From c0107b3c27e9542a3319e9af0396794b7b2df890 Mon Sep 17 00:00:00 2001
From: cj5716 <125858804+cj5716@users.noreply.github.com>
Date: Tue, 6 Feb 2024 16:56:13 +0800
Subject: [PATCH] Remove simple eval

With the recent introduction of the dual NNUE, the
need for simple eval is no longer there.

Passed STC:
https://tests.stockfishchess.org/tests/view/65c1f735c865510db0281652
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 85312 W: 22009 L: 21837 D: 41466
Ptnml(0-2): 334, 10155, 21567, 10205, 395

Passed LTC:
https://tests.stockfishchess.org/tests/view/65c2d64bc865510db0282810
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 49956 W: 12596 L: 12402 D: 24958
Ptnml(0-2): 28, 5553, 13624, 5743, 30

closes https://github.com/official-stockfish/Stockfish/pull/5037

Bench 1213676
---
 src/evaluate.cpp | 33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 45658798..c8656fc2 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -199,33 +199,24 @@ Value Eval::evaluate(const Position& pos, int optimism) {
 
     assert(!pos.checkers());
 
-    int   v;
-    Color stm        = pos.side_to_move();
-    int   shuffling  = pos.rule50_count();
-    int   simpleEval = simple_eval(pos, stm);
+    int  simpleEval = simple_eval(pos, pos.side_to_move());
+    bool smallNet   = std::abs(simpleEval) > 1050;
 
-    bool lazy = std::abs(simpleEval) > 2550;
-    if (lazy)
-        v = simpleEval;
-    else
-    {
-        bool smallNet = std::abs(simpleEval) > 1050;
+    int nnueComplexity;
 
-        int nnueComplexity;
+    Value nnue = smallNet ? NNUE::evaluate<NNUE::Small>(pos, true, &nnueComplexity)
+                          : NNUE::evaluate<NNUE::Big>(pos, true, &nnueComplexity);
 
-        Value nnue = smallNet ? NNUE::evaluate<NNUE::Small>(pos, true, &nnueComplexity)
-                              : NNUE::evaluate<NNUE::Big>(pos, true, &nnueComplexity);
+    // Blend optimism and eval with nnue complexity and material imbalance
+    optimism += optimism * (nnueComplexity + std::abs(simpleEval - nnue)) / 512;
+    nnue -= nnue * (nnueComplexity + std::abs(simpleEval - nnue)) / 32768;
 
-        // Blend optimism and eval with nnue complexity and material imbalance
-        optimism += optimism * (nnueComplexity + std::abs(simpleEval - nnue)) / 512;
-        nnue -= nnue * (nnueComplexity + std::abs(simpleEval - nnue)) / 32768;
-
-        int npm = pos.non_pawn_material() / 64;
-        v       = (nnue * (915 + npm + 9 * pos.count<PAWN>()) + optimism * (154 + npm)) / 1024;
-    }
+    int npm = pos.non_pawn_material() / 64;
+    int v   = (nnue * (915 + npm + 9 * pos.count<PAWN>()) + optimism * (154 + npm)) / 1024;
 
     // Damp down the evaluation linearly when shuffling
-    v = v * (200 - shuffling) / 214;
+    int shuffling = pos.rule50_count();
+    v             = v * (200 - shuffling) / 214;
 
     // Guarantee evaluation does not hit the tablebase range
     v = std::clamp(int(v), VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);