📦 NEW: Policy Temperature Root

src/options.rs

@@ -9,6 +9,7 @@ static HASH_SIZE_MB: AtomicUsize = AtomicUsize::new(16);
 static CPUCT: Lazy<RwLock<f32>> = Lazy::new(|| RwLock::new(1.85));
 static CVISITS_SELECTION: Lazy<RwLock<f32>> = Lazy::new(|| RwLock::new(0.01));
 static POLICY_TEMPERATURE: Lazy<RwLock<f32>> = Lazy::new(|| RwLock::new(1.2));
+static POLICY_TEMPERATURE_ROOT: Lazy<RwLock<f32>> = Lazy::new(|| RwLock::new(3.5));
 
 static CHESS960: AtomicBool = AtomicBool::new(false);
 
@@ -58,6 +59,16 @@ pub fn get_policy_temperature() -> f32 {
     *pt
 }
 
+pub fn set_policy_temperature_root(t: f32) {
+    let mut pt = POLICY_TEMPERATURE_ROOT.write().unwrap();
+    *pt = t;
+}
+
+pub fn get_policy_temperature_root() -> f32 {
+    let pt = POLICY_TEMPERATURE_ROOT.read().unwrap();
+    *pt
+}
+
 pub fn set_chess960(c: bool) {
     CHESS960.store(c, Ordering::Relaxed);
 }

src/search_tree.rs

@@ -7,9 +7,10 @@ use std::sync::atomic::{AtomicI64, AtomicPtr, AtomicU32, AtomicU64, AtomicUsize,
 
 use crate::arena::Error as ArenaError;
 use crate::evaluation::{self, Flag};
-use crate::math;
 use crate::mcts::{eval_in_cp, ThreadData};
-use crate::options::{get_cpuct, get_cvisits_selection, get_policy_temperature};
+use crate::options::{
+    get_cpuct, get_cvisits_selection, get_policy_temperature, get_policy_temperature_root,
+};
 use crate::search::{to_uci, TimeManagement, SCALE};
 use crate::state::State;
 use crate::transposition_table::{LRAllocator, LRTable, TranspositionTable};
@@ -62,10 +63,6 @@ impl SearchNode {
         Self { hots, flag }
     }
 
-    pub fn is_visited(&self) -> bool {
-        self.hots().iter().any(|x| x.visits() > 0)
-    }
-
     pub fn flag(&self) -> Flag {
         self.flag
     }
@@ -86,15 +83,6 @@ impl SearchNode {
         unsafe { &*(self.hots) }
     }
 
-    fn update_policy(&mut self, evals: &[f32]) {
-        let hots = unsafe { &mut *(self.hots.cast_mut()) };
-
-        #[allow(clippy::cast_sign_loss)]
-        for i in 0..hots.len().min(evals.len()) {
-            hots[i].policy = (evals[i].clamp(0., 0.99) * SCALE) as u16;
-        }
-    }
-
     pub fn clear_children_links(&self) {
         let hots = unsafe { &*(self.hots.cast_mut()) };
 
@@ -201,24 +189,12 @@ impl SearchTree {
             &state,
             &tb_hits,
             |sz| root_table.arena().allocator().alloc_slice(sz),
-            1.0,
+            get_policy_temperature_root(),
         )
         .expect("Unable to create root node");
 
         previous_table.lookup_into(&state, &mut root_node);
 
-        if root_node.is_visited() {
-            let mut avg_rewards: Vec<f32> = root_node
-                .hots()
-                .iter()
-                .map(|m| m.average_reward().unwrap_or(-SCALE) / SCALE)
-                .collect();
-
-            math::softmax(&mut avg_rewards, 1.0);
-
-            root_node.update_policy(&avg_rewards);
-        }
-
         Self {
             root_state: state,
             root_node,

src/uci.rs

@@ -5,7 +5,7 @@ use std::thread;
 
 use crate::options::{
     set_chess960, set_cpuct, set_cvisits_selection, set_hash_size_mb, set_num_threads,
-    set_policy_temperature,
+    set_policy_temperature, set_policy_temperature_root,
 };
 use crate::search::Search;
 use crate::search_tree::print_size_list;
@@ -82,6 +82,7 @@ pub fn uci() {
     println!("option name CPuct type string default 1.85");
     println!("option name CVisitsSelection type string default 0.01");
     println!("option name PolicyTemperature type string default 1.2");
+    println!("option name PolicyTemperatureRoot type string default 3.5");
     println!("option name UCI_Chess960 type check default false");
 
     println!("uciok");
@@ -143,6 +144,7 @@ impl UciOption {
             "cpuct" => self.set_option(set_cpuct),
             "cvisitsselection" => self.set_option(set_cvisits_selection),
             "policytemperature" => self.set_option(set_policy_temperature),
+            "policytemperatureroot" => self.set_option(set_policy_temperature_root),
             "uci_chess960" => self.set_option(set_chess960),
             _ => warn!("Badly formatted or unknown option"),
         }