Try to match relative magnitude of NNUE eval to classical

The idea is that since we are mixing NNUE and classical evals matching their magnitudes closer allows for better comparisons.

STC https://tests.stockfishchess.org/tests/view/5f35a65411a9b1a1dbf18e2b
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 9840 W: 1150 L: 1027 D: 7663
Ptnml(0-2): 49, 772, 3175, 855, 69

LTC https://tests.stockfishchess.org/tests/view/5f35bcbe11a9b1a1dbf18e47
LLR: 2.93 (-2.94,2.94) {0.25,1.75}
Total: 44424 W: 2492 L: 2294 D: 39638
Ptnml(0-2): 42, 2015, 17915, 2183, 57

also corrects the location to clamp the evaluation (non-function on bench).

closes https://github.com/official-stockfish/Stockfish/pull/3003

bench: 3905447

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 00fd2005ed7445008263db7f71c547c72a3ef997..a453fa0f7f4cd871a821fbe38827695f05bfc694 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -941,11 +941,14 @@ Value Eval::evaluate(const Position& pos) {
   bool classical = !Eval::useNNUE
                 ||  abs(eg_value(pos.psq_score())) >= NNUEThreshold;
   Value v = classical ? Evaluation<NO_TRACE>(pos).value()
-                      : NNUE::evaluate(pos) + Tempo;
+                      : NNUE::evaluate(pos) * 5 / 4 + Tempo;
 
   // Damp down the evaluation linearly when shuffling
   v = v * (100 - pos.rule50_count()) / 100;
 
+  // Guarantee evalution outside of TB range
+  v = Utility::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
+
   return v;
 }
 

diff --git a/src/nnue/evaluate_nnue.cpp b/src/nnue/evaluate_nnue.cpp
index af0894b2f9e6a84cfffcb92aebcc75ccc8285d0c..a6ece8e2427b1fe731e68667dbac1e99720d4e2c 100644 (file)
--- a/src/nnue/evaluate_nnue.cpp
+++ b/src/nnue/evaluate_nnue.cpp
@@ -159,10 +159,7 @@ namespace Eval::NNUE {
 
   // Evaluation function. Perform differential calculation.
   Value evaluate(const Position& pos) {
-    Value v = ComputeScore(pos, false);
-    v = Utility::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
-
-    return v;
+    return ComputeScore(pos, false);
   }
 
   // Evaluation function. Perform full calculation.