Merge pull request #623 from lenguyenthanh/optimize-attacks-initializ…

…e-with-inlines

Use static annotation to optimize Bitboard Magic and Attacks

bench/src/main/scala/benchmarks/PerftBench.scala

@@ -82,16 +82,9 @@ class PerftBench:
     perfts.take(games).map(_.withLimit(nodes))
 
   private def bench(perfts: List[Perft], variant: Variant)(bh: Blackhole) =
-    val x = perfts.map:
+    var i = 0
+    while i < perfts.size do
+      val game = perfts(i)
       Blackhole.consumeCPU(Work)
-      _.calculate(variant)
-    bh.consume(x)
-    x
-
-  extension (perft: Perft)
-    def bench(variant: Variant): List[Result] =
-      var situation = Fen.read(variant, perft.epd).get
-      perft.cases.map: c =>
-        import Perft.*
-        Blackhole.consumeCPU(Work)
-        Result(c.depth, situation.perft(c.depth), c.result)
+      bh.consume(game.calculate(variant))
+      i += 1

core/src/main/scala/Square.scala

@@ -8,7 +8,7 @@ import scala.annotation.targetName
 opaque type Square = Int
 object Square:
   extension (s: Square)
-    def value: Int = s
+    inline def value: Int = s
 
     inline def down: Option[Square]      = Square.at(file.value, rank.value - 1)
     inline def left: Option[Square]      = Square.at(file.value - 1, rank.value)

core/src/main/scala/bitboard/Attacks.scala

@@ -1,26 +1,45 @@
 package chess
 package bitboard
 
+import scala.annotation.static
+
+class Attacks
 object Attacks:
+  @static
   private val all = -1L
 
-  private[bitboard] val RANKS   = Array.fill(8)(0L)
-  private[bitboard] val FILES   = Array.fill(8)(0L)
+  @static
+  private[bitboard] val RANKS = Array.fill(8)(0L)
+  @static
+  private[bitboard] val FILES = Array.fill(8)(0L)
+  @static
   private[bitboard] val BETWEEN = Array.ofDim[Long](64, 64)
-  private[bitboard] val RAYS    = Array.ofDim[Long](64, 64)
+  @static
+  private[bitboard] val RAYS = Array.ofDim[Long](64, 64)
 
   // Large overlapping attack table indexed using magic multiplication.
-  private[bitboard] val ATTACKS            = Array.fill(88772)(0L)
-  private[bitboard] val KNIGHT_ATTACKS     = Array.fill(64)(0L)
-  private[bitboard] val KING_ATTACKS       = Array.fill(64)(0L)
+  @static
+  private[bitboard] val ATTACKS = Array.fill(88772)(0L)
+  @static
+  private[bitboard] val KNIGHT_ATTACKS = Array.fill(64)(0L)
+  @static
+  private[bitboard] val KING_ATTACKS = Array.fill(64)(0L)
+  @static
   private[bitboard] val WHITE_PAWN_ATTACKS = Array.fill(64)(0L)
+  @static
   private[bitboard] val BLACK_PAWN_ATTACKS = Array.fill(64)(0L)
 
-  private val KNIGHT_DELTAS     = Array[Int](17, 15, 10, 6, -17, -15, -10, -6)
-  private val BISHOP_DELTAS     = Array[Int](7, -7, 9, -9)
-  private val ROOK_DELTAS       = Array[Int](1, -1, 8, -8)
-  private val KING_DELTAS       = Array[Int](1, 7, 8, 9, -1, -7, -8, -9)
+  @static
+  private val KNIGHT_DELTAS = Array[Int](17, 15, 10, 6, -17, -15, -10, -6)
+  @static
+  private val BISHOP_DELTAS = Array[Int](7, -7, 9, -9)
+  @static
+  private val ROOK_DELTAS = Array[Int](1, -1, 8, -8)
+  @static
+  private val KING_DELTAS = Array[Int](1, 7, 8, 9, -1, -7, -8, -9)
+  @static
   private val WHITE_PAWN_DELTAS = Array[Int](7, 9)
+  @static
   private val BLACK_PAWN_DELTAS = Array[Int](-7, -9)
 
   /** Slow attack set generation. Used only to bootstrap the attack tables.

core/src/main/scala/bitboard/Magic.scala

@@ -1,11 +1,14 @@
 package chess
 package bitboard
 
-case class Magic(mask: Long, factor: Long, offset: Int):
+import scala.annotation.static
+
+class Magic(val mask: Long, val factor: Long, val offset: Int):
   def bitshopIndex(occupied: Long): Int = (factor * (occupied & mask) >>> (64 - 9)).toInt + offset
   def rookIndex(occupied: Long): Int    = (factor * (occupied & mask) >>> (64 - 12)).toInt + offset
 
 object Magic:
+  @static
   private[bitboard] val ROOK = Array[Magic](
     Magic(0x000101010101017eL, 0x00280077ffebfffeL, 26304),
     Magic(0x000202020202027cL, 0x2004010201097fffL, 35520),
@@ -73,6 +76,7 @@ object Magic:
     Magic(0x7e80808080808000L, 0x0001ffff9dffa333L, 14826)
   )
 
+  @static
   private[bitboard] val BISHOP = Array[Magic](
     Magic(0x0040201008040200L, 0x007fbfbfbfbfbfffL, 5378),
     Magic(0x0000402010080400L, 0x0000a060401007fcL, 4093),