Computer analysis - 2

What, exactly, do the plus and minus numbers mean in the computer analysis? 

Where do these specific numbers come from?

Are they all my scores even if an analysis is being made of my opponent's move?

If nothing is said about a move, why does the score change?

Thank you in advance.

Computers score a game in units of pawns. The score is a combination of material count and positional count. The computer tries to figure out the best sequence of moves for each side by evaluating the resulting positions at the end of the sequence. The score for the current position is the evaluation of the best play for both sides at the end of a certain depth.

Evaluation is only an estimate. As a result, which moves are best play is also an estimate.

The score will change from move to move for a few reasons. You may have made a move that wasn't the best move. This might not get a comment from the computer if it was close enough to the best move. Also, the computer can only search to a certain depth. One move later it can search one move farther, so the score estimate can chage.

Also, a + score is an advantage to white, while a - score is an advantage to black. So it doesn't matter who is on the move, the score is saying, in general, who is winning with that particular move.

By a certain depth, Loomis, do you mean a certain number of moves ahead?

"The score for the current position is the evaluation of the best play for both sides at the end of a certain depth."

So, Martin, if the computer gives a score for my move and I'm playing black, and that score is -1.3, I'm being told I've gained on this?  Is this correct?

"Also, a + score is an advantage to white, while a - score is an advantage to black. So it doesn't matter who is on the move, the score is saying, in general, who is winning with that particular move."

Not to answer for Loomis, but a certain # of moves ahead matches the ply of the engine, or possibly less if there is a forced series of moves in the variation being evalutated. So, based on your other topic, 5 moves deep, or 10-ply from the current move being evaluated for the Chess.com engine you are using.

The score is not for the move, the score is for the position.

Yes, if a move shows as -1.3 that essentially means that black is winning by 1.3 pawns. If ther previous move evaluation was smaller in magnitude, say -.5, then you can say you move, or your opponents, improved your lead. At least, that is in the engines evaluation, limited by the depth it actually searches (ply depth).

 Why not to answer for Loomis, Martin?  (Please note my smilies and laughies.)  I teach college online and love it when various of my students answer for other ones (I'm not saying anyone here is a student of mine -- absolutely not as I'm a student of yours).  What you're seeing here is what my classroom looks like.  I'm in my comfort zone. :)))))

Yes, that is more accurate. Though it is the position based on the move being evaluated.

 I think I understand this now.  Thank you both very much for your help in this and the other threads!