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Adding LowestElo and HighestElo constants

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These values represent the lowest Elo rating in the skill level calculation,
and the highest one, but it's not clear from the code where these values come
from other than the comment.  This should improve code readability and
maintainability. It makes the purpose of the values clear and allows for easy
modification if the Elo range for skill level calculation changes in the
future.  Moved the Skill struct definition from search.cpp to search.h header
file to define the Search::Skill struct, making it accessible from other files.

closes https://github.com/official-stockfish/Stockfish/pull/5508

No functional change
This commit is contained in:
FauziAkram 2024-07-21 18:52:26 +03:00 • committed by Joost VandeVondele
parent a2ba3e3362
commit 986173264f
3 changed files with 32 additions and 26 deletions
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4
src/engine.cpp
View file

@ -91,7 +91,9 @@ Engine::Engine(std::string path) :
options["nodestime"] << Option(0, 0, 10000);
options["UCI_Chess960"] << Option(false);
options["UCI_LimitStrength"] << Option(false);
options["UCI_Elo"] << Option(1320, 1320, 3190);
options["UCI_Elo"] << Option(Stockfish::Search::Skill::LowestElo,
Stockfish::Search::Skill::LowestElo,
Stockfish::Search::Skill::HighestElo);
options["UCI_ShowWDL"] << Option(false);
options["SyzygyPath"] << Option("", [](const Option& o) {
Tablebases::init(o);

25
src/search.cpp
View file

@ -94,31 +94,6 @@ int stat_malus(Depth d) { return std::min(736 * d - 268, 2044); }
// Add a small random component to draw evaluations to avoid 3-fold blindness
Value value_draw(size_t nodes) { return VALUE_DRAW - 1 + Value(nodes & 0x2); }
// Skill structure is used to implement strength limit. If we have a UCI_Elo,
// we convert it to an appropriate skill level, anchored to the Stash engine.
// This method is based on a fit of the Elo results for games played between
// Stockfish at various skill levels and various versions of the Stash engine.
// Skill 0 .. 19 now covers CCRL Blitz Elo from 1320 to 3190, approximately
// Reference: https://github.com/vondele/Stockfish/commit/a08b8d4e9711c2
struct Skill {
Skill(int skill_level, int uci_elo) {
if (uci_elo)
{
double e = double(uci_elo - 1320) / (3190 - 1320);
level = std::clamp((((37.2473 * e - 40.8525) * e + 22.2943) * e - 0.311438), 0.0, 19.0);
}
else
level = double(skill_level);
}
bool enabled() const { return level < 20.0; }
bool time_to_pick(Depth depth) const { return depth == 1 + int(level); }
Move pick_best(const RootMoves&, size_t multiPV);
double level;
Move best = Move::none();
};
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply, int r50c);
void update_pv(Move* pv, Move move, const Move* childPv);

29
src/search.h
View file

@ -19,6 +19,7 @@
#ifndef SEARCH_H_INCLUDED
#define SEARCH_H_INCLUDED
#include <algorithm>
#include <array>
#include <atomic>
#include <cassert>
@ -180,6 +181,34 @@ struct InfoIteration {
size_t currmovenumber;
};
// Skill structure is used to implement strength limit. If we have a UCI_Elo,
// we convert it to an appropriate skill level, anchored to the Stash engine.
// This method is based on a fit of the Elo results for games played between
// Stockfish at various skill levels and various versions of the Stash engine.
// Skill 0 .. 19 now covers CCRL Blitz Elo from 1320 to 3190, approximately
// Reference: https://github.com/vondele/Stockfish/commit/a08b8d4e9711c2
struct Skill {
// Lowest and highest Elo ratings used in the skill level calculation
constexpr static int LowestElo = 1320;
constexpr static int HighestElo = 3190;
Skill(int skill_level, int uci_elo) {
if (uci_elo)
{
double e = double(uci_elo - LowestElo) / (HighestElo - LowestElo);
level = std::clamp((((37.2473 * e - 40.8525) * e + 22.2943) * e - 0.311438), 0.0, 19.0);
}
else
level = double(skill_level);
}
bool enabled() const { return level < 20.0; }
bool time_to_pick(Depth depth) const { return depth == 1 + int(level); }
Move pick_best(const RootMoves&, size_t multiPV);
double level;
Move best = Move::none();
};
// SearchManager manages the search from the main thread. It is responsible for
// keeping track of the time, and storing data strictly related to the main thread.
class SearchManager: public ISearchManager {