Stockfish Is Your Friend

This post will discuss the engine Stockfish:

• How to invoke it
• What information is presented
• How to interpret the display
• How to avoid being misled
• Why you shouldn't follow its recommendations blindly
• How to use it for the Daily Puzzle

People make reference to "the engine" frequently.  What is it?  And what the heck is "Stockfish"?

The engine is a computer algorithm optimized for chess.  There are many out there [you may be familiar with Deep Blue, the computer that beat Gary Kasparov in the 90s; since then, computers have gotten way stronger].  "Stockfish" is the name of the engine used by chess.com.

The engine is a wonderful tool for analysis and self-improvement.  it does have some pitfalls, which I'll address later.

Note:   every registered user, whether a subscriber or not, has access to the engine.  The extras like the game graph, classification of moves, accuracy, etc. are available in the Game Review and non-subscribers have a limited number [3?] whereas premium members have more [depending on level of membership].

This is an example:

However, even with just the basic engine output, it's a fantastic analysis tool.

First off, open the engine:

Note that you have to finish a puzzle in order to get the engine icon to appear.

Here's the daily puzzle from 2023/04/25:

Here is Stockfish's analysis:

Starting from the top right:

"depth" is a measure of how deeply the engine calculates.  Level 20 [default] takes about 30 seconds.  Level 22 takes about 60 seconds.  And level 99 takes an infinite amount of time.  Stick with the default for now.

"Stockfish" is the default engine; you can also use Komodo.

The gear wheel to the right allows you to change settings.  I never have tweaked these.

On the left are 3 slider buttons:

• Evaluation:  the bar on the far left indicating who is winning
• Lines:  whether to show the top 3 lines or just the solution
• Feedback:  a description of the move [ie "Best", "Excellent", "Inaccuracy", etc]

In this example, the engine shows who the players were [if it states "White" and "Black" then it's a composed puzzle, unless the players' names were actually White and Black; even cooler would be if player White had the Black pieces.  Otherwise, it will show players names].

By default, it lists the top 3 lines.

• + is White winning; - is Black winning
• The numerical portion is by how much is one side winning
• Mx is checkmate:  "+" for White; "-" for Black.  "x" is how many moves

So in this example, the top line is +M5:  Checkmate in 5 moves for White.

The next line is +3.42, a 3.42 advantage for White.

The next line is -0.18, a 0.18 advantage for Black.

The numbers correspond roughly to material so +1 means being up a pawn, +3 means being up a piece, etc.  But remember, it doesn't work the other way around:  just because you're up a piece doesn't mean the engine will necessarily say your position is 3.  You could be losing because you're about to get checkmated.

Also, when choosing between two lines, don't necessarily assume the higher # is "better":  the engine doesn't care about play style.  It could judge line 1 to be +5 and line 2 to be +4 but you much prefer line 2 because it matches your play style.

So caveat emptor on taking everything the engine states as gospel.  You still need to interpret what it's stating.

You can also click on any given move sequence and follow it.  Note that the eval will change over the course of moves.  Evals are not static.

You can use the navigation buttons to move your way through the puzzle

and there are many features on the bottom:

I'll cover these in a separate post.

The great thing is you can play any move you want and the engine will recalculate its evaluation.  So if you play a completely terrible move, the +M5 will vanish, replaced by a horribly negative score.

For example, I played 1. bxa4?? in this position and the engine dutifully reported [this is only available in an engine analysis of your position, which I think you get one free per day if you are a non-member; but the numerical evaluations are free in unlimited quantity]:

• My move was a mistake and the new eval -3.32
• What I should have played
• The top 3 lines [I don't know why the top eval disagrees with the bottom one]

If people would use this feature, they could answer their own question "Why doesn't move X work?" and we wouldn't get the same question asked and answered 87 times daily.  One can only hope.