Get top moves at each depth

[thedemons]

Added the generate_top_moves method which returns a generator that yields top moves in the position at every depth.

This helps evaluate the position at a high depth and update the interface simultaneously. The evaluation could be stopped by calling Generator.close().

Breaking changes:

• The list returned by the generator is now a list of Stockfish.TopMove class instead of a list of dict. This is necessary for sorting the list of top moves without writing a custom sort algorithm.
• The centipawn and mate values are now relative to the turn, they are the same values as returned from stockfish.

Notice:

• Top moves returned while evaluating are sorted by mate first, then depth, then centipawn.
• The depth, while evaluating, could go backward, e.g. the next depth could be lower than the previous depth.
• Stopping the evaluation can take some time, it sends the stop command to stockfish and waits for the bestmove to be returned to continue execution.

Example usage:

Simple usage:

for top_moves in stockfish.generate_top_moves():
    best_move = top_moves[0]
    print(f"Best move at depth {best_move.depth}: {best_move.move}")

Stop the evaluation early:

gen = stockfish.generate_top_moves()
try:
    while True:
        top_moves = next(gen)
        best_move = top_moves[0]
        print(f"Best move at depth {best_move.depth}: {best_move.move}")

        if best_move.depth == 5:
            gen.close() # stop the evaluation
            break

except StopIteration:
    print("Finished evaluation")

With this simple method added, you can do some pretty neat stuff like this:

[johndoknjas]

I think this would be a great feature to have in the module!