From cfea4b23ef73d064001ffa0b17366f13d715ff0a Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Mon, 20 Feb 2023 22:52:50 +0300
Subject: feat: accept and gracefully handle instability
---
src/board/engine.rs | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
(limited to 'src')
diff --git a/src/board/engine.rs b/src/board/engine.rs
index ee5be65..2e22b35 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -566,6 +566,14 @@ impl Board {
let mut gradual_widening_counter = 0;
let mut root_killers: Vec<Move> = Vec::new();
+ // Gracefully handle search instability
+ #[derive(PartialEq)]
+ enum Cutoff {
+ Alpha,
+ Beta,
+ }
+ let mut latest_cutoff = None;
+
while depth <= max_depth {
if print {
@@ -595,6 +603,16 @@ impl Board {
gradual_widening_counter += 1;
beta = alpha + window_size * 0.1;
alpha = search_result.0 - window_size * 2.0f32.powi(gradual_widening_counter);
+ if latest_cutoff == Some(Cutoff::Beta) {
+ println!("Detected search instability! You are probably in Zugzwang. Aborting...");
+ depth += 1;
+ latest_cutoff = None;
+ gradual_widening_counter = 0;
+ alpha = search_result.0 - window_size;
+ beta = search_result.0 + window_size;
+ continue;
+ }
+ latest_cutoff = Some(Cutoff::Alpha);
continue;
}
if search_result.0 >= beta { // Beta-cutoff
@@ -604,11 +622,22 @@ impl Board {
gradual_widening_counter += 1;
alpha = beta - window_size * 0.1;
beta = search_result.0 + window_size * 2.0f32.powi(gradual_widening_counter);
+ if latest_cutoff == Some(Cutoff::Alpha) {
+ println!("Detected search instability! You are probably in Zugzwang. Aborting...");
+ depth += 1;
+ latest_cutoff = None;
+ gradual_widening_counter = 0;
+ alpha = search_result.0 - window_size;
+ beta = search_result.0 + window_size;
+ continue;
+ }
+ latest_cutoff = Some(Cutoff::Beta);
continue;
}
if search_result.1.len() > 0 {
depth += 1;
+ latest_cutoff = None;
gradual_widening_counter = 0;
alpha = search_result.0 - window_size;
beta = search_result.0 + window_size;
--
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