SCID vs PC

Thanks, ill check it out.

How do I add engines to Scid vs pc.

ive looked through the help files but its very technical. 

i would like to adds stockfish DD to it.

thank you

Go to Tools -> Analysis Engines, click on New, type in Name, e.g. Stockfish DD, click on Browse and select stockfish exe file. You can also select Hot key, e.g. F4. Make sure Protocol is UCI and click OK. That's it.

Thats great. thanks cavelorum

Ive been analyzing the following position with Scid vs Pc(stockfish)

It first selected 6.Nc3 as best next move for white.

when i chose a different move and then took it back i ran the analysis again in the same position(above) and it then recommended 6.Bg5 followed by 6.Nxc6 as next best move.

Why does it change its analysis.

thanks again

i see that the moves are good.

what i want to know is why does scid vs pc change its preference of best move

The short of it is - Stockfish has changed it's best move because it has now seen further ahead :)

Interestingly, some GUIs do their engine analysis (annotation) starting from the end move, and working backwards - i suppose because the stored lines are more relevant - but i'm not really knowledgable/sure that it should be done this way.

Not to answer the question directly, but the difference in strength and/or accuracy of the moves is largely irrelevant for humans.  These lines are analyzed over 20 moves ahead - far beyond what we are able to handle in complex positions, and tiny differences in positional strength are meaningless unless playing against another engine.  They would require absolute accuracy to realize any beneficial difference in human play.  I would consider it a positive feature giving you a choice of "best" moves. 

Why the engine varies may stem from cached analysis.  Try closing your GUI and restarting it and then run it again and see if you don't get the same result.

Steven's answer is correct.  When the engine chose a different move the second time, it's most likely you simply had it look at the position for a longer period of time, even as little as a second or two.  The evaluation will change constantly, as it looks deeper and deeper into the position.

I'm having Stockfish DD look at the position, with my PV set to 3, and these are the three top moves I see, at a ply of 27:

1. 27 [+0.44]  6.Nc3 Be7 7.O-O O-O 8.a3 Nxd4 9.Qxd4 Be6 10.Bf4 Nd7 11.Nd5 Bf6 12.Nxf6+ Qxf6 13.Qxf6 Nxf6 14.Bd3 Nd7 15.Rfe1 Ne5 16.Be2 Rae8 17.f3 Bd7 18.Kf2 f5 19.Bxe5

2. 27 [+0.26]  6.O-O Ne5 7.Bb3 Be7 8.Nc3 O-O 9.Bf4 c5 10.Nf3 Ng6 11.Be3 Be6 12.Qe2 Ng4 13.Bc1 Re8 14.Rd1 a6 15.h3 N4e5 16.Nxe5 Nxe5

3. 27 [+0.28]  6.Bb5 Bd7 7.Nc3 Be7 8.Nxc6 Bxc6 9.Qd3 O-O 10.O-O Nd7 11.Bxc6 Ne5 12.Qe2 Nxc6 13.Be3 Bf6 14.Nd5 Re8 15.f3 Bxb2 16.Rab1

Notice that Nxc6 isn't one of the top three choices at all.  (But it was a ply earlier.  Bb5 replaced it.)   Depending upon your own processor speed, available ram, hash settings, etc., the top three moves you see may be different, even at the same ply level.

As I type this, it's now at ply 29.  It still likes the above three moves as best, in that same order, but with a different evaluation score.  At level 29 it likes 0-0 just as much (+0.40) as Nc3.

Thanks lads, heres what I see using StockfishDD.  

The highest evaluated move is at number 6 which is 0-0 +.98pt.  

If choosing a move purely on what engine thinks would I choose what it gives at Number 1 or choose Number 6 or choose Number 27 when it has searched deeper.

If you are preparing an opening computer should be an aid but not an oracle. Try moves which come to your head (so you understand them better) and see if there is a tactical refutation.

Also, try the database functions of Scid vs PC (http://icofy-blog.de/ offers 5 million games databases in Scid format for free). With the tree option you can see what others played in a particular position and if you try something out of that tree you will likely find a novelty.

You can dig deeper into variations by either looking at engine's best choices and trying out your own ideas. If there is no tactical flow you can try to practice those lines in real games. It is more likely you remember moves that you find most natural than those recommended by engines.

Anyway, there is no big difference between +0.4 and +0.15 - with Stockfish you have to know that its evaluation is scaled and +2.5 is a score that should be considered winning, for <2.5 there is still chance of holding the position by the weaker side. There were nTCEC games where Stockfish was not able to convert +2.4 or defended -2.4

In general to compare evaluation of a position by Stockfish and Houdini you should divide Stockfish eval by 2 (or even 3). Do not get too excited when SF shows e.g. +1.5 - this means there is advantage but not that huge as +1.5 for Houdini, Rybka or Komodo.

You have single PV mode on, it is just giving one move fore each search depth. As the dearch depth chamges, the evaluation changes, and sometimes even the move changes.

If you change to multi PV mode, your display will change.

You can do that by changing the number 1 to something else, (3 or 4 is best, IMO) next to the +V icon at the top

Thanks again, I dont use stockfish to select my moves. i always choose my own.  i just use it to see what other potential moves there are and what i should have played.

Atm im using it to understand openings im trying in Online Chess.

I was then wondering why it changes its thinking by selecting different best moves.

I have another problem.

ive just analyzed a full game with stockfish.

the analysis finished and the screen showed this

i then clicked the pgn tab expecting to see the analysis annotation added to the pgn but all i see is the list of moves with no analysis annotation

what am i doing wrong.

Your first image suggests you have not clicked "Annotate" button (the one after the lock).

Without that, you can just look at engine analysis but nothing is saved.

I want to clarify what rooperi already responded to.

In post #416, you said the highest evaluated move is at #6 and asked if you should chose what it gives at #1 or #6 or #27.

You have your PV (Principal Variation) set to 1.  When you have it set to 1, you always look at the very bottom move.  That's the move it thinks is best and that's the evaluation score it now gives that position. 

When you have your PV set to 1, the engine will list, at each ply, the move and  the entire line of play it thinks is best, for both sides.

In your example, it initially liked Nc3, with a score of +0.94.  As it continued to look at that position, then it liked castling, then it liked Nc3 again, then it liked Nxc6 and finally it decided that Nc3 was best, but now only with a score of +0.36.  It's now looked at this position to a depth of 27 ply.    

So even though it did like 0-0 for a moment, at depth 5 with a score of +1.03, as it looked deeper and deeper into the position, the engine now realizes +1,03 is NOT the true evaluation of this position, nor is 0-0 the best move.  So no, you wouldn't want to chose 0-0.  The engine searched deeper and adjusted it's evaluation of the position.

However, as others have pointed out, moves that have small differences in evaluations are, for all practicaly purposes, the same.  Nxc6, with an evaluation of +0.42 is going to be just as good as a move that has an evaluation of +0,40, for example.

Try setting your PV to 3.  The screen will only show the top three moves, and this might be easier to understand.

I did click it. thats the problem

[quote]i then clicked the pgn tab expecting to see the analysis annotation added to the pgn but all i see is the list of moves with no analysis annotation[/quote]

I'm guessing, somehow you've somehow reloaded the game. PGN is read-only, and any game changes are discarded transparently. Best to work with si4 or the clipbase.

PS - to get rid of the white line in the gameinfo, deselect Options->GameInfo->ShowPhotos.

Make sure the board shows the start position before you start analysing. If you're at end of game it wont do anything.

Can someone tell me step by step what they do when they want to analyse a PGN of a game that they played on Chess.com with Stockfish.

What I do is this

1 get PGN from game archive in Chess.com

2 load Pgn in Scid vs Pc

3 go to Tools-Analysis Engines-Start

4 Hit the Annotate button beside Lock

5 wait for game to finish

I'm Using Scid, not Scid vs PC. But I repeat, add to yoyr step 2, make sure the board shows the start position. When you import a pgn into Scid, the default is the final position.