def create_model_using_pretrained_encoder(weights, biases, input_shape, input_var, mask_shape, mask_var,
lstm_size=250, win=T.iscalar('theta'), output_classes=26,
w_init_fn=las.init.Orthogonal(),
use_peepholes=False, nonlinearities=rectify):
gate_parameters = Gate(
W_in=w_init_fn, W_hid=w_init_fn,
b=las.init.Constant(0.))
cell_parameters = Gate(
W_in=w_init_fn, W_hid=w_init_fn,
# Setting W_cell to None denotes that no cell connection will be used.
W_cell=None, b=las.init.Constant(0.),
# By convention, the cell nonlinearity is tanh in an LSTM.
nonlinearity=tanh)
l_in = InputLayer(input_shape, input_var, 'input')
l_mask = InputLayer(mask_shape, mask_var, 'mask')
symbolic_batchsize = l_in.input_var.shape[0]
symbolic_seqlen = l_in.input_var.shape[1]
l_reshape1 = ReshapeLayer(l_in, (-1, input_shape[-1]), name='reshape1')
l_encoder = create_pretrained_encoder(l_reshape1, weights, biases,
[2000, 1000, 500, 50],
[nonlinearities, nonlinearities, nonlinearities, linear],
['fc1', 'fc2', 'fc3', 'bottleneck'])
encoder_len = las.layers.get_output_shape(l_encoder)[-1]
l_reshape2 = ReshapeLayer(l_encoder, (symbolic_batchsize, symbolic_seqlen, encoder_len), name='reshape2')
l_delta = DeltaLayer(l_reshape2, win, name='delta')
l_lstm, l_lstm_back = create_blstm(l_delta, l_mask, lstm_size, cell_parameters, gate_parameters, 'bstm1',
use_peepholes)
# We'll combine the forward and backward layer output by summing.
# Merge layers take in lists of layers to merge as input.
l_sum1 = ElemwiseSumLayer([l_lstm, l_lstm_back], name='sum1')
l_forward_slice1 = SliceLayer(l_sum1, -1, 1, name='slice1')
# Now, we can apply feed-forward layers as usual.
# We want the network to predict a classification for the sequence,
# so we'll use a the number of classes.
l_out = DenseLayer(
l_forward_slice1, num_units=output_classes, nonlinearity=las.nonlinearities.softmax, name='output')
return l_out
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