fix: allow a little gap when widening windows

This prevents infinite loop when exact score = alpha or beta

1 files changed, 2 insertions, 2 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index 73ddf3c..3caa18b 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -477,14 +477,14 @@ impl Board {
             if search_result.0 <= alpha { // Alpha-cutoff
                 println!("Alpha cutoff {} <= {:?}", search_result.0, (alpha, beta));
                 gradual_widening_counter += 1;
-                beta = alpha;
+                beta = alpha + window_size * 0.1;
                 alpha = search_result.0 - window_size * 2.0f32.powi(gradual_widening_counter);
                 continue;
             }
             if search_result.0 >= beta { // Beta-cutoff
                 println!("Beta cutoff {:?} <= {}", (alpha, beta), search_result.0);
                 gradual_widening_counter += 1;
-                alpha = beta;
+                alpha = beta - window_size * 0.1;
                 beta = search_result.0 + window_size * 2.0f32.powi(gradual_widening_counter);
                 continue;
             }