Stuck with my chess project

[nova wharf]

I'm currently building an API that fetches chess games from Chess.com. The goal is to analyze these games using Stockfish in order to identify all mistakes and blunders.

The problem I'm facing now is that it's difficult to reliably detect mistakes in the games, because the evaluation I get back from Stockfish isn't consistent or trustworthy enough.

What I do is send each move to Stockfish, which returns an evaluation for the given position. I then calculate the evaluation difference between consecutive moves, and if the difference exceeds a certain threshold, I classify it as a mistake or blunder.

However, the issue is that even after just two opening moves (e4 e5), Stockfish sometimes returns an evaluation of +1.06, which is clearly unreasonable at such an early stage in a balanced opening.

So I'm currently unsure how to move forward. I haven’t found any other APIs that can analyze PGN-format games reliably, but I know there are websites that provide similar analysis, so there must be a way to do it.

How should I proceed?

[cold plover]

<@&987246399047479336> please have a look, thanks.

[covert parrot]

Stockfish is the norm and is the best engine out there
So if you get something like that, it means you did something wrong

[nova wharf]

im not doing anything wrong, this is taken from their api https://stockfish.online/

with depth 15 and this FEN rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2

In other words, after 1. e4 e5. its impossible its +1.06

[covert parrot]

Why not host stockfish directly ?

[covert parrot]

i tried to run stockfish in local, got +0.11

[nova wharf]

what do you mean host directly? do you have a link with documentation?

and i think i also got 0.11 with depth 12

[covert parrot]

Yes, go to their website, click download

It seems that there is something wrong with this api

And since they don't give any info about the setting or the version of stock fish they are using

It's better to download stock fish directly and use it in local

[nova wharf]

Okay, I’ll check that out. Maybe this is straightforward, but can my API use Stockfish locally? I mean, my idea is to eventually host this on a website or app, would it still be possible to use a locally downloaded and running version of Stockfish?

The reason I used the Stockfish API instead was because I didn’t know it was possible to run the same engine locally.

[chilly sable]

pretty sure chess.com and lichess run stockfish locally on the user's device. You could check how lichess does it: https://lichess.org/source. https://github.com/hi-ogawa/Stockfish looks notable, also https://github.com/lichess-org/stockfish.js. This could be useful for the fronted: https://github.com/lichess-org/lila/tree/master/ui/analyse

I dont know how lichess does it, so you can look at the source code for it or wait for someone who already knows to tell you

[covert parrot]

if you host it on a website ? what is the problem ?
you would have a server anyway

[misty ruin]

Yeah you would just run your API and the Stockfish app on the same server, and instead of requesting Stockfish's API you communicate with the local service (i.e., localhost) instead. Should work fundementally the same, you just need to use another host in your network requests.

[nova wharf]

Thank you! I think I now have a better understanding of how to move forward with my project and what I need to look into next