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#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
"""
Replabel transforms for use with flashlight's ASG criterion.
"""
def replabel_symbol(i):
"""
Replabel symbols used in flashlight, currently just "1", "2", ...
This prevents training with numeral tokens, so this might change in the future
"""
return str(i)
def pack_replabels(tokens, dictionary, max_reps):
"""
Pack a token sequence so that repeated symbols are replaced by replabels
"""
if len(tokens) == 0 or max_reps <= 0:
return tokens
replabel_value_to_idx = [0] * (max_reps + 1)
for i in range(1, max_reps + 1):
replabel_value_to_idx[i] = dictionary.index(replabel_symbol(i))
result = []
prev_token = -1
num_reps = 0
for token in tokens:
if token == prev_token and num_reps < max_reps:
num_reps += 1
else:
if num_reps > 0:
result.append(replabel_value_to_idx[num_reps])
num_reps = 0
result.append(token)
prev_token = token
if num_reps > 0:
result.append(replabel_value_to_idx[num_reps])
return result
def unpack_replabels(tokens, dictionary, max_reps):
"""
Unpack a token sequence so that replabels are replaced by repeated symbols
"""
if len(tokens) == 0 or max_reps <= 0:
return tokens
replabel_idx_to_value = {}
for i in range(1, max_reps + 1):
replabel_idx_to_value[dictionary.index(replabel_symbol(i))] = i
result = []
prev_token = -1
for token in tokens:
try:
for _ in range(replabel_idx_to_value[token]):
result.append(prev_token)
prev_token = -1
except KeyError:
result.append(token)
prev_token = token
return result