bert_inference.py

import os
import sys
import pickle
import torch
import torch.nn.functional as F
import numpy as np
from transformers import AutoTokenizer, AutoModelForSequenceClassification
from sklearn.isotonic import IsotonicRegression
from sklearn.linear_model import LogisticRegression
import warnings
warnings.filterwarnings('ignore')

# Fix numpy compatibility issue
if 'numpy._core' not in sys.modules:
    import numpy.core
    sys.modules['numpy._core'] = numpy.core
    sys.modules['numpy._core._multiarray_umath'] = numpy.core._multiarray_umath

# Configuration
MODEL_NAME = "microsoft/xtremedistil-l6-h256-uncased"
CHECKPOINT_PATH = input("Please enter the path to the BERT model directory: ").strip()
CALIBRATOR_FILE = os.path.join(CHECKPOINT_PATH, "calibrators.pkl")
MAX_LENGTH = 512
BATCH_SIZE = 16
DEVICE = torch.device('cuda' if torch.cuda.is_available() else 'cpu')

# ============================================================================
# CALIBRATION CLASSES (needed for unpickling)
# ============================================================================

class TemperatureScaling:
    def __init__(self):
        self.temperature = 1.0
    def transform(self, logits):
        return logits / self.temperature

class PlattScaling:
    def __init__(self):
        self.calibrator = LogisticRegression()
        self.fitted = False
    def transform(self, logits):
        if not self.fitted:
            raise ValueError("Calibrator not fitted")
        probs = torch.softmax(torch.tensor(logits), dim=-1).numpy()
        scores = probs[:, 1].reshape(-1, 1)
        calibrated_probs = self.calibrator.predict_proba(scores)
        return calibrated_probs

class IsotonicCalibration:
    def __init__(self):
        self.calibrator = IsotonicRegression(out_of_bounds='clip')
        self.fitted = False
    def transform(self, logits):
        if not self.fitted:
            raise ValueError("Calibrator not fitted")
        probs = torch.softmax(torch.tensor(logits), dim=-1).numpy()
        scores = probs[:, 1]
        calibrated_scores = self.calibrator.transform(scores)
        calibrated_probs = np.zeros((len(scores), 2))
        calibrated_probs[:, 1] = calibrated_scores
        calibrated_probs[:, 0] = 1 - calibrated_scores
        return calibrated_probs

class MixNMatchCalibration:
    def __init__(self, n_bins=15, bin_strategy='quantile'):
        self.n_bins = n_bins
        self.bin_strategy = bin_strategy
        self.temperature = 1.0
        self.bin_boundaries = None
        self.bin_calibrators = {}
        self.bin_sample_counts = {}
    
    def _get_bin_mask(self, probs, bin_idx):
        lower = self.bin_boundaries[bin_idx]
        upper = self.bin_boundaries[bin_idx + 1]
        if bin_idx == self.n_bins - 1:
            return (probs >= lower) & (probs <= upper)
        else:
            return (probs >= lower) & (probs < upper)
    
    def transform(self, logits):
        scaled_logits = logits / self.temperature
        probs = torch.softmax(torch.tensor(scaled_logits), dim=-1).numpy()
        class1_probs = probs[:, 1]
        calibrated_probs = np.zeros_like(class1_probs)
        
        for i in range(self.n_bins):
            bin_mask = self._get_bin_mask(class1_probs, i)
            if not np.any(bin_mask):
                continue
            bin_probs = class1_probs[bin_mask]
            if self.bin_calibrators.get(i) is not None:
                cal_type, cal_data = self.bin_calibrators[i]
                if cal_type == 'isotonic':
                    calibrated_bin_probs = cal_data.predict(bin_probs)
                elif cal_type == 'mean':
                    calibrated_bin_probs = bin_probs * cal_data
                calibrated_probs[bin_mask] = np.clip(calibrated_bin_probs, 0, 1)
            else:
                calibrated_probs[bin_mask] = bin_probs
        
        result = np.zeros((len(calibrated_probs), 2))
        result[:, 1] = calibrated_probs
        result[:, 0] = 1 - calibrated_probs
        return result

# ============================================================================
# MODEL LOADING AND PREDICTION
# ============================================================================

def load_model_and_calibrators():
    """Load the model and calibrators"""
    print(f"Loading BERT model from: {CHECKPOINT_PATH}")
    tokenizer = AutoTokenizer.from_pretrained(CHECKPOINT_PATH)
    model = AutoModelForSequenceClassification.from_pretrained(CHECKPOINT_PATH)
    model = model.to(DEVICE)
    model.eval()
    print("BERT model loaded successfully!")
    
    # Load calibrators with compatibility handling
    print(f"Loading calibrators from: {CALIBRATOR_FILE}")
    
    # Add the calibration classes to the current module for unpickling
    import sys
    current_module = sys.modules[__name__]
    
    class CompatibleUnpickler(pickle.Unpickler):
        def find_class(self, module, name):
            # Handle the calibration classes
            if name in ['TemperatureScaling', 'PlattScaling', 'IsotonicCalibration', 'MixNMatchCalibration']:
                return getattr(current_module, name)
            if module == 'numpy._core':
                module = 'numpy.core'
            elif module == 'numpy._core._multiarray_umath':
                module = 'numpy.core._multiarray_umath'
            return super().find_class(module, name)
    
    try:
        with open(CALIBRATOR_FILE, 'rb') as f:
            cal_data = CompatibleUnpickler(f).load()
    except:
        with open(CALIBRATOR_FILE, 'rb') as f:
            cal_data = pickle.load(f)
    
    # Use only mixnmatch calibration
    calibrator = cal_data['calibrators']['mixnmatch']
    
    print("Using calibration: mixnmatch")
    
    return model, tokenizer, calibrator

def predict_batch(model, tokenizer, calibrator, texts):
    """Make predictions on a batch of texts"""
    all_logits = []
    
    model.eval()
    with torch.no_grad():
        for i in range(0, len(texts), BATCH_SIZE):
            batch_texts = texts[i:i + BATCH_SIZE]
            
            encoding = tokenizer(
                batch_texts,
                truncation=True,
                padding=True,
                max_length=MAX_LENGTH,
                return_tensors='pt'
            )
            
            input_ids = encoding['input_ids'].to(DEVICE)
            attention_mask = encoding['attention_mask'].to(DEVICE)
            
            outputs = model(input_ids=input_ids, attention_mask=attention_mask)
            logits = outputs.logits.cpu().numpy()
            all_logits.append(logits)
    
    logits = np.vstack(all_logits)
    
    # Get uncalibrated probabilities
    uncalibrated_probs = torch.softmax(torch.tensor(logits), dim=-1).numpy()
    
    # Apply calibration
    calibrated_output = calibrator.transform(logits)
    if len(calibrated_output.shape) == 1:
        calibrated_probs = np.zeros((len(calibrated_output), 2))
        calibrated_probs[:, 1] = calibrated_output
        calibrated_probs[:, 0] = 1 - calibrated_output
    else:
        calibrated_probs = calibrated_output
    
    # Get predictions and confidence
    predictions = np.argmax(calibrated_probs, axis=1)
    confidence = np.max(calibrated_probs, axis=1)
    
    # Calibration shift
    cal_conf = np.max(calibrated_probs, axis=1)
    uncal_conf = np.max(uncalibrated_probs, axis=1)
    calibration_shift = cal_conf - uncal_conf
    
    return {
        'predictions': predictions,
        'probabilities': calibrated_probs,
        'confidence': confidence,
        'uncalibrated_probs': uncalibrated_probs,
        'calibration_shift': calibration_shift
    }

def process_texts(texts):
    """Process a list of texts and return predictions"""
    model, tokenizer, calibrator = load_model_and_calibrators()
    results = predict_batch(model, tokenizer, calibrator, texts)
    return results

# Example usage
if __name__ == "__main__":
    # Example texts for testing
    sample_texts = [
    # Social Engineering - Manipulative, but flagged wrong
    "URGENT: Your account will be suspended in 2 hours due to suspicious activity. Click this link immediately to verify your identity or lose access forever. -IT Security Team",
    
    # Social Engineering - Non-manipulative
    "Hi, we noticed some unusual login attempts on your account. For your security, please log into your account through our official website when convenient to review your recent activity. If you have concerns, contact our support team at [official number]. -IT Security Team",
    
    # Social Engineering - no context to determine if manipulative
    "Hey! It's Sarah from accounting. I'm working from home and can't access the expense system. Can you quickly send me your login details so I can process your reimbursement today? Thanks!",
    
    # Social Engineering - Non-manipulative  
    "Hi, this is Sarah from accounting. I'm having technical issues with the expense system. Could you please submit your reimbursement request through the official portal, or I can walk you through it when I'm back in the office tomorrow?",
    
    # Emotional Manipulation - Manipulative
    "I guess you don't really care about our friendship since you never make time for me anymore. I've been there for you through everything, but apparently that doesn't matter. Fine, I'll just stop trying.",
    
    # Emotional Manipulation - Non-manipulative
    "I miss spending time together and I'm feeling a bit disconnected lately. I understand you're busy, but I'd love to catch up when you have some free time. Would you be interested in planning something together?",
    
    # Emotional Manipulation - Manipulative
    "You're being way too sensitive about this. You always overreact to everything - I was just joking around. Maybe you should work on not taking things so personally all the time.",
    
    # Emotional Manipulation - Non-manipulative
    "I can see that what I said upset you, and that wasn't my intention. I was trying to be playful, but I can understand how it came across differently. I'm sorry for hurting your feelings."
]
    
    print("Processing sample texts with BERT model...")
    results = process_texts(sample_texts)
    
    for i, text in enumerate(sample_texts):
        print(f"\nText: {text}")
        print(f"Prediction: {results['predictions'][i]}")
        print(f"Confidence: {results['confidence'][i]:.4f}")
        print(f"Probabilities: Class 0: {results['probabilities'][i][0]:.4f}, Class 1: {results['probabilities'][i][1]:.4f}")
        print(f"Calibration Shift: {results['calibration_shift'][i]:.4f}")