def sample_sequence(*, hparams, length, start_token=None, batch_size=None, context=None, temperature=1, top_k=0, top_p=0.0):
if start_token is None:
assert context is not None, 'Specify exactly one of start_token and context!'
else:
assert context is None, 'Specify exactly one of start_token and context!'
context = tf.fill([batch_size, 1], start_token)
def step(hparams, tokens, past=None):
lm_output = model.model(hparams=hparams, X=tokens, past=past, reuse=tf.AUTO_REUSE)
logits = lm_output['logits'][:, :, :hparams.n_vocab]
presents = lm_output['present']
presents.set_shape(model.past_shape(hparams=hparams, batch_size=batch_size))
return {
'logits': logits,
'presents': presents,
}
with tf.name_scope('sample_sequence'):
# Don't feed the last context token -- leave that to the loop below
# TODO: Would be slightly faster if we called step on the entire context,
# rather than leaving the last token transformer calculation to the while loop.
context_output = step(hparams, context[:, :-1])
def body(past, prev, output):
next_outputs = step(hparams, prev[:, tf.newaxis], past=past)
logits = next_outputs['logits'][:, -1, :] / tf.to_float(temperature)
if top_p > 0.0:
logits = top_p_logits(logits, p=top_p)
else:
logits = top_k_logits(logits, k=top_k)
samples = tf.multinomial(logits, num_samples=1, output_dtype=tf.int32)
return [
tf.concat([past, next_outputs['presents']], axis=-2),
tf.squeeze(samples, axis=[1]),
tf.concat([output, samples], axis=1),
]
def cond(*args):
return True
_, _, tokens = tf.while_loop(
cond=cond, body=body,
maximum_iterations=length,
loop_vars=[
context_output['presents'],
context[:, -1],
context,
],
shape_invariants=[
tf.TensorShape(model.past_shape(hparams=hparams, batch_size=batch_size)),
tf.TensorShape([batch_size]),
tf.TensorShape([batch_size, None]),
],
back_prop=False,
)
return tokens
def step(hparams, tokens, past=None):
lm_output = model.model(hparams=hparams, X=tokens, past=past, reuse=tf.AUTO_REUSE)
logits = lm_output['logits'][:, :, :hparams.n_vocab]
presents = lm_output['present']
presents.set_shape(model.past_shape(hparams=hparams, batch_size=batch_size))
return {
'logits': logits,
'presents': presents,
}
def sample_sequence(*,
hparams,
length,
start_token=None,
batch_size=None,
context=None,
temperature=1,
top_k=0,
top_p=1):
if start_token is None:
assert context is not None, 'Specify exactly one of start_token and context!'
else:
assert context is None, 'Specify exactly one of start_token and context!'
context = tf.fill([batch_size, 1], start_token)
def step(hparams, tokens, past=None):
lm_output = model.model(hparams=hparams,
X=tokens,
past=past,
reuse=tf.AUTO_REUSE)
logits = lm_output['logits'][:, :, :hparams.n_vocab]
presents = lm_output['present']
presents.set_shape(
model.past_shape(hparams=hparams, batch_size=batch_size))
return {
'logits': logits,
'presents': presents,
}
with tf.name_scope('sample_sequence'):
def body(past, prev, output):
next_outputs = step(hparams, prev, past=past)
logits = next_outputs['logits'][:,
-1, :] / tf.to_float(temperature)
logits = top_k_logits(logits, k=top_k)
logits = top_p_logits(logits, p=top_p)
samples = tf.multinomial(logits,
num_samples=1,
output_dtype=tf.int32)
return [
next_outputs['presents'] if past is None else tf.concat(
[past, next_outputs['presents']], axis=-2), samples,
tf.concat([output, samples], axis=1)
]
past, prev, output = body(None, context, context)
def cond(*args):
return True
_, _, tokens = tf.while_loop(
cond=cond,
body=body,
maximum_iterations=length - 1,
loop_vars=[past, prev, output],
shape_invariants=[
tf.TensorShape(
model.past_shape(hparams=hparams, batch_size=batch_size)),
tf.TensorShape([batch_size, None]),
tf.TensorShape([batch_size, None]),
],
back_prop=False,
)
return tokens
