#!/usr/bin/env python
# Tsung-Yi Lin <tl483@cornell.edu>
# Ramakrishna Vedantam <vrama91@vt.edu>
import copy
from collections import defaultdict
import numpy as np
import pdb
import math
import pickle
import os
def precook(s, n=4, out=False):
"""
Takes a string as input and returns an object that can be given to
either cook_refs or cook_test. This is optional: cook_refs and cook_test
can take string arguments as well.
:param s: string : sentence to be converted into ngrams
:param n: int : number of ngrams for which representation is calculated
:return: term frequency vector for occuring ngrams
"""
words = s.split()
counts = defaultdict(int)
for k in range(1,n+1):
for i in range(len(words)-k+1):
ngram = tuple(words[i:i+k])
counts[ngram] += 1
return counts
def cook_refs(refs, n=4): ## lhuang: oracle will call with "average"
'''Takes a list of reference sentences for a single segment
and returns an object that encapsulates everything that BLEU
needs to know about them.
:param refs: list of string : reference sentences for some image
:param n: int : number of ngrams for which (ngram) representation is calculated
:return: result (list of dict)
'''
return [precook(ref, n) for ref in refs]
def cook_test(test, n=4):
'''Takes a test sentence and returns an object that
encapsulates everything that BLEU needs to know about it.
:param test: list of string : hypothesis sentence for some image
:param n: int : number of ngrams for which (ngram) representation is calculated
:return: result (dict)
'''
return precook(test, n, True)
class CiderScorer(object):
"""CIDEr scorer.
"""
def copy(self):
''' copy the refs.'''
new = CiderScorer(n=self.n)
new.ctest = copy.copy(self.ctest)
new.crefs = copy.copy(self.crefs)
return new
def __init__(self, df_mode="corpus", test=None, refs=None, n=4, sigma=6.0):
''' singular instance '''
self.n = n
self.sigma = sigma
self.crefs = []
self.ctest = []
self.df_mode = df_mode
self.ref_len = None
if self.df_mode != "corpus":
pkl_file = pickle.load(open(os.path.join('data', df_mode + '.p'),'rb'))
self.ref_len = pkl_file['ref_len']
self.document_frequency = pkl_file['document_frequency']
self.cook_append(test, refs)
def clear(self):
self.crefs = []
self.ctest = []
def cook_append(self, test, refs):
'''called by constructor and __iadd__ to avoid creating new instances.'''
if refs is not None:
self.crefs.append(cook_refs(refs))
if test is not None:
self.ctest.append(cook_test(test)) ## N.B.: -1
else:
self.ctest.append(None) # lens of crefs and ctest have to match
def size(self):
assert len(self.crefs) == len(self.ctest), "refs/test mismatch! %d<>%d" % (len(self.crefs), len(self.ctest))
return len(self.crefs)
def __iadd__(self, other):
'''add an instance (e.g., from another sentence).'''
if type(other) is tuple:
## avoid creating new CiderScorer instances
self.cook_append(other[0], other[1])
else:
self.ctest.extend(other.ctest)
self.crefs.extend(other.crefs)
return self
def compute_doc_freq(self):
'''
Compute term frequency for reference data.
This will be used to compute idf (inverse document frequency later)
The term frequency is stored in the object
:return: None
'''
for refs in self.crefs:
# refs, k ref captions of one image
for ngram in set([ngram for ref in refs for (ngram,count) in ref.items()]):
self.document_frequency[ngram] += 1
# maxcounts[ngram] = max(maxcounts.get(ngram,0), count)
def compute_cider(self):
def counts2vec(cnts):
"""
Function maps counts of ngram to vector of tfidf weights.
The function returns vec, an array of dictionary that store mapping of n-gram and tf-idf weights.
The n-th entry of array denotes length of n-grams.
:param cnts:
:return: vec (array of dict), norm (array of float), length (int)
"""
vec = [defaultdict(float) for _ in range(self.n)]
length = 0
norm = [0.0 for _ in range(self.n)]
for (ngram,term_freq) in cnts.items():
# give word count 1 if it doesn't appear in reference corpus
df = np.log(max(1.0, self.document_frequency[ngram]))
# ngram index
n = len(ngram)-1
# tf (term_freq) * idf (precomputed idf) for n-grams
vec[n][ngram] = float(term_freq)*(self.ref_len - df)
# compute norm for the vector. the norm will be used for computing similarity
norm[n] += pow(vec[n][ngram], 2)
if n == 1:
length += term_freq
norm = [np.sqrt(n) for n in norm]
return vec, norm, length
def sim(vec_hyp, vec_ref, norm_hyp, norm_ref, length_hyp, length_ref):
'''
Compute the cosine similarity of two vectors.
:param vec_hyp: array of dictionary for vector corresponding to hypothesis
:param vec_ref: array of dictionary for vector corresponding to reference
:param norm_hyp: array of float for vector corresponding to hypothesis
:param norm_ref: array of float for vector corresponding to reference
:param length_hyp: int containing length of hypothesis
:param length_ref: int containing length of reference
:return: array of score for each n-grams cosine similarity
'''
delta = float(length_hyp - length_ref)
# measure consine similarity
val = np.array([0.0 for _ in range(self.n)])
for n in range(self.n):
# ngram
for (ngram,count) in vec_hyp[n].items():
# vrama91 : added clipping
val[n] += min(vec_hyp[n][ngram], vec_ref[n][ngram]) * vec_ref[n][ngram]
if (norm_hyp[n] != 0) and (norm_ref[n] != 0):
val[n] /= (norm_hyp[n]*norm_ref[n])
assert(not math.isnan(val[n]))
# vrama91: added a length based gaussian penalty
val[n] *= np.e**(-(delta**2)/(2*self.sigma**2))
return val
# compute log reference length
if self.df_mode == "corpus":
self.ref_len = np.log(float(len(self.crefs)))
#elif self.df_mode == "coco-val":
# if coco option selected, use length of coco-val set
# self.ref_len = np.log(float(40504))
scores = []
for test, refs in zip(self.ctest, self.crefs):
# compute vector for test captions
vec, norm, length = counts2vec(test)
# compute vector for ref captions
score = np.array([0.0 for _ in range(self.n)])
for ref in refs:
vec_ref, norm_ref, length_ref = counts2vec(ref)
score += sim(vec, vec_ref, norm, norm_ref, length, length_ref)
# change by vrama91 - mean of ngram scores, instead of sum
score_avg = np.mean(score)
# divide by number of references
score_avg /= len(refs)
# multiply score by 10
score_avg *= 10.0
# append score of an image to the score list
scores.append(score_avg)
return scores
def compute_score(self, option=None, verbose=0):
# compute idf
if self.df_mode == "corpus":
self.document_frequency = defaultdict(float)
self.compute_doc_freq()
# assert to check document frequency
assert(len(self.ctest) >= max(self.document_frequency.values()))
# import json for now and write the corresponding files
# compute cider score
score = self.compute_cider()
# debug
# print score
return np.mean(np.array(score)), np.array(score)
