* Contempt OP (opening phase), Contempt MG (for middlegame) and Contempt EG (yes, for endgame) allow to subtract or add some points to the basic contempt (range -200 to 200) and work only for appropriate phase of game. It means when You set, we can say (-20) for opening (and opening would be set to 15 limit) - it makes engine more defensive for first 15 moves but in 16 move its score will change (effect of contempt OP will disappear or - if set - will be changed to next contempt MG and so on).
* Next 15 options - Pawn OP to Queen EG refer of course to set phases of game. Range -100 to 100 allows to add or subtract material worth of each piece. 1 point is more or less 1 percent (not exactly due to psqt tables and other things but it's easier to treat it this way). It's easy to guess that if only opening threshold is set then MG and EG values do nothing even if changed.
It works in different way than Exchange options. Exchange options tell engine that there is some loss or gain in specific exchanging/saving piece on chessboard, it directly affects score. Changes in range Pawn OP to Queen EG aren't so noticeable at first in engine score output (so btw don't require compensate by contempt like exchange), tell engine rather that it should care less or more for picked piece in picked range of moves.
Example: (-20) in Pawn OP makes engine to play more positional in opening, at the expense of pawns, so is more likely to pick some gambit lines with sacrifices of pawns like "B01 Scandinavian (centre counter) defence".
Second example: High value in Knight MG (we can try 30) makes engine to searching (in middlegame) for lines where it saves its knights and "kill" opponent knight with exchanging for bishop for example. It works this way because engine assumes that not only its knights are worth more than bishops but opponent's knights too.
Generally negative values make engine more positional/tactic at the expense of material and opposite - higher positive values make it more materialistic and more blind for tactic and positional play. So it won't be surprise if effect of many higher values in material will bring position where engine has one or two pawns more (even as black) but its position will be scored negative and it ll be going to lose game.
ThothFish v. 1.2 isn't best option for people who looking for already tuned derivative which is slightly better than Stockfish, because with default options (exchange and material set to 0) it plays with the same strength as Stockfish. It's rather created for people who like looking for new ways to gain elo or change play style of engine by switching options on one’s own.
So there is no point (with default options) for testing it against other derivatives unless one's figure out which options and how much to change, then testing could be worthy and interesting.
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Quick fix. ThothFish v1.21. I assume that some people would prefer to have normal engine output in infinite analysis mode so I made version 1.21 and in this version expanded analysis is optional (option "DeepAnalysis" to check in uci menu).
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