Extending Skill to 0...40 instead to -20...20

I would avoid negative skill levels and just extend the skill level to 0...40 instead to -20...20

Changes need for Skill 0...40 an still having UCI_Elo 0....3000


In search.cpp

Line 203: // Skill structure is used to implement strength limit

 struct Skill {
   explicit Skill(int l) : level(l) {}
   bool enabled() const { return level < 40; }
   bool time_to_pick(Depth depth) const { return depth == 1 + level; }
   Move pick_best(size_t multiPV);

   int level;
   Move best = MOVE_NONE;
 };

Line 453: 

 double floatLevel = Options["UCI_LimitStrength"] ?
                      std::clamp((Options["UCI_Elo"] - 1500.0) / 37.5, 0.0, 40.0) :
                        double(Options["Skill Level"]);

Line 2100 : int weakness = 120 - level;

In UCIOption.cpp;

Line 71:  o["Skill Level"]           << Option(40, 0, 40);

ddugovic / Stockfish

Extending Skill to 0...40 instead to -20...20 #589