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Cleanup search #77

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merged 2 commits into from
Aug 31, 2023
Merged

Cleanup search #77

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e6bbc76
Cleanup search function
dmeybohm Aug 28, 2023
75fe8fc
Make ostream convert consistent with asString for board code
dmeybohm Aug 31, 2023
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5 changes: 1 addition & 4 deletions engine/src/board_code.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -144,10 +144,7 @@ namespace wisdom

auto operator<< (std::ostream& os, const BoardCode& code) -> std::ostream&
{
os << "{ bits: ";
for (const auto& bits : code.my_pieces)
os << bits;
os << ", metadata: " << code.my_metadata << " }";
os << code.asString();
return os;
}

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80 changes: 38 additions & 42 deletions engine/src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,12 @@ namespace wisdom

void iterate (Color side, int depth);

void search (const Board& parent_board, Color side, int depth, int alpha, int beta);
// Search for the best move, and return the best score.
int search (const Board& parent_board, Color side, int depth,
int alpha, int beta);

[[nodiscard]] auto synthesizeResult() const -> SearchResult;
// Get the best result the search found.
[[nodiscard]] auto getBestResult() const -> SearchResult;

[[nodiscard]] auto moveTimer() const -> not_null<const MoveTimer*>
{
Expand All @@ -42,16 +45,12 @@ namespace wisdom
Board my_original_board;
History my_history;
not_null<observer_ptr<const Logger>> my_output;
SearchResult my_current_result {};
MoveGenerator my_generator {};
MoveTimer my_timer;

int my_total_depth;
int my_search_depth {};

optional<Move> my_best_move = nullopt;
int my_best_depth = -1;
int my_best_score = -1;
bool my_timed_out = false;

int my_nodes_visited = 0;
int my_alpha_beta_cutoffs = 0;
int my_total_nodes_visited = 0;
Expand All @@ -71,7 +70,7 @@ namespace wisdom
IterativeSearch::iterativelyDeepen (Color side)
{
impl->iterativelyDeepen (side);
return impl->synthesizeResult();
return impl->getBestResult();
}

auto IterativeSearch::isCancelled() -> bool
Expand All @@ -90,19 +89,21 @@ namespace wisdom
return current_color == searching_color ? Min_Draw_Score : 0;
}

void IterativeSearchImpl::search (const Board& parent_board, // NOLINT(misc-no-recursion)
Color side, int depth, int alpha, int beta)
int IterativeSearchImpl::search (const Board& parent_board, // NOLINT(misc-no-recursion)
Color side, int depth, int alpha, int beta)
{
std::optional<Move> best_move {};
int best_score = -Initial_Alpha;

auto moves = my_generator.generateAllPotentialMoves (parent_board, side);
for (auto move : moves)
{
int score;

if (my_timer.isTriggered())
{
my_timed_out = true;
return;
my_current_result.timed_out = true;
return -Initial_Alpha;
}

Board child_board = parent_board.withMove (side, move);
Expand All @@ -118,30 +119,27 @@ namespace wisdom
{
if (isDrawingMove (child_board, side, move, my_history))
{
my_best_score = drawingScore (my_searching_color, side);
score = drawingScore (my_searching_color, side);
}
else
{
my_best_score = evaluate (child_board, side,
my_search_depth - depth, my_generator);
score = evaluate (child_board, side,
my_search_depth - depth, my_generator);
}
}
else
{
// Don't recurse into a big search if this move is a draw.
if (my_search_depth == depth && isDrawingMove (child_board, side, move, my_history))
{
my_best_score = drawingScore (my_searching_color, side);
score = drawingScore (my_searching_color, side);
}
else
{
search (child_board, colorInvert (side), depth-1, -beta, -alpha);
my_best_score *= -1;
score = -1 * search (child_board, colorInvert (side), depth-1, -beta, -alpha);
}
}

int score = my_best_score;

if (score > best_score)
{
best_score = score;
Expand All @@ -153,8 +151,8 @@ namespace wisdom

my_history.removeLastTentativePosition();

if (my_timed_out)
return;
if (my_current_result.timed_out)
return -Initial_Alpha;

if (alpha >= beta)
{
Expand All @@ -163,17 +161,17 @@ namespace wisdom
}
}

auto result = SearchResult { best_move, best_score,
my_search_depth - depth, false };

my_best_move = result.move;
if (!my_best_move.has_value())
my_current_result.depth = my_search_depth - depth;
if (!best_move.has_value())
{
// if there are no legal moves, then the current player is in a stalemate or checkmate position.
result.score = evaluateWithoutLegalMoves (parent_board, side, result.depth);
// if there are no legal moves, then the current player is in a
// stalemate or checkmate position.
best_score = evaluateWithoutLegalMoves (parent_board, side,
my_current_result.depth);
}
my_best_score = result.score;
my_best_depth = result.depth;
my_current_result.move = best_move;
my_current_result.score = best_score;
return best_score;
}

static void calc_time (const Logger& output, int nodes, system_clock_t start, system_clock_t end)
Expand All @@ -188,7 +186,7 @@ namespace wisdom

void IterativeSearchImpl::iterativelyDeepen (Color side)
{
SearchResult best_result = SearchResult::from_initial();
SearchResult best_result {};
my_searching_color = side;

try
Expand All @@ -203,10 +201,10 @@ namespace wisdom
my_output->info (ostr.str());

iterate (side, depth);
if (my_timed_out)
if (my_current_result.timed_out)
break;

auto next_result = synthesizeResult();
auto next_result = getBestResult();
if (next_result.move.has_value())
{
best_result = next_result;
Expand All @@ -215,9 +213,7 @@ namespace wisdom
}
}

my_best_score = best_result.score;
my_best_move = best_result.move;
my_best_depth = best_result.depth;
my_current_result = best_result;
return;
}
catch (const Error &e)
Expand All @@ -228,10 +224,9 @@ namespace wisdom
}
}

[[nodiscard]] auto IterativeSearchImpl::synthesizeResult() const -> SearchResult
[[nodiscard]] auto IterativeSearchImpl::getBestResult() const -> SearchResult
{
return SearchResult { my_best_move,
my_best_score, my_best_depth, my_timed_out };
return my_current_result;
}

void IterativeSearchImpl::iterate (Color side, int depth)
Expand All @@ -246,11 +241,12 @@ namespace wisdom
auto start = std::chrono::system_clock::now();

my_search_depth = depth;
my_current_result = SearchResult {};
search (my_original_board, side, depth, -Initial_Alpha, Initial_Alpha);

auto end = std::chrono::system_clock::now();

auto result = synthesizeResult();
auto result = getBestResult();

calc_time (*my_output, my_nodes_visited, start, end);

Expand Down
14 changes: 4 additions & 10 deletions engine/src/search.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,16 +16,10 @@ namespace wisdom

struct SearchResult
{
optional<Move> move;
int score;
int depth;
bool timed_out;

static SearchResult from_initial() noexcept
{
SearchResult result { nullopt, -Initial_Alpha, 0, false };
return result;
}
int score = -Initial_Alpha;
int depth { 0 };
optional<Move> move { nullopt };
bool timed_out { false };
};

class IterativeSearch
Expand Down
35 changes: 35 additions & 0 deletions engine/test/board_code_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

#include <algorithm>
#include <iostream>
#include <sstream>

#include "board_code.hpp"
#include "coord.hpp"
Expand Down Expand Up @@ -141,6 +142,40 @@ TEST_CASE( "board code")
}
}

TEST_CASE( "Board code can be converted" )
{
SUBCASE( "to a string" )
{
std::stringstream stream;
BoardCode code = BoardCode::fromEmptyBoard();

code.addPiece(
coordParse("h1"),
ColoredPiece::make(Color::White, Piece::King)
);

auto result = code.asString().substr(0, 4);

CHECK( result == "0110" );
}

SUBCASE( "to an ostream" )
{
std::stringstream stream;
BoardCode code = BoardCode::fromEmptyBoard();

code.addPiece(
coordParse("h1"),
ColoredPiece::make(Color::White, Piece::King)
);

stream << code;
auto result = stream.str().substr(0, 4);

CHECK( result == "0110" );
}
}

TEST_CASE( "Board code stores metadata" )
{
SUBCASE( "Board code stores en passant state for Black" )
Expand Down