How do I use the analysis output of a UCI engine? I'm trying to analyze some of my games with the Stockfish UCI engine.  I'd like to make sure I'm interpreting the output correctly.  Using this screenshot as an example.



Can someone explain to me all of the output? Such as.

What does this line tell me?


  20 [-1.13]  7.c3 Bg4 8.h3 Bxf3 9.Qxf3 bxa4 (8.39)


What does this line tell me?


  [-1.33] Depth: 27/40 Nodes: 550933K (4130 kn/s) Time: 133.41 s
  NPS: 4129627 Hash: ---- Load: ---- TB hits: ---- Current: c3 (1/25)


If the first number is centipawns why does it continue to analyze positions that seem to give me a worse position?
It is showing you the results of the analysis for each depth it gets to, sometimes more than once per depth (I think those are upper/lower bound scores, actually). So at depth 20 it thought the best move was -1.13 pawns, and at depth 27 it now knows it's really -1.33 pawns (according to its evaluation).

I like to use the multi-pv setting (click the up spinner next to V++ to increase the number of root moves to analyze), which gives you a good overall perspective of your different options (you can compare c3 and Nc3, for example).