Why do some TT problems not have source and analysis? Can somebody please analyze problem 0024927? I solved it only to realize from the comments that the solution wasn't much of a solution. It is not at all obvious how White is winning after "solving" the problem.

Some of the Tactics Trainer problems do not have the source and analysis but as you said you can always get further feedback by posting questions in the comments section for that specific Tactics Trainer problem.

feedback and some commentary posted now.

http://www.chess.com/tactics/server.html?id=24927

regards,

Thanks for the commentary over at that problem. I'm curious though as to the technical side of how TT works. I would have guessed that the source and analysis was not just an extra part of most problems, but was an essential part that drove the engine. Every problem needs a PGN or equivalent to provide the initial position, move order, and when to stop. The source provides that. So all I can think is that there are some problems which have a source but no annotations in that source. Is that right? Were such problems some of the very first ones for TT? I understand that today all of the problem submissions are mechanically processed and automatically get a computer analysis. Thanks.

yes, basically, that is how it works.

Typically:   the computer generates the evaluation (lines), the pgn file shows 2 or 3 (usually 3) best lines for each move, selects the 'best' move' for each side, after the first move by the defender (a defective move in some way), and then posts the materials to a file.

      the tactics moderators review them to ensure: 

a. no move for the side assigned allows multiple mates; 

b. the difference between best move and second best is always at least 2.5 points difference (although that can be a little subjective, it is usually the standard).

c. the tactic reaches a logical conclusion (logical for a human).  Since moderators are human (some might think otherwise), and their experience is varied, as are the engines used to validate tactics when the moderator chooses to, errors can happen.

     An additional feature:  crafty generated analysis is NOT always right, so don't hesitate to post a question if you find confusion in the solution.

WHEN you find one with no analysis, that merely means a moderator (human) determined the tactic was defective in some way, and rather than remove it, modified the FEN or the PGN file and didn't provide analysis - possibly because the tactic was taken from a tactics book, and presumed to be correct, or because his engine didn't allow extracting the analysis, (or just lazy).  Occasionally a moderator will post one of those that is defective, and when that happens, we discuss the issue 'offline' (privately), and remove it or modify it again.

    moderators appreciate users who look into the analysis before posting a thoughtful question.   Most questions are good ones, because if you are wondering, likely so are others.    However, there are always users who post nonsense questions or comments;    such as:  "first"  or  "easy"  or "too hard for this rating"; or never look into the analysis and still persist in posting other quite irrelevant comments and frequently misleading by their failure to take some reasonable action, such as look into the analysis lines with a board.

    one user, amused by the posts, has compiled the more inane ones into the "tactics Strainer" - his blog posts.     see contributions on his profile view by user       joe_blob 

regards,