adjust threads

src/elo.rs

@@ -156,8 +156,8 @@ impl PlayerArena {
                         (std::thread::available_parallelism()
                             .map(NonZero::get)
                             .expect("unable to get number of threads")
-                            / 3)
-                            * 2,
+                            / 5)
+                            * 3,
                     )
                     .build_global()
                     .unwrap();