--- a/progs/sudoku.scala	Sat Mar 11 23:10:52 2023 +0000
+++ b/progs/sudoku.scala	Sat Mar 11 23:12:49 2023 +0000
@@ -56,7 +56,7 @@
 def search(game: String): List[String] = {
   if (isDone(game)) List(game)
   else 
-    candidates(game, emptyPosition(game)).
+    candidates(game, emptyPosition(game)).par.
       map(c => search(update(game, empty(game), c))).toList.flatten
 }