Remove IID

src/search/pvs.rs

@@ -150,7 +150,6 @@ fn pvs<const ROOT: bool, const MAIN_THREAD: bool, const ALLOW_NMR: bool>(
     // Position and node type considerations.
     let is_check = position.is_check();
     let may_be_zug = may_be_zugzwang(position);
-    let is_pv = alpha != beta - 1;
 
     // Null move pruning: if we "pass" our turn and still get a beta cutoff,
     // this position is far too good to be true.
@@ -184,23 +183,6 @@ fn pvs<const ROOT: bool, const MAIN_THREAD: bool, const ALLOW_NMR: bool>(
         }
     }
 
-    // Internal iterative deepening: get a hash move from a reduced search.
-    // This is useless in most cases, but can be very useful in some
-    // where standard move ordering fails to be decent.
-    if is_pv && !is_check && !ROOT && depth >= 4 && table.get_hash_move(position).is_none() {
-        let (_, iid_count) = pvs::<true, MAIN_THREAD, false>(
-            position,
-            depth.saturating_sub(2),
-            alpha,
-            beta,
-            table.clone(),
-            constraint,
-            history,
-            ply,
-        );
-        count += iid_count;
-    }
-
     // Prepare move generation and sorting. This is lazy and works in stages.
     let mut picker =
         MovePicker::<false>::new(position, table.clone(), ply, ROOT && !MAIN_THREAD).peekable();