static void Search(
State root,
MtdfIds searcher,
GoSettings settings,
Program program,
CancellationToken ct)
{
ISearchInfo info;
{
using var _ = searcher.IterationCompleted.Subscribe(icInfo =>
{
// todo: even if we have cached tt info, we should be outputting the full pv
// todo: output other info fields (see stockfish)
var output = $"info depth {icInfo.Depth} time {(int)icInfo.Elapsed.TotalMilliseconds} nodes {icInfo.NodesSearched} score cp {icInfo.Score} pv {string.Join(' ', icInfo.Pv)}";
WriteLine(output);
});
info = searcher.Search(root, ct);
}
// if we finished but we're in ponder or infinite mode, wait until we receive "ponderhit" or "stop"
while (!ct.IsCancellationRequested && (settings.Infinite || program._ponder))
{
Thread.Sleep(500);
}
// output the best move. if the pv contains more than 1 move (eg. there's not a mate in 1 and we searched more than depth 1),
// output that too as the next move we expect the user to play.
Debug.Assert(!info.Pv.IsEmpty);
var output = $"bestmove {info.Pv[0]}";
if (info.Pv.Length > 1)
{
output += $" ponder {info.Pv[1]}";
}
WriteLine(output);
}
void Go(Stack <string> tokens)
{
if (_root == null)
{
Error.WriteLine("Position not set, use the 'position' command to set it");
return;
}
var settings = new GoSettings();
while (tokens.TryPop(out var paramName))
{
switch (paramName)
{
case "searchmoves": // needs to be the last command on the line
var searchMoves = new List <Move>();
while (tokens.TryPop(out var move))
{
searchMoves.Add(Move.ParseLong(move));
}
settings.SearchMoves = searchMoves.ToImmutableArray();
break;
case "ponder":
_ponder = true;
break;
case "depth":
settings.Depth = int.Parse(tokens.Pop());
break;
case "nodes":
settings.Nodes = int.Parse(tokens.Pop());
break;
case "mate": // todo
settings.Mate = int.Parse(tokens.Pop());
break;
case "movetime": // todo
settings.MoveTime = TimeSpan.FromMilliseconds(int.Parse(tokens.Pop()));
break;
case "infinite":
settings.Infinite = true;
break;
}
}
// go ahead with the search
var searcher = new MtdfIds();
searcher.Depth = settings.Depth ?? ((settings.Infinite || settings.Nodes != null) ? int.MaxValue : DefaultSearchDepth);
searcher.MaxNodes = settings.Nodes ?? int.MaxValue;
int ttCapacity = _options.Get <int>("Hash") * EntriesPerMb;
if (_tt == null || _tt.Capacity != ttCapacity)
{
_tt = searcher.MakeTt(ttCapacity);
}
searcher.Tt = _tt;
_ponder = false;
var cts = new CancellationTokenSource();
// define the task and either run it straight away, or add it to the queue if there's one in progress
var rootCopy = _root; // if a new search is requested before this one is started, we don't want to pick up on a new position
var searchTask = new Task(() =>
{
try
{
_cts = cts;
Search(rootCopy, searcher, settings, this, cts.Token);
}
// exceptions don't propagate to the main thread unless they are explicitly handled like this
catch (Exception e)
{
Error.WriteLine(e);
}
finally
{
cts.Dispose();
_cts = null;
// run the next task if one is queued
if (_searchQueue.TryDequeue(out var nextTask))
{
nextTask.Start();
}
else
{
_searchInProgress = false;
}
}
});
if (!_searchInProgress)
{
Debug.Assert(_searchQueue.IsEmpty);
_searchInProgress = true;
searchTask.Start();
}
else
{
_searchQueue.Enqueue(searchTask);
}
}
