detectability.py

# Import necessary libraries
import nltk
import numpy as np
import torch
import matplotlib.pyplot as plt
from sklearn.metrics.pairwise import cosine_similarity
from transformers import BertModel, BertTokenizer
from sentence_transformers import SentenceTransformer
from nltk.translate.bleu_score import sentence_bleu, SmoothingFunction

# Download NLTK data if not already present
nltk.download('punkt', quiet=True)

class SentenceDetectabilityCalculator:
    """
    A class to calculate and analyze detectability metrics between an original sentence and paraphrased sentences.
    """

    def __init__(self, original_sentence, paraphrased_sentences):
        """
        Initialize the calculator with the original sentence and a list of paraphrased sentences.
        """
        self.original_sentence = original_sentence
        self.paraphrased_sentences = paraphrased_sentences
        self.metrics = {
            'BLEU Score': {},
            'Cosine Similarity': {},
            'STS Score': {}
        }
        self.normalized_metrics = {
            'BLEU Score': {},
            'Cosine Similarity': {},
            'STS Score': {}
        }
        self.combined_detectabilities = {}

        # Load pre-trained models
        self.bert_model = BertModel.from_pretrained('bert-base-uncased')
        self.bert_tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
        self.sts_model = SentenceTransformer('paraphrase-MiniLM-L6-v2')
        
        # Calculate original embeddings
        self.original_embedding = self._get_sentence_embedding(self.original_sentence)
        self.sts_original_embedding = self.sts_model.encode(self.original_sentence)

    def calculate_all_metrics(self):
        """
        Calculate all detectability metrics for each paraphrased sentence.
        """
        for idx, paraphrased_sentence in enumerate(self.paraphrased_sentences):
            key = f"Sentence_{idx + 1}"
            self.metrics['BLEU Score'][key] = self._calculate_bleu(self.original_sentence, paraphrased_sentence)
            paraphrase_embedding = self._get_sentence_embedding(paraphrased_sentence)
            self.metrics['Cosine Similarity'][key] = cosine_similarity([self.original_embedding], [paraphrase_embedding])[0][0]
            sts_paraphrase_embedding = self.sts_model.encode(paraphrased_sentence)
            self.metrics['STS Score'][key] = cosine_similarity([self.sts_original_embedding], [sts_paraphrase_embedding])[0][0]

    def normalize_metrics(self):
        """
        Normalize all metrics to be between 0 and 1.
        """
        for metric_name, metric_dict in self.metrics.items():
            self.normalized_metrics[metric_name] = self._normalize_dict(metric_dict)

    def calculate_combined_detectability(self):
        """
        Calculate the combined detectability using the root mean square of the normalized metrics.
        """
        for key in self.normalized_metrics['BLEU Score'].keys():
            rms = np.sqrt(sum(
                self.normalized_metrics[metric][key] ** 2 for metric in self.normalized_metrics
            ) / len(self.normalized_metrics))
            self.combined_detectabilities[key] = rms

    def plot_metrics(self):
        """
        Plot each normalized metric and the combined detectability in separate graphs.
        """
        keys = list(self.normalized_metrics['BLEU Score'].keys())
        indices = np.arange(len(keys))

        # Prepare data for plotting
        metrics = {name: [self.normalized_metrics[name][key] for key in keys] for name in self.normalized_metrics}

        # Plot each metric separately
        for metric_name, values in metrics.items():
            plt.figure(figsize=(12, 6))
            plt.plot(indices, values, marker='o', color=np.random.rand(3,))
            plt.xlabel('Sentence Index')
            plt.ylabel('Normalized Value (0-1)')
            plt.title(f'Normalized {metric_name}')
            plt.grid(True)
            plt.tight_layout()
            plt.show()

    # Private methods for metric calculations
    def _calculate_bleu(self, reference, candidate):
        """
        Calculate the BLEU score between the original and paraphrased sentence using smoothing.
        """
        reference_tokens = nltk.word_tokenize(reference)
        candidate_tokens = nltk.word_tokenize(candidate)
        smoothing = SmoothingFunction().method1
        return sentence_bleu([reference_tokens], candidate_tokens, smoothing_function=smoothing)

    def _get_sentence_embedding(self, sentence):
        """
        Get sentence embedding using BERT.
        """
        tokens = self.bert_tokenizer(sentence, return_tensors='pt', padding=True, truncation=True, max_length=512)
        with torch.no_grad():
            outputs = self.bert_model(**tokens)
        return outputs.last_hidden_state.mean(dim=1).squeeze().numpy()

    def _normalize_dict(self, metric_dict):
        """
        Normalize the values in a dictionary to be between 0 and 1.
        """
        values = np.array(list(metric_dict.values()))
        min_val = values.min()
        max_val = values.max()
        # Avoid division by zero if all values are the same
        return dict(zip(metric_dict.keys(), np.zeros_like(values) if max_val - min_val == 0 else (values - min_val) / (max_val - min_val)))

    # Getter methods
    def get_normalized_metrics(self):
        """
        Get all normalized metrics as a dictionary.
        """
        return self.normalized_metrics

    def get_combined_detectabilities(self):
        """
        Get the dictionary of combined detectability values.
        """
        return self.combined_detectabilities


# Example usage
if __name__ == "__main__":
    # Original sentence
    original_sentence = "The quick brown fox jumps over the lazy dog"

    # Paraphrased sentences
    paraphrased_sentences = [
    # Original 1: "A swift auburn fox leaps across a sleepy canine."
    "The swift auburn fox leaps across a sleepy canine.",
    "A quick auburn fox leaps across a sleepy canine.",
    "A swift ginger fox leaps across a sleepy canine.",
    "A swift auburn fox bounds across a sleepy canine.",
    "A swift auburn fox leaps across a tired canine.",
    "Three swift auburn foxes leap across a sleepy canine.",
    "The vulpine specimen rapidly traverses over a dormant dog.",
    "Like lightning, the russet hunter soars over the drowsy guardian.",
    "Tha quick ginger fox jumps o'er the lazy hound, ye ken.",
    "One rapid Vulpes vulpes traverses the path of a quiescent canine.",
    "A swift auburn predator navigates across a lethargic pet.",
    "Subject A (fox) demonstrates velocity over Subject B (dog).",

    # Original 2: "The agile russet fox bounds over an idle hound."
    "Some agile russet foxes bound over an idle hound.",
    "The nimble russet fox bounds over an idle hound.",
    "The agile brown fox bounds over an idle hound.",
    "The agile russet fox jumps over an idle hound.",
    "The agile russet fox bounds over a lazy hound.",
    "Two agile russet foxes bound over an idle hound.",
    "A dexterous vulpine surpasses a stationary canine.",
    "Quick as thought, the copper warrior sails over the guardian.",
    "Tha nimble reddish fox jumps o'er the doggo, don't ya know.",
    "A dexterous V. vulpes exceeds the plane of an inactive canine.",
    "An agile russet hunter maneuvers above a resting hound.",
    "Test subject F-1 achieves displacement superior to subject D-1.",

    # Original 3: "A nimble mahogany vulpine vaults above a drowsy dog."
    "The nimble mahogany vulpine vaults above a drowsy dog.",
    "A swift mahogany vulpine vaults above a drowsy dog.",
    "A nimble reddish vulpine vaults above a drowsy dog.",
    "A nimble mahogany fox vaults above a drowsy dog.",
    "A nimble mahogany vulpine leaps above a drowsy dog.",
    "Four nimble mahogany vulpines vault above a drowsy dog.",
    "An agile specimen of reddish fur surpasses a somnolent canine.",
    "Fleet as wind, the earth-toned hunter soars over the sleepy guard.",
    "Tha quick brown beastie jumps o'er the tired pup, aye.",
    "Single V. vulpes demonstrates vertical traverse over C. familiaris.",
    "A nimble rust-colored predator crosses above a drowsy pet.",
    "Observed: Subject Red executes vertical motion over Subject Gray.",

    # Original 4: "The speedy copper-colored fox hops over the lethargic pup."
    "A speedy copper-colored fox hops over the lethargic pup.",
    "The quick copper-colored fox hops over the lethargic pup.",
    "The speedy bronze fox hops over the lethargic pup.",
    "The speedy copper-colored fox jumps over the lethargic pup.",
    "The speedy copper-colored fox hops over the tired pup.",
    "Multiple speedy copper-colored foxes hop over the lethargic pup.",
    "A rapid vulpine of bronze hue traverses an inactive young canine.",
    "Swift as a dart, the metallic hunter bounds over the lazy puppy.",
    "Tha fast copper beastie leaps o'er the sleepy wee dog.",
    "1 rapid V. vulpes crosses above 1 juvenile C. familiaris.",
    "A fleet copper-toned predator moves past a sluggish young dog.",
    "Field note: Adult fox subject exceeds puppy subject vertically.",

    # Original 5: "A rapid tawny fox springs over a sluggish dog."
    "The rapid tawny fox springs over a sluggish dog.",
    "A quick tawny fox springs over a sluggish dog.",
    "A rapid golden fox springs over a sluggish dog.",
    "A rapid tawny fox jumps over a sluggish dog.",
    "A rapid tawny fox springs over a lazy dog.",
    "Six rapid tawny foxes spring over a sluggish dog.",
    "An expeditious yellowish vulpine surpasses a torpid canine.",
    "Fast as a bullet, the golden hunter vaults over the idle guard.",
    "Tha swift yellowy fox jumps o'er the lazy mutt, aye.",
    "One V. vulpes displays rapid transit over one inactive C. familiaris.",
    "A speedy yellow-brown predator bypasses a motionless dog.",
    "Log entry: Vulpine subject achieves swift vertical displacement.",

    # Original 6: "The fleet-footed chestnut fox soars above an indolent canine."
    "A fleet-footed chestnut fox soars above an indolent canine.",
    "The swift chestnut fox soars above an indolent canine.",
    "The fleet-footed brown fox soars above an indolent canine.",
    "The fleet-footed chestnut fox leaps above an indolent canine.",
    "The fleet-footed chestnut fox soars above a lazy canine.",
    "Several fleet-footed chestnut foxes soar above an indolent canine.",
    "A rapid brown vulpine specimen traverses a lethargic domestic dog.",
    "Graceful as a bird, the nutbrown hunter flies over the lazy guard.",
    "Tha quick brown beastie sails o'er the sleepy hound, ken.",
    "Single agile V. vulpes achieves elevation above stationary canine.",
    "A nimble brown predator glides over an unmoving domestic animal.",
    "Research note: Brown subject displays superior vertical mobility.",

    # Original 7: "A fast ginger fox hurdles past a slothful dog."
    "The fast ginger fox hurdles past a slothful dog.",
    "A quick ginger fox hurdles past a slothful dog.",
    "A fast red fox hurdles past a slothful dog.",
    "A fast ginger fox jumps past a slothful dog.",
    "A fast ginger fox hurdles past a lazy dog.",
    "Five fast ginger foxes hurdle past a slothful dog.",
    "A rapid orange vulpine bypasses a lethargic canine.",
    "Quick as lightning, the flame-colored hunter races past the lazy guard.",
    "Tha swift ginger beastie leaps past the tired doggy, ye see.",
    "1 rapid orange V. vulpes surpasses 1 inactive C. familiaris.",
    "A speedy red-orange predator overtakes a motionless dog.",
    "Data point: Orange subject demonstrates rapid transit past Gray subject.",

    # Original 8: "The spry rusty-colored fox jumps across a dozing hound."
    "A spry rusty-colored fox jumps across a dozing hound.",
    "The agile rusty-colored fox jumps across a dozing hound.",
    "The spry reddish fox jumps across a dozing hound.",
    "The spry rusty-colored fox leaps across a dozing hound.",
    "The spry rusty-colored fox jumps across a sleeping hound.",
    "Multiple spry rusty-colored foxes jump across a dozing hound.",
    "An agile rust-toned vulpine traverses a somnolent canine.",
    "Nimble as thought, the copper hunter bounds over the resting guard.",
    "Tha lively rust-colored beastie hops o'er the snoozin' hound.",
    "Single dexterous V. vulpes crosses path of dormant C. familiaris.",
    "A lithe rust-tinted predator moves past a slumbering dog.",
    "Observation: Russet subject exhibits agility over dormant subject.",

    # Original 9: "A quick tan fox leaps over an inactive dog."
    "The quick tan fox leaps over an inactive dog.",
    "A swift tan fox leaps over an inactive dog.",
    "A quick beige fox leaps over an inactive dog.",
    "A quick tan fox jumps over an inactive dog.",
    "A quick tan fox leaps over a motionless dog.",
    "Seven quick tan foxes leap over an inactive dog.",
    "A rapid light-brown vulpine surpasses a stationary canine.",
    "Fast as wind, the sand-colored hunter soars over the still guard.",
    "Tha nimble tan beastie jumps o'er the quiet doggy, aye.",
    "One agile fawn V. vulpes traverses one immobile C. familiaris.",
    "A fleet tan-colored predator bypasses an unmoving dog.",
    "Field report: Tan subject demonstrates movement over static subject.",

    # Original 10: "The brisk auburn vulpine bounces over a listless canine."
    "Some brisk auburn vulpines bounce over a listless canine.",
    "The quick auburn vulpine bounces over a listless canine.",
    "The brisk russet vulpine bounces over a listless canine.",
    "The brisk auburn fox bounces over a listless canine.",
    "The brisk auburn vulpine jumps over a listless canine.",
    "Five brisk auburn vulpines bounce over a listless canine.",
    "The expeditious specimen supersedes a quiescent Canis lupus.",
    "Swift as wind, the russet hunter vaults over the idle guardian.",
    "Tha quick ginger beastie hops o'er the lazy mutt, aye.",
    "One V. vulpes achieves displacement over inactive C. familiaris.",
    "A high-velocity auburn predator traverses an immobile animal.",
    "Final observation: Red subject shows mobility over Gray subject."
    ]

    # Create the calculator instance
    calculator = SentenceDetectabilityCalculator(original_sentence, paraphrased_sentences)
    
    # Calculate metrics
    calculator.calculate_all_metrics()
    calculator.normalize_metrics()
    calculator.calculate_combined_detectability()
    
    # Plot metrics
    calculator.plot_metrics()

    # Get results
    normalized_metrics = calculator.get_normalized_metrics()
    combined_detectabilities = calculator.get_combined_detectabilities()
    
    print("Normalized Metrics:", normalized_metrics)
    print("Combined Detectabilities:", combined_detectabilities)