Virtual_Visit, Virtual_Mix, Virtual_Offset

engine/CMakeLists.txt

@@ -43,7 +43,7 @@ if (MODE_CHESS)
 #    add_definitions(-DVERSION=2)
 #    add_definitions(-DSUB_VERSION=8)
     add_definitions(-DVERSION=3)
-    add_definitions(-DSUPPORT960)
+#    add_definitions(-DSUPPORT960)
 endif()
 
 if (MODE_LICHESS)
@@ -57,7 +57,7 @@ if (MODE_LICHESS)
     add_definitions(-DATOMIC)
     add_definitions(-DHORDE)
     add_definitions(-DRACE)
-    add_definitions(-DSUPPORT960)
+#    add_definitions(-DSUPPORT960)
     add_definitions(-DMCTS_TB_SUPPORT)
     add_definitions(-DVERSION=1)
 endif()

engine/src/agents/config/searchsettings.cpp

@@ -33,7 +33,6 @@ SearchSettings::SearchSettings():
         nodePolicyTemperature(1.0f),
         qValueWeight(1.0f),
         qVetoDelta(0.4f),
-        virtualLoss(1.0f),
         verbose(true),
         epsilonChecksCounter(100),
         useMCGS(true),
@@ -49,7 +48,10 @@ SearchSettings::SearchSettings():
         epsilonGreedyCounter(20),
         reuseTree(true),
         mctsSolver(false),
-        searchPlayerMode(MODE_TWO_PLAYER)
+        searchPlayerMode(MODE_TWO_PLAYER),
+        virtualStyle(VIRTUAL_VISIT),
+        virtualMixThreshold(1000),
+        virtualOffsetStrenght(0.001)
 {
 
 }

engine/src/agents/config/searchsettings.h

@@ -36,6 +36,13 @@ enum SearchPlayerMode {
     MODE_TWO_PLAYER
 };
 
+enum VirtualStyle {
+    VIRTUAL_LOSS,
+    VIRTUAL_VISIT,
+    VIRTUAL_OFFSET,
+    VIRTUAL_MIX
+};
+
 struct SearchSettings
 {
     uint16_t multiPV;
@@ -48,7 +55,6 @@ struct SearchSettings
     float qValueWeight;
     // describes how much better the highest Q-Value has to be to replace the candidate move with the highest visit count
     float qVetoDelta;
-    uint_fast32_t virtualLoss;
     bool verbose;
     uint_fast8_t epsilonChecksCounter;
 //    bool enhanceCaptures;   currently not support
@@ -75,6 +81,12 @@ struct SearchSettings
     bool mctsSolver;
     // Defines the nubmer of players within the MCTS search. Available are MODE_SINGLE_PLAYER and MODE_TWO_PLAYER
     SearchPlayerMode searchPlayerMode;
+    // Define the virtual style to avoid conflict between different threads in within the same mini-batch
+    VirtualStyle virtualStyle;
+    // Defines the number of visits to switch from virtual-visit to virtual-loss
+    uint_fast32_t virtualMixThreshold;
+    // Defines the strength of the virtual offset
+    double virtualOffsetStrenght;
     SearchSettings();
 
 };

engine/src/node.cpp

@@ -36,9 +36,9 @@ bool Node::is_sorted() const
     return sorted;
 }
 
-double Node::get_q_sum(ChildIdx childIdx, float virtualLoss) const
+double Node::get_q_sum_virtual_loss(ChildIdx childIdx) const
 {
-    return get_child_number_visits(childIdx) * double(get_q_value(childIdx)) + get_virtual_loss_counter(childIdx) * virtualLoss;
+    return get_child_number_visits(childIdx) * double(get_q_value(childIdx)) + get_virtual_loss_counter(childIdx);
 }
 
 bool Node::is_transposition() const
@@ -504,18 +504,28 @@ bool Node::has_nn_results() const
     return hasNNResults;
 }
 
-void Node::apply_virtual_loss_to_child(ChildIdx childIdx, uint_fast32_t virtualLoss)
+void Node::apply_virtual_loss_to_child(ChildIdx childIdx, const SearchSettings* searchSettings)
 {
     // update the stats of the parent node
     // make it look like if one has lost X games from this node forward where X is the virtual loss value
     // temporarily reduce the attraction of this node by applying a virtual loss /
     // the effect of virtual loss will be undone if the playout is over
-    d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] - virtualLoss) / double(d->childNumberVisits[childIdx] + virtualLoss);
+    switch (get_virtual_style(searchSettings, d->childNumberVisits[childIdx])) {
+    case VIRTUAL_LOSS:
+        d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] - 1) / double(d->childNumberVisits[childIdx] + 1);
+        break;
+    case VIRTUAL_OFFSET:
+        d->qValues[childIdx] -= searchSettings->virtualOffsetStrenght;
+    case VIRTUAL_VISIT: ;  // ignore
+    case VIRTUAL_MIX: ;  // unreachable
+    }
+
     // virtual increase the number of visits
-    d->childNumberVisits[childIdx] += virtualLoss;
-    d->visitSum += virtualLoss;
+    ++d->childNumberVisits[childIdx];
+    ++d->visitSum;
+
     // increment virtual loss counter
-    update_virtual_loss_counter<true>(childIdx, virtualLoss);
+    update_virtual_loss_counter<true>(childIdx);
 }
 
 float Node::get_q_value(ChildIdx childIdx) const
@@ -642,20 +652,29 @@ uint32_t Node::get_real_visits(ChildIdx childIdx) const
     return d->childNumberVisits[childIdx] - d->virtualLossCounter[childIdx];
 }
 
-void backup_collision(float virtualLoss, const Trajectory& trajectory) {
+void backup_collision(const SearchSettings* searchSettings, const Trajectory& trajectory) {
     for (auto it = trajectory.rbegin(); it != trajectory.rend(); ++it) {
-        it->node->revert_virtual_loss(it->childIdx, virtualLoss);
+        it->node->revert_virtual_loss(it->childIdx, searchSettings);
     }
 }
 
-void Node::revert_virtual_loss(ChildIdx childIdx, float virtualLoss)
+void Node::revert_virtual_loss(ChildIdx childIdx, const SearchSettings* searchSettings)
 {
     lock();
-    d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] + virtualLoss) / (d->childNumberVisits[childIdx] - virtualLoss);
-    d->childNumberVisits[childIdx] -= virtualLoss;
-    d->visitSum -= virtualLoss;
+    switch (get_virtual_style(searchSettings, d->childNumberVisits[childIdx])) {
+    case VIRTUAL_LOSS:
+        d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] + 1) / (d->childNumberVisits[childIdx] - 1);
+        break;
+    case VIRTUAL_OFFSET:
+        d->qValues[childIdx] += searchSettings->virtualOffsetStrenght;
+    case VIRTUAL_MIX: ; // ignore
+    case VIRTUAL_VISIT: ; // ignore
+    }
+    --d->childNumberVisits[childIdx];
+    --d->visitSum;
+
     // decrement virtual loss counter
-    update_virtual_loss_counter<false>(childIdx, virtualLoss);
+    update_virtual_loss_counter<false>(childIdx);
     unlock();
 }
 
@@ -990,6 +1009,27 @@ void Node::disable_action(size_t childIdxForParent)
     d->qValues[childIdxForParent] = -INT_MAX;
 }
 
+double Node::get_transposition_q_value(const SearchSettings *searchSettings, ChildIdx childIdx, uint_fast32_t transposVisits)
+{
+    double transposQValue;
+    switch(get_virtual_style(searchSettings, d->childNumberVisits[childIdx])) {
+    case VIRTUAL_LOSS:
+        transposQValue = get_q_sum_virtual_loss(childIdx) / transposVisits;
+        break;
+    case VIRTUAL_VISIT:
+        transposQValue = get_q_value(childIdx);
+        break;
+    case VIRTUAL_OFFSET:
+        transposQValue = double(get_q_value(childIdx)) + get_virtual_loss_counter(childIdx) * searchSettings->virtualOffsetStrenght;
+    case VIRTUAL_MIX: ;
+        // unreachable
+    }
+    if (searchSettings->searchPlayerMode == MODE_TWO_PLAYER) {
+        return -transposQValue;
+    }
+    return transposQValue;
+}
+
 void Node::enhance_moves(const SearchSettings* searchSettings)
 {
     //    if (!searchSettings->enhanceChecks && !searchSettings->enhanceCaptures) {
@@ -1295,7 +1335,7 @@ bool is_terminal_value(float value)
     return (value == WIN_VALUE || value == DRAW_VALUE || value == LOSS_VALUE);
 }
 
-float get_transposition_q_value(uint_fast32_t transposVisits, double transposQValue, double targetQValue)
+float get_transposition_backup_value(uint_fast32_t transposVisits, double transposQValue, double targetQValue)
 {
     return std::clamp(transposVisits * (targetQValue - transposQValue) + targetQValue, double(LOSS_VALUE), double(WIN_VALUE));
 }

engine/src/node.h

@@ -84,6 +84,16 @@ struct NodeAndBudget {
         node(node), budget(budget), curState(state) {}
 };
 
+inline VirtualStyle get_virtual_style(const SearchSettings* searchSettings, uint_fast32_t visits) {
+    if (searchSettings->virtualStyle == VIRTUAL_MIX) {
+        if (visits > searchSettings->virtualMixThreshold) {
+            return VIRTUAL_LOSS;
+        }
+        return VIRTUAL_VISIT;
+    }
+    return searchSettings->virtualStyle;
+}
+
 class Node
 {
 private:
@@ -190,28 +200,42 @@ class Node
     void revert_virtual_loss_and_update(ChildIdx childIdx, float value, const SearchSettings* searchSettings, bool solveForTerminal)
     {
         lock();
-        // decrement virtual loss counter
-        update_virtual_loss_counter<false>(childIdx, searchSettings->virtualLoss);
 
         valueSum += value;
         ++realVisitsSum;
 
-        if (d->childNumberVisits[childIdx] == searchSettings->virtualLoss) {
+        if (d->childNumberVisits[childIdx] == 1) {
             // set new Q-value based on return
             // (the initialization of the Q-value was by Q_INIT which we don't want to recover.)
             d->qValues[childIdx] = value;
         }
         else {
             // revert virtual loss and update the Q-value
             assert(d->childNumberVisits[childIdx] != 0);
-            d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] + searchSettings->virtualLoss + value) / d->childNumberVisits[childIdx];
+            uint_fast32_t childRealVisit;
+            double newQVal;
+            switch(get_virtual_style(searchSettings, d->childNumberVisits[childIdx])) {
+            case VIRTUAL_LOSS:
+                d->qValues[childIdx] = (double(d->qValues[childIdx]) * d->childNumberVisits[childIdx] + 1 + value) / d->childNumberVisits[childIdx];
+                break;
+            case VIRTUAL_VISIT:
+                childRealVisit = get_real_visits(childIdx);
+                d->qValues[childIdx] = (double(d->qValues[childIdx]) * childRealVisit + value) / (childRealVisit + 1);
+                break;
+            case VIRTUAL_OFFSET:
+                newQVal = double(d->qValues[childIdx]) + d->virtualLossCounter[childIdx] * searchSettings->virtualOffsetStrenght;
+                newQVal = (newQVal * childRealVisit + value) / (childRealVisit + 1.0);
+                d->qValues[childIdx] = newQVal - ((d->virtualLossCounter[childIdx]-1) * searchSettings->virtualOffsetStrenght);
+            case VIRTUAL_MIX: ;
+                // unreachable
+            }
+
             assert(!isnan(d->qValues[childIdx]));
         }
 
-        if (searchSettings->virtualLoss != 1) {
-            d->childNumberVisits[childIdx] -= size_t(searchSettings->virtualLoss) - 1;
-            d->visitSum -= size_t(searchSettings->virtualLoss) - 1;
-        }
+        // decrement virtual loss counter
+        update_virtual_loss_counter<false>(childIdx);
+
         if (freeBackup) {
             ++d->freeVisits;
         }
@@ -225,7 +249,7 @@ class Node
      * @brief revert_virtual_loss Reverts the virtual loss for a target node
      * @param childIdx Index to the child node to update
      */
-    void revert_virtual_loss(ChildIdx childIdx, float virtualLoss);
+    void revert_virtual_loss(ChildIdx childIdx, const SearchSettings* searchSettings);
 
     bool is_playout_node() const;
 
@@ -259,7 +283,7 @@ class Node
     double get_value_sum() const;
     uint32_t get_real_visits() const;
 
-    void apply_virtual_loss_to_child(ChildIdx childIdx, uint_fast32_t virtualLoss);
+    void apply_virtual_loss_to_child(ChildIdx childIdx, const SearchSettings* searchSettings);
 
     void increment_no_visit_idx();
     void fully_expand_node();
@@ -470,17 +494,17 @@ class Node
      */
     void decrement_number_parents();
 
-    double get_q_sum(ChildIdx childIdx, float virtualLoss) const;
+    double get_q_sum_virtual_loss(ChildIdx childIdx) const;
 
     template<bool increment>
-    void update_virtual_loss_counter(ChildIdx childIdx, float virtualLoss)
+    void update_virtual_loss_counter(ChildIdx childIdx)
     {
         if (increment) {
-            d->virtualLossCounter[childIdx] += virtualLoss;
+            ++d->virtualLossCounter[childIdx];
         }
         else {
             assert(d->virtualLossCounter[childIdx] != 0);
-            d->virtualLossCounter[childIdx] -= virtualLoss;
+            --d->virtualLossCounter[childIdx];
         }
     }
 
@@ -515,6 +539,17 @@ class Node
 
     uint32_t get_number_of_nodes() const;
 
+
+    /**
+     * @brief get_transposition_q_value Returns the Q-value (without virtualLoss) which connects to the transposition node.
+     * The q-Value is also multiplied by -1 if searchSettings->searchPlayerMode == MODE_TWO_PLAYER.
+     * @param currentNode Current node
+     * @param childIdx child index
+     * @param transposVisits Number of visits connecting to the transposition node
+     * @return Q-Value converted to double
+     */
+    double get_transposition_q_value(const SearchSettings* searchSettings, ChildIdx childIdx, uint_fast32_t transposVisits);
+
 private:
     /**
      * @brief reserve_full_memory Reserves memory for all available child nodes
@@ -765,12 +800,12 @@ bool is_terminal_value(float value);
 /**
  * @brief backup_collision Iteratively removes the virtual loss of the collision event that occurred
  * @param rootNode Root node of the tree
- * @param virtualLoss Virtual loss value
+ * @param searchSettings Search settings struct
  * @param trajectory Trajectory on how to get to the given collision
  */
-void backup_collision(float virtualLoss, const Trajectory& trajectory);
+void backup_collision(const SearchSettings* searchSettings, const Trajectory& trajectory);
 
-float get_transposition_q_value(uint_fast32_t transposVisits, double transposQValue, double masterQValue);
+float get_transposition_backup_value(uint_fast32_t transposVisits, double transposQValue, double masterQValue);
 
 /**
  * @brief backup_value Iteratively backpropagates a value prediction across all of the parents for this node.
@@ -788,15 +823,12 @@ void backup_value(float value, const SearchSettings* searchSettings, const Traje
         if (targetQValue != 0) {
             const uint_fast32_t transposVisits = it->node->get_real_visits(it->childIdx);
             if (transposVisits != 0) {
-                const double transposQValue = -it->node->get_q_sum(it->childIdx, searchSettings->virtualLoss) / transposVisits;
-                value = get_transposition_q_value(transposVisits, transposQValue, targetQValue);
+                const double transposQValue = it->node->get_transposition_q_value(searchSettings, it->childIdx, transposVisits);
+                value = get_transposition_backup_value(transposVisits, transposQValue, targetQValue);
             }
         }
-        switch (searchSettings->searchPlayerMode) {
-            case MODE_TWO_PLAYER:
+        if (searchSettings->searchPlayerMode == MODE_TWO_PLAYER) {
                 value = -value;
-            break;
-        case MODE_SINGLE_PLAYER: ;
         }
         freeBackup ? it->node->revert_virtual_loss_and_update<true>(it->childIdx, value, searchSettings, solveForTerminal) :
                    it->node->revert_virtual_loss_and_update<false>(it->childIdx, value, searchSettings, solveForTerminal);
@@ -818,5 +850,4 @@ void backup_value(float value, const SearchSettings* searchSettings, const Traje
  */
 bool is_transposition_verified(const Node* node, const StateObj* state);
 
-
 #endif // NODE_H

engine/src/nodedata.cpp

@@ -52,10 +52,6 @@ void NodeData::reserve_initial_space()
     virtualLossCounter.reserve(initSize);
     nodeTypes.reserve(initSize);
     add_empty_node();
-    if (initSize > 1) {
-        add_empty_node();
-        ++noVisitIdx;
-    }
 }
 
 NodeData::NodeData():