# Source code for nlp_architect.models.gnmt.scripts.rouge

```
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# Copyright 2017-2018 Intel Corporation
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# Changes Made from original:
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# pylint: skip-file
"""ROUGE metric implementation.
Copy from tf_seq2seq/seq2seq/metrics/rouge.py.
This is a modified and slightly extended verison of
https://github.com/miso-belica/sumy/blob/dev/sumy/evaluation/rouge.py.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
import itertools
import numpy as np
def _get_ngrams(n, text):
"""Calcualtes n-grams.
Args:
n: which n-grams to calculate
text: An array of tokens
Returns:
A set of n-grams
"""
ngram_set = set()
text_length = len(text)
max_index_ngram_start = text_length - n
for i in range(max_index_ngram_start + 1):
ngram_set.add(tuple(text[i:i + n]))
return ngram_set
def _split_into_words(sentences):
"""Splits multiple sentences into words and flattens the result"""
return list(itertools.chain(*[_.split(" ") for _ in sentences]))
def _get_word_ngrams(n, sentences):
"""Calculates word n-grams for multiple sentences.
"""
assert len(sentences) > 0
assert n > 0
words = _split_into_words(sentences)
return _get_ngrams(n, words)
def _len_lcs(x, y):
"""
Returns the length of the Longest Common Subsequence between sequences x
and y.
Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence
Args:
x: sequence of words
y: sequence of words
Returns
integer: Length of LCS between x and y
"""
table = _lcs(x, y)
n, m = len(x), len(y)
return table[n, m]
def _lcs(x, y):
"""
Computes the length of the longest common subsequence (lcs) between two
strings. The implementation below uses a DP programming algorithm and runs
in O(nm) time where n = len(x) and m = len(y).
Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence
Args:
x: collection of words
y: collection of words
Returns:
Table of dictionary of coord and len lcs
"""
n, m = len(x), len(y)
table = dict()
for i in range(n + 1):
for j in range(m + 1):
if i == 0 or j == 0:
table[i, j] = 0
elif x[i - 1] == y[j - 1]:
table[i, j] = table[i - 1, j - 1] + 1
else:
table[i, j] = max(table[i - 1, j], table[i, j - 1])
return table
def _recon_lcs(x, y):
"""
Returns the Longest Subsequence between x and y.
Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence
Args:
x: sequence of words
y: sequence of words
Returns:
sequence: LCS of x and y
"""
i, j = len(x), len(y)
table = _lcs(x, y)
def _recon(i, j):
"""private recon calculation"""
if i == 0 or j == 0:
return []
elif x[i - 1] == y[j - 1]:
return _recon(i - 1, j - 1) + [(x[i - 1], i)]
elif table[i - 1, j] > table[i, j - 1]:
return _recon(i - 1, j)
else:
return _recon(i, j - 1)
recon_tuple = tuple(map(lambda x: x[0], _recon(i, j)))
return recon_tuple
[docs]def rouge_n(evaluated_sentences, reference_sentences, n=2):
"""
Computes ROUGE-N of two text collections of sentences.
Sourece: http://research.microsoft.com/en-us/um/people/cyl/download/
papers/rouge-working-note-v1.3.1.pdf
Args:
evaluated_sentences: The sentences that have been picked by the summarizer
reference_sentences: The sentences from the referene set
n: Size of ngram. Defaults to 2.
Returns:
A tuple (f1, precision, recall) for ROUGE-N
Raises:
ValueError: raises exception if a param has len <= 0
"""
if len(evaluated_sentences) <= 0 or len(reference_sentences) <= 0:
raise ValueError("Collections must contain at least 1 sentence.")
evaluated_ngrams = _get_word_ngrams(n, evaluated_sentences)
reference_ngrams = _get_word_ngrams(n, reference_sentences)
reference_count = len(reference_ngrams)
evaluated_count = len(evaluated_ngrams)
# Gets the overlapping ngrams between evaluated and reference
overlapping_ngrams = evaluated_ngrams.intersection(reference_ngrams)
overlapping_count = len(overlapping_ngrams)
# Handle edge case. This isn't mathematically correct, but it's good enough
if evaluated_count == 0:
precision = 0.0
else:
precision = overlapping_count / evaluated_count
if reference_count == 0:
recall = 0.0
else:
recall = overlapping_count / reference_count
f1_score = 2.0 * ((precision * recall) / (precision + recall + 1e-8))
# return overlapping_count / reference_count
return f1_score, precision, recall
def _f_p_r_lcs(llcs, m, n):
"""
Computes the LCS-based F-measure score
Source: http://research.microsoft.com/en-us/um/people/cyl/download/papers/
rouge-working-note-v1.3.1.pdf
Args:
llcs: Length of LCS
m: number of words in reference summary
n: number of words in candidate summary
Returns:
Float. LCS-based F-measure score
"""
r_lcs = llcs / m
p_lcs = llcs / n
beta = p_lcs / (r_lcs + 1e-12)
num = (1 + (beta ** 2)) * r_lcs * p_lcs
denom = r_lcs + ((beta ** 2) * p_lcs)
f_lcs = num / (denom + 1e-12)
return f_lcs, p_lcs, r_lcs
[docs]def rouge_l_sentence_level(evaluated_sentences, reference_sentences):
"""
Computes ROUGE-L (sentence level) of two text collections of sentences.
http://research.microsoft.com/en-us/um/people/cyl/download/papers/
rouge-working-note-v1.3.1.pdf
Calculated according to:
R_lcs = LCS(X,Y)/m
P_lcs = LCS(X,Y)/n
F_lcs = ((1 + beta^2)*R_lcs*P_lcs) / (R_lcs + (beta^2) * P_lcs)
where:
X = reference summary
Y = Candidate summary
m = length of reference summary
n = length of candidate summary
Args:
evaluated_sentences: The sentences that have been picked by the summarizer
reference_sentences: The sentences from the referene set
Returns:
A float: F_lcs
Raises:
ValueError: raises exception if a param has len <= 0
"""
if len(evaluated_sentences) <= 0 or len(reference_sentences) <= 0:
raise ValueError("Collections must contain at least 1 sentence.")
reference_words = _split_into_words(reference_sentences)
evaluated_words = _split_into_words(evaluated_sentences)
m = len(reference_words)
n = len(evaluated_words)
lcs = _len_lcs(evaluated_words, reference_words)
return _f_p_r_lcs(lcs, m, n)
def _union_lcs(evaluated_sentences, reference_sentence):
"""
Returns LCS_u(r_i, C) which is the LCS score of the union longest common
subsequence between reference sentence ri and candidate summary C. For example
if r_i= w1 w2 w3 w4 w5, and C contains two sentences: c1 = w1 w2 w6 w7 w8 and
c2 = w1 w3 w8 w9 w5, then the longest common subsequence of r_i and c1 is
"w1 w2" and the longest common subsequence of r_i and c2 is "w1 w3 w5". The
union longest common subsequence of r_i, c1, and c2 is "w1 w2 w3 w5" and
LCS_u(r_i, C) = 4/5.
Args:
evaluated_sentences: The sentences that have been picked by the summarizer
reference_sentence: One of the sentences in the reference summaries
Returns:
float: LCS_u(r_i, C)
ValueError:
Raises exception if a param has len <= 0
"""
if len(evaluated_sentences) <= 0:
raise ValueError("Collections must contain at least 1 sentence.")
lcs_union = set()
reference_words = _split_into_words([reference_sentence])
combined_lcs_length = 0
for eval_s in evaluated_sentences:
evaluated_words = _split_into_words([eval_s])
lcs = set(_recon_lcs(reference_words, evaluated_words))
combined_lcs_length += len(lcs)
lcs_union = lcs_union.union(lcs)
union_lcs_count = len(lcs_union)
union_lcs_value = union_lcs_count / combined_lcs_length
return union_lcs_value
[docs]def rouge_l_summary_level(evaluated_sentences, reference_sentences):
"""
Computes ROUGE-L (summary level) of two text collections of sentences.
http://research.microsoft.com/en-us/um/people/cyl/download/papers/
rouge-working-note-v1.3.1.pdf
Calculated according to:
R_lcs = SUM(1, u)[LCS<union>(r_i,C)]/m
P_lcs = SUM(1, u)[LCS<union>(r_i,C)]/n
F_lcs = ((1 + beta^2)*R_lcs*P_lcs) / (R_lcs + (beta^2) * P_lcs)
where:
SUM(i,u) = SUM from i through u
u = number of sentences in reference summary
C = Candidate summary made up of v sentences
m = number of words in reference summary
n = number of words in candidate summary
Args:
evaluated_sentences: The sentences that have been picked by the summarizer
reference_sentence: One of the sentences in the reference summaries
Returns:
A float: F_lcs
Raises:
ValueError: raises exception if a param has len <= 0
"""
if len(evaluated_sentences) <= 0 or len(reference_sentences) <= 0:
raise ValueError("Collections must contain at least 1 sentence.")
# total number of words in reference sentences
m = len(_split_into_words(reference_sentences))
# total number of words in evaluated sentences
n = len(_split_into_words(evaluated_sentences))
union_lcs_sum_across_all_references = 0
for ref_s in reference_sentences:
union_lcs_sum_across_all_references += _union_lcs(evaluated_sentences,
ref_s)
return _f_p_r_lcs(union_lcs_sum_across_all_references, m, n)
[docs]def rouge(hypotheses, references):
"""Calculates average rouge scores for a list of hypotheses and
references"""
# Filter out hyps that are of 0 length
# hyps_and_refs = zip(hypotheses, references)
# hyps_and_refs = [_ for _ in hyps_and_refs if len(_[0]) > 0]
# hypotheses, references = zip(*hyps_and_refs)
# Calculate ROUGE-1 F1, precision, recall scores
rouge_1 = [rouge_n([hyp], [ref], 1) for hyp, ref in zip(hypotheses, references)]
rouge_1_f, rouge_1_p, rouge_1_r = map(np.mean, zip(*rouge_1))
# Calculate ROUGE-2 F1, precision, recall scores
rouge_2 = [rouge_n([hyp], [ref], 2) for hyp, ref in zip(hypotheses, references)]
rouge_2_f, rouge_2_p, rouge_2_r = map(np.mean, zip(*rouge_2))
# Calculate ROUGE-L F1, precision, recall scores
rouge_l = [rouge_l_sentence_level([hyp], [ref]) for hyp, ref in zip(hypotheses, references)]
rouge_l_f, rouge_l_p, rouge_l_r = map(np.mean, zip(*rouge_l))
return {
"rouge_1/f_score": rouge_1_f,
"rouge_1/r_score": rouge_1_r,
"rouge_1/p_score": rouge_1_p,
"rouge_2/f_score": rouge_2_f,
"rouge_2/r_score": rouge_2_r,
"rouge_2/p_score": rouge_2_p,
"rouge_l/f_score": rouge_l_f,
"rouge_l/r_score": rouge_l_r,
"rouge_l/p_score": rouge_l_p,
}
```