src/mine_memorized.py

"""
Memorization Mining

Utilities for finding memorized sequences from training data.

Based on: "From Memorization to Reasoning in the Spectrum of Loss Curvature"
"""

import torch
import torch.nn as nn
from torch import Tensor
from typing import Optional, Iterator
from dataclasses import dataclass
import json
from tqdm import tqdm
import random


@dataclass
class MemorizedSequence:
    """A memorized sequence with prefix and suffix."""
    
    prefix: str
    suffix: str
    prefix_ids: list[int]
    suffix_ids: list[int]
    source: str = ""  # Dataset source
    
    def to_dict(self) -> dict:
        return {
            "prefix": self.prefix,
            "suffix": self.suffix,
            "prefix_ids": self.prefix_ids,
            "suffix_ids": self.suffix_ids,
            "source": self.source,
        }
    
    @classmethod
    def from_dict(cls, d: dict) -> "MemorizedSequence":
        return cls(**d)


def sample_sequences(
    dataset_name: str,
    tokenizer,
    num_sequences: int = 10000,
    prefix_len: int = 64,
    suffix_len: int = 48,
    min_text_tokens: int = None,
    seed: int = 42,
    streaming: bool = True,
    dataset_config: Optional[str] = "en",  # Default to English for C4
    text_column: str = "text",
) -> list[MemorizedSequence]:
    """
    Sample candidate (prefix, suffix) pairs from a dataset.
    
    The sequences are drawn by:
    1. Streaming text from the dataset
    2. Tokenizing each text
    3. Extracting windows of (prefix_len + suffix_len) tokens
    
    Args:
        dataset_name: HuggingFace dataset name
        tokenizer: Tokenizer for the model
        num_sequences: Number of sequences to sample
        prefix_len: Length of prefix in tokens
        suffix_len: Length of suffix in tokens
        min_text_tokens: Minimum tokens in text to be considered
        seed: Random seed
        streaming: Use streaming mode
        dataset_config: Dataset configuration/subset
        text_column: Name of the text column
    
    Returns:
        List of MemorizedSequence candidates
    """
    from datasets import load_dataset
    
    random.seed(seed)
    
    total_len = prefix_len + suffix_len
    min_text_tokens = min_text_tokens or total_len + 10
    
    # Load dataset
    if dataset_config:
        ds = load_dataset(dataset_name, name=dataset_config, split="train", streaming=streaming)
    else:
        ds = load_dataset(dataset_name, split="train", streaming=streaming)
    
    if streaming:
        ds = ds.shuffle(buffer_size=10000, seed=seed)
    
    sequences = []
    seen_prefixes = set()  # For deduplication
    
    pbar = tqdm(total=num_sequences, desc="Sampling sequences")
    
    for example in ds:
        if len(sequences) >= num_sequences:
            break
        
        # Get text
        text = example.get(text_column)
        if not text:
            continue
        
        # Tokenize
        tokens = tokenizer.encode(text, add_special_tokens=False)
        
        if len(tokens) < min_text_tokens:
            continue
        
        # Sample a random window
        max_start = len(tokens) - total_len
        if max_start <= 0:
            continue
        
        start_idx = random.randint(0, max_start)
        
        prefix_ids = tokens[start_idx:start_idx + prefix_len]
        suffix_ids = tokens[start_idx + prefix_len:start_idx + total_len]
        
        # Deduplicate by prefix
        prefix_tuple = tuple(prefix_ids)
        if prefix_tuple in seen_prefixes:
            continue
        seen_prefixes.add(prefix_tuple)
        
        # Decode back to text
        prefix = tokenizer.decode(prefix_ids)
        suffix = tokenizer.decode(suffix_ids)
        
        sequences.append(MemorizedSequence(
            prefix=prefix,
            suffix=suffix,
            prefix_ids=prefix_ids,
            suffix_ids=suffix_ids,
            source=dataset_name,
        ))
        
        pbar.update(1)
    
    pbar.close()
    return sequences


@torch.no_grad()
def check_memorization_batch(
    model: nn.Module,
    tokenizer,
    sequences: list[MemorizedSequence],
    strict: bool = True,
) -> list[tuple[MemorizedSequence, bool, float]]:
    """
    Check if a batch of sequences is memorized.
    
    Args:
        model: Language model
        tokenizer: Tokenizer
        sequences: List of sequences to check
        strict: If True, require exact match; if False, use overlap threshold
    
    Returns:
        List of (sequence, is_memorized, overlap_score) tuples
    """
    model.eval()
    device = next(model.parameters()).device
    
    # Prepare batch
    prefixes = [seq.prefix for seq in sequences]
    suffix_lengths = [len(seq.suffix_ids) for seq in sequences]
    max_suffix_len = max(suffix_lengths)
    
    # Tokenize prefixes
    encoded = tokenizer(
        prefixes,
        return_tensors="pt",
        padding=True,
        truncation=True,
    )
    input_ids = encoded["input_ids"].to(device)
    attention_mask = encoded["attention_mask"].to(device)
    
    # Generate
    from .evaluate import generate_greedy
    generated = generate_greedy(
        model, input_ids, max_suffix_len,
        attention_mask=attention_mask,
        pad_token_id=tokenizer.pad_token_id,
    )
    
    results = []
    for i, (seq, gen_ids) in enumerate(zip(sequences, generated)):
        gen_list = gen_ids.tolist()[:len(seq.suffix_ids)]
        target_list = seq.suffix_ids
        
        # Check match
        is_exact = gen_list == target_list
        
        # Compute overlap
        matches = sum(g == t for g, t in zip(gen_list, target_list))
        overlap = matches / len(target_list) if target_list else 0
        
        is_memorized = is_exact if strict else (overlap >= 0.75)
        
        results.append((seq, is_memorized, overlap))
    
    return results


def filter_memorized(
    model: nn.Module,
    tokenizer,
    candidates: list[MemorizedSequence],
    batch_size: int = 8,
    strict: bool = True,
    progress_bar: bool = True,
) -> list[MemorizedSequence]:
    """
    Filter candidates to keep only memorized sequences.
    
    Args:
        model: Language model
        tokenizer: Tokenizer
        candidates: List of candidate sequences
        batch_size: Batch size for inference
        strict: Require exact match
        progress_bar: Show progress bar
    
    Returns:
        List of memorized sequences
    """
    memorized = []
    
    iterator = range(0, len(candidates), batch_size)
    if progress_bar:
        iterator = tqdm(iterator, desc="Filtering memorized")
    
    for batch_start in iterator:
        batch_end = min(batch_start + batch_size, len(candidates))
        batch = candidates[batch_start:batch_end]
        
        results = check_memorization_batch(model, tokenizer, batch, strict)
        
        for seq, is_mem, overlap in results:
            if is_mem:
                memorized.append(seq)
    
    return memorized


def mine_memorized_sequences(
    model: nn.Module,
    tokenizer,
    dataset_name: str = "allenai/c4",
    target_count: int = 1000,
    max_candidates: int = 50000,
    prefix_len: int = 64,
    suffix_len: int = 48,
    batch_size: int = 8,
    seed: int = 42,
    dataset_config: Optional[str] = "en",  # Default to English for C4
    strict: bool = True,
) -> list[MemorizedSequence]:
    """
    Mine memorized sequences from training data.
    
    This is the main pipeline for finding sequences that the model
    has memorized verbatim.
    
    Args:
        model: Language model
        tokenizer: Tokenizer
        dataset_name: HuggingFace dataset name (should be training data)
        target_count: Desired number of memorized sequences
        max_candidates: Maximum candidates to sample
        prefix_len: Prefix length in tokens
        suffix_len: Suffix length in tokens
        batch_size: Batch size for inference
        seed: Random seed
        dataset_config: Dataset configuration
        strict: Require exact match
    
    Returns:
        List of memorized sequences
    """
    print(f"Mining memorized sequences from {dataset_name}")
    print(f"Target: {target_count} memorized, max candidates: {max_candidates}")
    
    # Sample candidates
    print("\nStep 1: Sampling candidates...")
    candidates = sample_sequences(
        dataset_name=dataset_name,
        tokenizer=tokenizer,
        num_sequences=max_candidates,
        prefix_len=prefix_len,
        suffix_len=suffix_len,
        seed=seed,
        dataset_config=dataset_config,
    )
    print(f"Sampled {len(candidates)} candidates")
    
    # Filter for memorized
    print("\nStep 2: Filtering for memorized sequences...")
    memorized = filter_memorized(
        model=model,
        tokenizer=tokenizer,
        candidates=candidates,
        batch_size=batch_size,
        strict=strict,
    )
    
    print(f"\nFound {len(memorized)} memorized sequences "
          f"({len(memorized)/len(candidates)*100:.1f}% of candidates)")
    
    # Truncate if we found more than needed
    if len(memorized) > target_count:
        random.seed(seed)
        memorized = random.sample(memorized, target_count)
        print(f"Truncated to {target_count} sequences")
    
    return memorized


def save_sequences(sequences: list[MemorizedSequence], path: str) -> None:
    """Save sequences to a JSON file."""
    data = [seq.to_dict() for seq in sequences]
    with open(path, "w") as f:
        json.dump(data, f, indent=2)
    print(f"Saved {len(sequences)} sequences to {path}")


def load_sequences(path: str) -> list[MemorizedSequence]:
    """Load sequences from a JSON file."""
    with open(path, "r") as f:
        data = json.load(f)
    sequences = [MemorizedSequence.from_dict(d) for d in data]
    print(f"Loaded {len(sequences)} sequences from {path}")
    return sequences


def split_sequences(
    sequences: list[MemorizedSequence],
    train_ratio: float = 0.8,
    seed: int = 42,
) -> tuple[list[MemorizedSequence], list[MemorizedSequence]]:
    """
    Split sequences into train and validation sets.
    
    Args:
        sequences: List of sequences
        train_ratio: Fraction for training set
        seed: Random seed
    
    Returns:
        Tuple of (train_sequences, val_sequences)
    """
    random.seed(seed)
    shuffled = sequences.copy()
    random.shuffle(shuffled)
    
    split_idx = int(len(shuffled) * train_ratio)
    train = shuffled[:split_idx]
    val = shuffled[split_idx:]
    
    return train, val


def get_prefixes_and_suffixes(
    sequences: list[MemorizedSequence],
) -> tuple[list[str], list[str]]:
    """
    Extract prefix and suffix strings from sequences.
    
    Useful for passing to evaluation functions.
    """
    prefixes = [seq.prefix for seq in sequences]
    suffixes = [seq.suffix for seq in sequences]
    return prefixes, suffixes


# Historical quotes dataset (for out-of-distribution testing)
HISTORICAL_QUOTES = [
    # Famous quotes that models often memorize
    ("To be, or not to be, that is the question:", " Whether 'tis nobler in the mind to suffer"),
    ("Four score and seven years ago our fathers brought forth", " on this continent, a new nation, conceived in Liberty"),
    ("I have a dream that one day this nation will rise up", " and live out the true meaning of its creed"),
    ("Ask not what your country can do for you", " — ask what you can do for your country"),
    ("The only thing we have to fear is", " fear itself"),
    ("In the beginning God created", " the heavens and the earth"),
    ("It was the best of times, it was the worst of times,", " it was the age of wisdom, it was the age of foolishness"),
    ("Call me Ishmael. Some years ago—never mind how long precisely", "—having little or no money in my purse"),
    ("All happy families are alike; each unhappy family is", " unhappy in its own way"),
    ("It is a truth universally acknowledged, that a single man in possession", " of a good fortune, must be in want of a wife"),
]


def create_quotes_dataset(
    tokenizer,
    additional_quotes: Optional[list[tuple[str, str]]] = None,
) -> list[MemorizedSequence]:
    """
    Create a dataset of historical quotes for OOD memorization testing.
    
    Args:
        tokenizer: Tokenizer
        additional_quotes: Additional (prefix, suffix) tuples to include
    
    Returns:
        List of MemorizedSequence objects
    """
    quotes = HISTORICAL_QUOTES.copy()
    if additional_quotes:
        quotes.extend(additional_quotes)
    
    sequences = []
    for prefix, suffix in quotes:
        prefix_ids = tokenizer.encode(prefix, add_special_tokens=False)
        suffix_ids = tokenizer.encode(suffix, add_special_tokens=False)
        
        sequences.append(MemorizedSequence(
            prefix=prefix,
            suffix=suffix,
            prefix_ids=prefix_ids,
            suffix_ids=suffix_ids,
            source="historical_quotes",
        ))
    
    return sequences