fix mate problem

src/engine.rs

@@ -313,7 +313,7 @@ impl Engine {
                     let infostring = format!("info depth {} score mate {} time {} nodes {} nps {} hashfull {} pv{}", depth, turns, elapsed.as_millis(), nodes, nps, hashfull, pv);
                     println!("{}", infostring);
                     info!("{}", infostring);
-                    if si.depth.is_none() {
+                    if si.depth.is_none() && plies.abs() * 2 <= depth {
                         break;
                     }
                 }