Fixes minor bug in IterativeDeepeningEngine

Author: fathzer

README.md

@@ -21,6 +21,8 @@ This doesn't means that the AI can't be used to play Reversi. Simply, the revers
 ## TODO (probable breaking changes)
 - com.fathzer.games.ai.AbstractAI requires an ExecutionContext in its constructor. I think this is not a good approach (even it was mine ;-)) to have this non standard implementation detail exposed outside this public class. Moreover, this disallow building different multi-threading models in AI implementation. Typically it is currently impossible to use a fork/join pool to perform the search.
 As it seems, in real life, a new context is created at each AI invocation, a better approach would be to let the AI manage its own threading scheme, and simply pass a SearchContext to the constructor.
+- Some methods in `TranspositionTable` and `com.fathzer.games.ai/iterativedeepening` implicitly suppose that the move generator implement `HashProvider`. This may be changed for an explicit requirement.
+
 
 ## TODO (maybe)
 - Make MoveLibrary implement AI?

src/main/java/com/fathzer/games/ai/iterativedeepening/IterativeDeepeningEngine.java

@@ -5,6 +5,7 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
 
+import com.fathzer.games.HashProvider;
 import com.fathzer.games.MoveGenerator;
 import com.fathzer.games.ai.Negamax;
 import com.fathzer.games.ai.SearchContext;
@@ -267,8 +268,10 @@ protected IterativeDeepeningSearch<M> doSearch(B board, List<M> searchedMoves) {
 				rs.setEventLogger(logger);
 				rs.setSearchedMoves(searchedMoves);
 				final List<EvaluatedMove<M>> result = rs.getSearchHistory().getAccurateMoves();
-				for (EvaluatedMove<M> ev:result) {
-					ev.setPvBuilder(m -> getTranspositionTable().collectPV(board, m, deepeningPolicy.getDepth()));
+				if (board instanceof HashProvider) {
+					for (EvaluatedMove<M> ev:result) {
+						ev.setPvBuilder(m -> getTranspositionTable().collectPV(board, m, deepeningPolicy.getDepth()));
+					}
 				}
 				logger.logSearchEnd(board, rs.getSearchHistory());
 				return rs;