Does the Stockfish engine use past matches, or does it not need such a "database"?

Question

I have a simple question. Does the Stockfish engine use, amongst the steps of its complicated algorithm, a library/database of past matches? For such an algorithm to work, it would to need store many matches that have had a particular scenario. Each scenario has a player who went on to win. Thus, it is provided some kind of rating point to judge each particular scenario with, allowing it to choose the best move. It's either that or the Stockfish engine works just by working through the possible moves to figure out how to win.

In other words, does the Stockfish engine need to be fed data from past matches or can it work without any such data ?

Answer 1

Technically, Stockfish does make use of past matches, just not when it's playing. The way it uses its past matches is during training, when a new neural network (NNUE in Stockfish's case) is being trained. Once the NNUE is trained, though, it is "standalone" and does not change anymore.

The Stockfish you can download and play has an already-trained NNUE, so it does not use past matches.

Answer 2

does the Stockfish engine need to be fed data from past matches

No.

You are confusing Stockfish with AlphaZero. The two engines work in entirely different ways.

Stockfish works by using brute force calculation plus clever evaluation functions to determine what is the best move in any position. During a game it maintains hash tables of positions and evaluations that have occurred during that game so that when it calculates a transposition of an earlier calculated position it doesn't redo the calculations but just uses the previous one.

If an opening database is available it can use that but it also works perfectly well albeit slower without. Similarly in the endgame it can use tablebases if available which can greatly increase speed and accuracy.

AlphaZero, however, does work off a database of positions and evaluations which are generated during a "training" phase.