Remove v2 data and add v4 data (#345)

Will need to test readding v2 and adding more v4. 

Passed STC
```
Test  | v4no2
Elo   | 3.07 +- 2.23 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=16MB
LLR   | 2.98 (-2.94, 2.94) [0.00, 3.00]
Games | N: 31764 W: 7894 L: 7613 D: 16257
Penta | [369, 3756, 7365, 4009, 383]
```
https://clockworkopenbench.pythonanywhere.com/test/1054/

Passed LTC
```
Test  | v4no2
Elo   | 1.76 +- 1.42 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=64MB
LLR   | 2.95 (-2.94, 2.94) [0.00, 3.00]
Games | N: 65936 W: 15302 L: 14968 D: 35666
Penta | [411, 7644, 16456, 8114, 343]
```
https://clockworkopenbench.pythonanywhere.com/test/1055/

Bench: 14055228

Author: TheRealGioviok

.gitignore

@@ -46,4 +46,7 @@ build*/
 books/*
 
 # Spsa output for script usage
-spsa_out*.txt
+spsa_out*.txt
+
+# Venv folder for python scripts
+venv/

scripts/extract-data.py

@@ -1,29 +1,28 @@
-import os
 import random
+import io
 from pathlib import Path
-from concurrent.futures import ThreadPoolExecutor, as_completed
-from typing import List, Optional
+from concurrent.futures import ProcessPoolExecutor, as_completed
+from typing import List
 import chess
 import chess.pgn
-import io
 from tqdm import tqdm
 
 
+# ------------------------------------------------------------
+# Game logic
+# ------------------------------------------------------------
 
 def is_capture_or_promotion(board: chess.Board, move: chess.Move) -> bool:
-    """Check if a move is a capture or promotion."""
     return board.is_capture(move) or move.promotion is not None
 
 
 def extract_positions_from_game(game_data: str, n_positions: int = 5) -> List[str]:
-    """Extract N sampled positions from a game, with original restrictions, labeled with final result (w/d/b)."""
     try:
         pgn_io = io.StringIO(game_data)
         game = chess.pgn.read_game(pgn_io)
         if not game:
             return []
 
-        # Map result to label
         result = game.headers.get("Result", "")
         if result == "1-0":
             outcome = "w"
@@ -32,27 +31,22 @@ def extract_positions_from_game(game_data: str, n_positions: int = 5) -> List[st
         elif result == "1/2-1/2":
             outcome = "d"
         else:
-            return []  # Skip unfinished/invalid games
+            return []
 
         board = game.board()
         valid_positions = []
-        move_number = 0
 
-        # Iterate through all moves in the game
         for node in game.mainline():
             move = node.move
             if move:
                 board.push(move)
-                move_number += 1
 
-            # Skip if in check or no legal moves
             if board.is_check() or not any(board.legal_moves):
                 continue
 
             next_node = node.next()
             best_move = next_node.move if next_node else None
 
-            # Skip if best move is capture or promotion
             if best_move and is_capture_or_promotion(board, best_move):
                 continue
 
@@ -61,7 +55,6 @@ def extract_positions_from_game(game_data: str, n_positions: int = 5) -> List[st
         if not valid_positions:
             return []
 
-        # Randomly select up to n_positions
         if len(valid_positions) > n_positions:
             valid_positions = random.sample(valid_positions, n_positions)
 
@@ -71,115 +64,130 @@ def extract_positions_from_game(game_data: str, n_positions: int = 5) -> List[st
         return []
 
 
-def count_games_in_file(file_path: Path) -> int:
-    try:
-        with open(file_path, "r", encoding="utf-8") as f:
-            content = f.read()
-        return content.count("[Event ")
-    except Exception:
-        return 0
+def process_single_game(game_data: str, positions_per_game: int) -> List[str]:
+    return extract_positions_from_game(game_data, positions_per_game)
 
 
-def process_pgn_file(file_path: Path, positions_per_game: int = 5, pbar: Optional[tqdm] = None) -> List[str]:
-    results = []
-    try:
-        with open(file_path, "r", encoding="utf-8") as f:
-            content = f.read()
-
-        games = []
-        current_game = []
-        for line in content.split("\n"):
-            if line.strip().startswith("[Event ") and current_game:
-                games.append("\n".join(current_game))
-                current_game = [line]
+# ------------------------------------------------------------
+# PGN streaming utilities
+# ------------------------------------------------------------
+
+def stream_pgn_games(file_path: Path):
+    with open(file_path, "r", encoding="utf-8") as f:
+        game_lines = []
+        for line in f:
+            if line.startswith("[Event ") and game_lines:
+                yield "".join(game_lines)
+                game_lines = [line]
             else:
-                current_game.append(line)
-        if current_game:
-            games.append("\n".join(current_game))
-
-        for game_data in games:
-            if game_data.strip():
-                positions = extract_positions_from_game(game_data, positions_per_game)
-                results.extend(positions)
-            if pbar:
-                pbar.update(1)
+                game_lines.append(line)
 
-    except Exception as e:
-        print(f"Error processing file {file_path}: {e}")
-        if pbar:
-            expected_games = count_games_in_file(file_path)
-            pbar.update(expected_games)
+        if game_lines:
+            yield "".join(game_lines)
 
-    return results
+
+def count_games_in_file(file_path: Path) -> int:
+    count = 0
+    with open(file_path, "r", encoding="utf-8") as f:
+        for line in f:
+            if line.startswith("[Event "):
+                count += 1
+    return count
 
 
-def extract_positions_from_folder(folder_path: str, positions_per_game: int = 5, max_workers: int = 4) -> List[str]:
+# ------------------------------------------------------------
+# Main multiprocessing pipeline
+# ------------------------------------------------------------
+
+def extract_positions_from_folder(
+    folder_path: str,
+    positions_per_game: int = 5,
+    max_workers: int = 4,
+    task_buffer: int = 2000,
+) -> List[str]:
+
     folder = Path(folder_path)
     if not folder.exists():
-        raise FileNotFoundError(f"Folder {folder_path} does not exist")
+        raise FileNotFoundError(f"Folder does not exist: {folder}")
 
     pgn_files = list(folder.glob("*.pgn"))
     if not pgn_files:
-        print(f"No PGN files found in {folder_path}")
+        print("No PGN files found.")
         return []
 
     print(f"Found {len(pgn_files)} PGN files")
 
-    total_games = 0
-    for pgn_file in tqdm(pgn_files, desc="Counting games"):
-        total_games += count_games_in_file(pgn_file)
-
+    total_games = sum(count_games_in_file(p) for p in pgn_files)
     print(f"Total games to process: {total_games}")
 
     all_results = []
-    with tqdm(total=total_games, desc="Processing games", unit="games") as pbar:
-        with ThreadPoolExecutor(max_workers=max_workers) as executor:
-            future_to_file = {
-                executor.submit(process_pgn_file, pgn_file, positions_per_game, pbar): pgn_file
-                for pgn_file in pgn_files
-            }
-            for future in as_completed(future_to_file):
-                try:
-                    all_results.extend(future.result())
-                except Exception as e:
-                    print(f"Error: {e}")
+    futures = []
+
+    with ProcessPoolExecutor(max_workers=max_workers) as executor:
+        with tqdm(total=total_games, desc="Processing games", unit="games") as pbar:
+
+            for pgn_file in pgn_files:
+                for game_data in stream_pgn_games(pgn_file):
+                    futures.append(
+                        executor.submit(
+                            process_single_game,
+                            game_data,
+                            positions_per_game,
+                        )
+                    )
+
+                    if len(futures) >= task_buffer:
+                        for future in as_completed(futures):
+                            all_results.extend(future.result())
+                            pbar.update(1)
+                        futures.clear()
+
+            for future in as_completed(futures):
+                all_results.extend(future.result())
+                pbar.update(1)
 
     return all_results
 
 
-def save_positions_to_file(positions: List[str], output_file: str = "sampled_positions.txt"):
+# ------------------------------------------------------------
+# Output
+# ------------------------------------------------------------
+
+def save_positions_to_file(positions: List[str], output_file: str):
     with open(output_file, "w", encoding="utf-8") as f:
         for line in positions:
             f.write(line + "\n")
     print(f"Saved {len(positions)} positions to {output_file}")
 
 
+# ------------------------------------------------------------
+# CLI
+# ------------------------------------------------------------
+
 def main():
     folder_path = input("Enter the path to the folder containing PGN files: ").strip()
+
     try:
         positions_per_game = int(input("Enter number of positions per game (default 5): ") or "5")
     except ValueError:
         positions_per_game = 5
 
     try:
-        max_workers = int(input("Enter maximum number of worker threads (default 4): ") or "4")
+        max_workers = int(input("Enter maximum number of worker processes (default 4): ") or "4")
     except ValueError:
         max_workers = 4
 
-    try:
-        positions = extract_positions_from_folder(
-            folder_path, positions_per_game=positions_per_game, max_workers=max_workers
-        )
-        if positions:
-            output_file = f"sampled_positions_{len(positions)}.txt"
-            save_positions_to_file(positions, output_file)
-            print(f"\nSummary:")
-            print(f"- Total positions saved: {len(positions)}")
-            print(f"- File: {output_file}")
-        else:
-            print("No valid games found!")
-    except Exception as e:
-        print(f"Error: {e}")
+    positions = extract_positions_from_folder(
+        folder_path,
+        positions_per_game=positions_per_game,
+        max_workers=max_workers,
+    )
+
+    if positions:
+        output_file = f"sampled_positions_{len(positions)}.txt"
+        save_positions_to_file(positions, output_file)
+    else:
+        print("No positions extracted.")
 
 
 if __name__ == "__main__":
@@ -188,7 +196,7 @@ def main():
         import chess.pgn
         from tqdm import tqdm
     except ImportError:
-        print("Please install required dependencies:")
+        print("Please install dependencies:")
         print("pip install python-chess tqdm")
         exit(1)