(candidates_mask, candidates, -tensor.ones_like(candidates))[:, :, None]).sum(axis=1)
probs = tensor.switch(is_candidate, probs, -1000 * tensor.ones_like(probs))
# Calculate prediction, cost and error rate
pred = probs.argmax(axis=1)
cost = Softmax().categorical_cross_entropy(answer, probs).mean()
error_rate = tensor.neq(answer, pred).mean()
# Apply dropout
cg = ComputationGraph([cost, error_rate])
if config.w_noise > 0:
noise_vars = VariableFilter(roles=[WEIGHT])(cg)
cg = apply_noise(cg, noise_vars, config.w_noise)
if config.dropout > 0:
cg = apply_dropout(cg, qhidden_list + chidden_list, config.dropout)
[cost_reg, error_rate_reg] = cg.outputs
# Other stuff
cost_reg.name = cost.name = 'cost'
error_rate_reg.name = error_rate.name = 'error_rate'
self.sgd_cost = cost_reg
self.monitor_vars = [[cost_reg], [error_rate_reg]]
self.monitor_vars_valid = [[cost], [error_rate]]
# Initialize bricks
for brick in bricks:
brick.weights_init = config.weights_init
brick.biases_init = config.biases_init
brick.initialize()
# vim: set sts=4 ts=4 sw=4 tw=0 et :
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