From 699ad2f27ae99bb17c6703689f874160ab0e1f18 Mon Sep 17 00:00:00 2001
From: amanjpro <amanjpro@gmail.com>
Date: Wed, 3 Mar 2021 19:53:10 -0500
Subject: [PATCH] Tweak pawn structure and king safety rewards

---
 evaluation/evaluation.go      | 42 ++++++++++++++++++++++++++---------
 evaluation/evaluation_test.go | 30 ++++++++++---------------
 2 files changed, 44 insertions(+), 28 deletions(-)

diff --git a/evaluation/evaluation.go b/evaluation/evaluation.go
index 265224e1..e5e8996b 100644
--- a/evaluation/evaluation.go
+++ b/evaluation/evaluation.go
@@ -625,18 +625,29 @@ func Evaluate(position *Position) int32 {
 			}
 			if blackPawnsPerFile[f] == 0 { // no pawn here
 				if whitePawnsPerFile[f] == 0 { // open file!!
-					blackKingSafetyCentiPawns -= 90
+					blackKingSafetyCentiPawns -= 60
 				} else {
-					blackKingSafetyCentiPawns -= 70
+					blackKingSafetyCentiPawns -= 50
 				}
 			} else {
-				blackKingSafetyCentiPawns -= 6 * (int32(Rank8 - blackLeastAdvancedPawnsPerFile[f]))
+				if blackLeastAdvancedPawnsPerFile[f] == Rank5 {
+					blackKingSafetyCentiPawns -= 25
+				} else if blackLeastAdvancedPawnsPerFile[f] <= Rank4 {
+					blackKingSafetyCentiPawns -= 35 + 8 - int32(blackLeastAdvancedPawnsPerFile[f])
+				}
 			}
 
 			if whitePawnsPerFile[f] != 0 {
-				blackKingSafetyCentiPawns -= 5 * int32(whiteMostAdvancedPawnsPerFile[f])
+				if whiteMostAdvancedPawnsPerFile[f] >= Rank5 {
+					blackKingSafetyCentiPawns -= 25
+				}
 			} else {
-				blackKingSafetyCentiPawns -= 60 // black can pile up
+				wfile := int8(whiteKingSquare.File())
+				if File(wfile-1) != file &&
+					File(wfile) != file &&
+					File(wfile)+1 != file {
+					blackKingSafetyCentiPawns -= 40 // white can pile up
+				}
 			}
 		}
 	}
@@ -670,18 +681,29 @@ func Evaluate(position *Position) int32 {
 			}
 			if whitePawnsPerFile[f] == 0 { // no pawn here
 				if blackPawnsPerFile[f] == 0 { // open file!!
-					whiteKingSafetyCentiPawns -= 90
+					whiteKingSafetyCentiPawns -= 60
 				} else {
-					whiteKingSafetyCentiPawns -= 70
+					whiteKingSafetyCentiPawns -= 50
 				}
 			} else {
-				whiteKingSafetyCentiPawns -= 6 * int32(whiteLeastAdvancedPawnsPerFile[f])
+				if whiteLeastAdvancedPawnsPerFile[f] == Rank4 {
+					whiteKingSafetyCentiPawns -= 25
+				} else if whiteLeastAdvancedPawnsPerFile[f] >= Rank4 {
+					whiteKingSafetyCentiPawns -= 35 + int32(whiteLeastAdvancedPawnsPerFile[f])
+				}
 			}
 
 			if blackPawnsPerFile[f] != 0 {
-				whiteKingSafetyCentiPawns -= 5 * (int32(Rank8 - blackMostAdvancedPawnsPerFile[f]))
+				if blackMostAdvancedPawnsPerFile[f] <= Rank4 {
+					whiteKingSafetyCentiPawns -= 25
+				}
 			} else {
-				whiteKingSafetyCentiPawns -= 60 // black can pile up
+				bfile := int8(blackKingSquare.File())
+				if File(bfile-1) != file &&
+					File(bfile) != file &&
+					File(bfile)+1 != file {
+					whiteKingSafetyCentiPawns -= 40 // black can pile up
+				}
 			}
 		}
 	}
diff --git a/evaluation/evaluation_test.go b/evaluation/evaluation_test.go
index 601a54ca..4b5a9654 100644
--- a/evaluation/evaluation_test.go
+++ b/evaluation/evaluation_test.go
@@ -99,10 +99,9 @@ func TestRookStructureEval(t *testing.T) {
 	game := FromFen(fen, true)
 
 	actual := Evaluate(game.Position())
-	expected := int32(39)
 
-	if actual != expected {
-		err := fmt.Sprintf("Semi-open file - White:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual <= 0 {
+		err := fmt.Sprintf("Semi-open file - White:\nExpected: positive \nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 
@@ -110,10 +109,9 @@ func TestRookStructureEval(t *testing.T) {
 	game = FromFen(fen, true)
 
 	actual = Evaluate(game.Position())
-	expected = int32(39)
 
-	if actual != expected {
-		err := fmt.Sprintf("Semi-open file - Black:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual <= 0 {
+		err := fmt.Sprintf("Semi-open file - Black:\nExpected: positive \nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 }
@@ -124,10 +122,9 @@ func TestKingSafetyEval(t *testing.T) {
 	game := FromFen(fen, true)
 
 	actual := Evaluate(game.Position())
-	expected := int32(-4)
 
-	if actual != expected {
-		err := fmt.Sprintf("Advanced Own Pawn - White:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual >= 0 {
+		err := fmt.Sprintf("Advanced Own Pawn - White:\nExpected: negative \nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 
@@ -136,10 +133,9 @@ func TestKingSafetyEval(t *testing.T) {
 	game = FromFen(fen, true)
 
 	actual = Evaluate(game.Position())
-	expected = int32(-4)
 
-	if actual != expected {
-		err := fmt.Sprintf("Advanced Own Pawn - Black:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual >= 0 {
+		err := fmt.Sprintf("Advanced Own Pawn - Black:\nExpected: negative \nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 
@@ -148,10 +144,9 @@ func TestKingSafetyEval(t *testing.T) {
 	game = FromFen(fen, true)
 
 	actual = Evaluate(game.Position())
-	expected = int32(-33)
 
-	if actual != expected {
-		err := fmt.Sprintf("Missing Own Pawn -open file - Black:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual >= 0 {
+		err := fmt.Sprintf("Missing Own Pawn -open file - White:\nExpected: negative\nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 	fen = "krq5/1pp3pp/8/8/8/8/PPP4P/KRQ5 b - - 0 1"
@@ -159,10 +154,9 @@ func TestKingSafetyEval(t *testing.T) {
 	game = FromFen(fen, true)
 
 	actual = Evaluate(game.Position())
-	expected = int32(-33)
 
-	if actual != expected {
-		err := fmt.Sprintf("Missing Own Pawn -open file - Black:\nExpected: %d\nGot: %d\n", expected, actual)
+	if actual >= 0 {
+		err := fmt.Sprintf("Missing Own Pawn -open file - Black:\nExpected: negative\nGot: %d\n", actual)
 		t.Errorf(err)
 	}
 }