Implement the 'go mate x' uci command (#1076)

Bench: 3204302

Author: Saphereye

src/search.rs

@@ -234,6 +234,14 @@ pub fn start(td: &mut ThreadData, report: Report, thread_count: usize) {
             break;
         }
 
+        if td.id == 0
+            && let Limits::Mate(moves) = td.time_manager.limits()
+            && Score::MATE - td.root_moves[0].score.abs() <= moves as i32 * 2
+        {
+            td.shared.status.set(Status::STOPPED);
+            break;
+        }
+
         let multiplier = || {
             let nodes = {
                 let fraction = td.root_moves[0].nodes as f32 / td.nodes() as f32;

src/time.rs

@@ -8,6 +8,7 @@ pub enum Limits {
     Depth(i32),
     Time(u64),
     Nodes(u64),
+    Mate(u64),
     Fischer(u64, u64),
     Cyclic(u64, u64, u64),
 }
@@ -69,7 +70,7 @@ impl TimeManager {
 
     pub fn soft_limit(&self, td: &ThreadData, multiplier: impl Fn() -> f32) -> bool {
         match self.limits {
-            Limits::Infinite | Limits::Depth(_) => false,
+            Limits::Infinite | Limits::Depth(_) | Limits::Mate(_) => false,
             Limits::Nodes(maximum) => td.shared.nodes.aggregate() >= maximum,
             Limits::Time(maximum) => self.start_time.elapsed() >= Duration::from_millis(maximum),
             _ => self.start_time.elapsed() >= Duration::from_secs_f32(self.soft_bound.as_secs_f32() * multiplier()),
@@ -82,7 +83,7 @@ impl TimeManager {
         }
 
         match self.limits {
-            Limits::Infinite | Limits::Depth(_) => false,
+            Limits::Infinite | Limits::Depth(_) | Limits::Mate(_) => false,
             Limits::Nodes(maximum) => td.shared.nodes.aggregate() > maximum,
             _ => td.nodes() & 2047 == 2047 && self.start_time.elapsed() >= self.hard_bound,
         }

src/uci.rs

@@ -402,6 +402,7 @@ fn parse_limits(color: Color, tokens: &[&str]) -> Limits {
                 "depth" if value > 0 => return Limits::Depth(value as i32),
                 "movetime" if value > 0 => return Limits::Time(value),
                 "nodes" if value > 0 => return Limits::Nodes(value),
+                "mate" if value > 0 => return Limits::Mate(value),
 
                 "wtime" if Color::White == color => main = Some(value),
                 "btime" if Color::Black == color => main = Some(value),