// --------------------------------------------------------------------------------------------
static void ProcessNode(PositionEvalCache cache, MCTSNode node, float weightEmpirical,
bool saveToCache, bool rewriteNodeInTree)
{
Span <MCTSNodeStructChild> children = node.Ref.Children;
// TODO: optimize this away if saveToCache is false
ushort[] probabilities = new ushort[node.NumPolicyMoves];
ushort[] indices = new ushort[node.NumPolicyMoves];
// Compute empirical visit distribution
float[] nodeFractions = new float[node.NumPolicyMoves];
for (int i = 0; i < node.NumChildrenExpanded; i++)
{
nodeFractions[i] = (float)node.ChildAtIndex(i).N / (float)node.N;
}
// Determine P of first unexpanded node
// We can't allow any child to have a new P less than this
// since we need to keep them in order by P and the resorting logic below
// can only operate over expanded nodes
float minP = 0;
if (node.NumChildrenExpanded < node.NumPolicyMoves)
{
minP = node.ChildAtIndexInfo(node.NumChildrenExpanded).p;
}
// Add each move to the policy vector with blend of prior and empirical values
for (int i = 0; i < node.NumChildrenExpanded; i++)
{
(MCTSNode node, EncodedMove move, FP16 p)info = node.ChildAtIndexInfo(i);
indices[i] = (ushort)info.move.IndexNeuralNet;
float newValue = (1.0f - weightEmpirical) * info.p
+ weightEmpirical * nodeFractions[i];
if (newValue < minP)
{
newValue = minP;
}
probabilities[i] = CompressedPolicyVector.EncodedProbability(newValue);
if (rewriteNodeInTree && weightEmpirical != 0)
{
MCTSNodeStructChild thisChild = children[i];
if (thisChild.IsExpanded)
{
ref MCTSNodeStruct childNodeRef = ref thisChild.ChildRef;
thisChild.ChildRef.P = (FP16)newValue;
}
else
{
node.Ref.ChildAtIndex(i).SetUnexpandedPolicyValues(thisChild.Move, (FP16)newValue);
}
}
}
/// <summary>
/// Implements the gathering of nodes up to speecified maximum depth and width.
/// </summary>
/// <param name="selectorID"></param>
/// <param name="node"></param>
/// <param name="maxNodes"></param>
/// <param name="maxDepth"></param>
/// <param name="width"></param>
/// <param name="nodes"></param>
/// <param name="pThreshold"></param>
void GatherRootPreloadNodes(int selectorID, MCTSNode node, int maxNodes, int maxDepth, int width, List <MCTSNode> nodes, float pThreshold)
{
if (nodes.Count >= maxNodes)
{
return;
}
if (node.IsTranspositionLinked)
{
return;
}
// For each top child
for (int i = 0; i < Math.Min(node.NumPolicyMoves, width); i++)
{
if (NumPreloaded >= MAX_PRELOAD_NODES_TOTAL)
{
return;
}
(MCTSNode childNode, EncodedMove move, FP16 p) = node.ChildAtIndexInfo(i);
if (float.IsNaN(pThreshold) || p >= pThreshold)
{
// Add this node if not already extant
if (childNode == null)
{
// Create this child (as cache only) and update in flight
childNode = node.CreateChild(i);
childNode.ActionType = MCTSNode.NodeActionType.CacheOnly;
if (selectorID == 0)
{
childNode.Ref.BackupIncrementInFlight(1, 0);
}
else
{
childNode.Ref.BackupIncrementInFlight(0, 1);
}
nodes.Add(childNode);
NumPreloaded++;
if (nodes.Count == maxNodes)
{
return;
}
}
else
{
node.Annotate();
if (node.Depth < maxDepth - 1 && childNode.N > 0)
{
// Recursively descend
Debug.Assert(childNode != null);
GatherRootPreloadNodes(selectorID, childNode, maxNodes, maxDepth, width, nodes, pThreshold);
}
}
}
}
}
void OutputUCIInfo(MCTSManager manager, MCTSNode searchRootNode, bool isFinalInfo = false)
{
BestMoveInfo best = searchRootNode.BestMoveInfo(false);
if (numPV == 1)
{
UCIWriteLine(UCIInfo.UCIInfoString(manager, searchRootNode, best?.BestMoveNode,
showWDL: showWDL, scoreAsQ: scoreAsQ));
}
else
{
// Send top move
UCIWriteLine(UCIInfo.UCIInfoString(manager, searchRootNode, best.BestMoveNode, 1,
showWDL: showWDL, useParentN: !perPVCounters, scoreAsQ: scoreAsQ));
// Send other moves visited
MCTSNode[] sortedN = searchRootNode.ChildrenSorted(s => - (float)s.N);
int multiPVIndex = 2;
for (int i = 0; i < sortedN.Length && i < numPV; i++)
{
if (!object.ReferenceEquals(sortedN[i], best.BestMoveNode))
{
UCIWriteLine(UCIInfo.UCIInfoString(manager, searchRootNode, sortedN[i], multiPVIndex,
showWDL: showWDL, useParentN: !perPVCounters, scoreAsQ: scoreAsQ));
multiPVIndex++;
}
}
// Finally show moves that had no visits
float elapsedTimeSeconds = (float)(DateTime.Now - manager.StartTimeThisSearch).TotalSeconds;
string timeStr = $"{ elapsedTimeSeconds * 1000.0f:F0}";
for (int i = multiPVIndex - 1; i < searchRootNode.NumPolicyMoves; i++)
{
(MCTSNode node, EncodedMove move, FP16 p)info = searchRootNode.ChildAtIndexInfo(i);
if (info.node == null)
{
bool isWhite = searchRootNode.Annotation.Pos.MiscInfo.SideToMove == SideType.White;
EncodedMove moveCorrectPerspective = isWhite ? info.move : info.move.Flipped;
string str = $"info depth 0 seldepth 0 time { timeStr } nodes 1 score cp 0 tbhits 0 "
+ $"multipv {multiPVIndex} pv {moveCorrectPerspective.AlgebraicStr} ";
UCIWriteLine(str);
multiPVIndex++;
}
}
}
if (verboseMoveStats && (logLiveStats || isFinalInfo))
{
OutputVerboseMoveStats(CeresEngine.Search.SearchRootNode);
}
}
static MCTSNode DescendMovesToNode(MCTSNode rootNode, List <MGMove> moves)
{
MCTSNode node = rootNode;
foreach (MGMove move in moves)
{
int?childIndex = node.Ref.ChildIndexWithMove(move);
if (childIndex is null)
{
throw new Exception($"Move {move} not found at node {node}");
}
else
{
(node, _, _) = node.ChildAtIndexInfo(childIndex.Value);
}
}
return(node);
}
public static List <LC0VerboseMoveStat> BuildStats(MCTSNode searchRootNode)
{
List <LC0VerboseMoveStat> stats = new List <LC0VerboseMoveStat>();
BestMoveInfo best = searchRootNode.BestMoveInfo(false);
// First process policy moves not yet expanded
// starting from last one (lowest probability).
for (int i = searchRootNode.NumPolicyMoves - 1; i >= 0; i--)
{
(MCTSNode node, EncodedMove move, FP16 p)info = searchRootNode.ChildAtIndexInfo(i);
if (info.node == null)
{
LC0VerboseMoveStat stat = BuildStatNotExpanded(searchRootNode, i);
stats.Add(stat);
}
}
// Now process moves expanded in order of visit count.
MCTSNode[] sortedN = searchRootNode.ChildrenSorted(s => (float)s.N + 0.0001f * s.P);
foreach (MCTSNode node in sortedN)
{
if (!object.ReferenceEquals(node, best.BestMoveNode))
{
stats.Add(BuildStatExpanded(node, false));
}
}
// Save the best move for last.
stats.Add(BuildStatExpanded(best.BestMoveNode, false));
// Finally, output the search root node.
stats.Add(BuildStatExpanded(searchRootNode, true));
return(stats);
}
