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refactor: migrate OnnxStrategy onto dicechess-engine-scala's JvmApi #18

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Merged
rabestro merged 1 commit into from
Aug 4, 2026
Merged

refactor: migrate OnnxStrategy onto dicechess-engine-scala's JvmApi #18

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2 changes: 1 addition & 1 deletion pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@
<maven.compiler.target>25</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

<dicechess.engine.version>1.10.4</dicechess.engine.version>
<dicechess.engine.version>1.12.0</dicechess.engine.version>
<dicechess.bot-runtime.version>1.0.0</dicechess.bot-runtime.version>
<onnxruntime.version>1.20.0</onnxruntime.version>
<junit.jupiter.version>6.1.2</junit.jupiter.version>
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143 changes: 23 additions & 120 deletions src/main/java/dicechess/bot/OnnxStrategy.java
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Original file line number Diff line number Diff line change
@@ -1,43 +1,26 @@
package dicechess.bot;

import dicechess.engine.domain.FenParser;
import dicechess.engine.domain.GameState;
import dicechess.engine.search.TurnGenerator;
import dicechess.engine.jvmapi.JvmApi;

import lv.id.jc.dicechess.runtime.TurnContext;

import scala.collection.immutable.List;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.System.Logger;
import java.lang.System.Logger.Level;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
* Strategy implementation using an ONNX value model (or fallback engine evaluation)
* over all legal full-turn paths generated by TurnGenerator.
* Strategy implementation using an ONNX value model (or fallback engine evaluation) over every legal full turn
* available from the current position, via the engine's {@link JvmApi} facade.
*
* <p>TurnGenerator returns {@code List[List[Move]]} where {@code Move} is an opaque
* Int with layout: bits 0-5 = destination (to), bits 6-11 = source (from),
* bits 12-15 = flags.</p>
* <p>{@link TurnContext#legalMoves()} is not consulted here: scoring a candidate turn needs the resulting board
* position, not just its UCI tokens, so the engine's own enumeration ({@link JvmApi#legalTurns(GameState)}) has to
* run regardless of whether the platform's inline tree was present.</p>
*/
public class OnnxStrategy implements Strategy {

private static final Logger logger = System.getLogger(OnnxStrategy.class.getName());
private static final MethodHandle MAKE_MOVE_MH;

static {
try {
var clazz = Class.forName("dicechess.engine.domain.Position$package");
var methodType = MethodType.methodType(GameState.class, GameState.class, int.class);
MAKE_MOVE_MH = MethodHandles.lookup().findStatic(clazz, "makeMove_Move", methodType);
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}

private final OnnxEvaluator evaluator;

Expand All @@ -51,120 +34,40 @@ public OnnxStrategy(OnnxEvaluator evaluator) {
}

@Override
public java.util.List<String> chooseMoves(TurnContext context) {
public List<String> chooseMoves(TurnContext context) {
if (context == null || context.dfen() == null || context.dfen().isBlank()) {
logger.log(Level.WARNING, "Received empty or null DFEN context");
return Collections.emptyList();
}

var parseResult = FenParser.parse(context.dfen());
if (parseResult.isLeft()) {
var errorMsg = parseResult.left().toOption().isDefined()
? parseResult.left().toOption().get()
: "Unknown FEN error";
logger.log(Level.ERROR, "Failed to parse DFEN ''{0}'': {1}", context.dfen(), errorMsg);
GameState initialState;
try {
initialState = JvmApi.parseDfen(context.dfen());
} catch (IllegalArgumentException e) {
logger.log(Level.ERROR, "Failed to parse DFEN ''{0}'': {1}", context.dfen(), e.getMessage());
return Collections.emptyList();
}

var initialState = parseResult.toOption().get();
var activeColor = initialState.flags() & 1; // Bit 0 of flags is activeColor (0 = White, 1 = Black)

// TurnGenerator returns List[List[Move]]
@SuppressWarnings("unchecked")
var legalTurnPaths =
(List<List<Object>>) (Object) TurnGenerator.generateAllLegalTurnPaths(initialState);
var activeColor = JvmApi.activeColor(initialState);
var turns = JvmApi.legalTurns(initialState);

if (legalTurnPaths.isEmpty()) {
if (turns.isEmpty()) {
logger.log(Level.INFO, "No legal turn paths available for DFEN: {0}", context.dfen());
return Collections.emptyList();
}

java.util.List<Integer> bestPath = null;
JvmApi.Turn bestTurn = null;
float bestScore = -Float.MAX_VALUE;

for (var pathScala : scala.jdk.javaapi.CollectionConverters.asJava(legalTurnPaths)) {
var pathJava = toJavaIntegerList(pathScala);

// Apply sequence of Move values using makeMove_Move to get final turn state
var currentState = initialState;
for (var moveInt : pathJava) {
currentState = applyMove(currentState, moveInt);
}

// Score final state from initial mover's perspective
var score = evaluator.evaluate(currentState, activeColor);

if (score > bestScore || bestPath == null) {
for (var turn : turns) {
var score = evaluator.evaluate(turn.finalState(), activeColor);
if (bestTurn == null || score > bestScore) {
bestScore = score;
bestPath = pathJava;
bestTurn = turn;
}
}

if (bestPath == null || bestPath.isEmpty()) {
return Collections.emptyList();
}

var moveNotations = new ArrayList<String>();
for (var moveInt : bestPath) {
moveNotations.add(moveToNotation(moveInt));
}

logger.log(Level.DEBUG, "Chosen turn path: {0} with score {1}", moveNotations, bestScore);
return moveNotations;
}

private static GameState applyMove(GameState state, int moveInt) {
try {
return (GameState) MAKE_MOVE_MH.invokeExact(state, moveInt);
} catch (Throwable e) {
throw new IllegalStateException("Failed to apply move via engine: " + moveInt, e);
}
}

/**
* Converts a packed Move int to long algebraic notation (e.g. "e2e4", "e7e8q").
*
* <p>Move layout (from Move.scala):
* <ul>
* <li>Bits 0-5: destination square (to)</li>
* <li>Bits 6-11: source square (from)</li>
* <li>Bits 12-15: move flags</li>
* </ul>
*/
static String moveToNotation(int move) {
var to = move & 0x3f;
var from = (move >>> 6) & 0x3f;
var flags = (move >>> 12) & 0x0f;

var fromFile = (char) ('a' + (from % 8));
var fromRank = (from / 8) + 1;
var toFile = (char) ('a' + (to % 8));
var toRank = (to / 8) + 1;

// Promotion: flags bit 3 set (flags >= 8)
var promStr = "";
if ((flags & 8) != 0) {
promStr = switch (flags & 3) {
case 0 -> "n"; // KnightPromotion(8) or KnightPromoCapture(12)
case 1 -> "b"; // BishopPromotion(9) or BishopPromoCapture(13)
case 2 -> "r"; // RookPromotion(10) or RookPromoCapture(14)
case 3 -> "q"; // QueenPromotion(11) or QueenPromoCapture(15)
default -> "";
};
}

return "" + fromFile + fromRank + toFile + toRank + promStr;
}

private static java.util.List<Integer> toJavaIntegerList(List<Object> scalaList) {
var result = new ArrayList<Integer>();
for (var item : scala.jdk.javaapi.CollectionConverters.asJava(scalaList)) {
if (item instanceof Integer intValue) {
result.add(intValue);
} else if (item instanceof Number number) {
result.add(number.intValue());
}
}
return result;
logger.log(Level.DEBUG, "Chosen turn path: {0} with score {1}", bestTurn.uci(), bestScore);
return bestTurn.uci();
}
}
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