From 1e81403e62478b0322b850d5ba1cae9e5d6a3e93 Mon Sep 17 00:00:00 2001
From: unknown <p265186@012987.(none)>
Date: Fri, 2 Nov 2012 11:36:28 +0100
Subject: [PATCH] Hopefully fixed difference in A* between windows.Linux.

---
 .../include/PolyVoxCore/AStarPathfinder.h     |  3 +-
 .../include/PolyVoxCore/AStarPathfinder.inl   | 30 ++++++++++---
 tests/TestAStarPathfinder.cpp                 | 42 +++++++++----------
 3 files changed, 48 insertions(+), 27 deletions(-)

diff --git a/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.h b/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.h
index bf983314..83deb6af 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.h
+++ b/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.h
@@ -174,7 +174,8 @@ namespace PolyVox
 		float SixConnectedCost(const Vector3DInt32& a, const Vector3DInt32& b);
 		float EighteenConnectedCost(const Vector3DInt32& a, const Vector3DInt32& b);
 		float TwentySixConnectedCost(const Vector3DInt32& a, const Vector3DInt32& b);
-		float computeH(const Vector3DInt32& a, const Vector3DInt32& b);		
+		float computeH(const Vector3DInt32& a, const Vector3DInt32& b);
+		uint32_t hash(uint32_t a);
 
 		//Node containers
 		AllNodesContainer allNodes;
diff --git a/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.inl b/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.inl
index 03670d02..26c5c398 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.inl
+++ b/library/PolyVoxCore/include/PolyVoxCore/AStarPathfinder.inl
@@ -313,11 +313,17 @@ namespace PolyVox
 		//bias means it is much les likely that two paths are exactly the same
 		//length, and so far fewer nodes must be expanded to find the shortest path.
 		//See http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html#S12
-		polyvox_hash<uint32_t> uint32Hash;
-		uint32_t hashValX = uint32Hash(a.getX());
-		uint32_t hashValY = uint32Hash(a.getY());
-		uint32_t hashValZ = uint32Hash(a.getZ());
-		uint32_t hashVal = hashValX ^ hashValY ^ hashValZ;
+
+		//Note that if the hash is zero we can have differences between the Linux vs. Windows
+		//(or perhaps GCC vs. VS) versions of the code. This is probably because of the way
+		//sorting inside the std::set works (i.e. one system swaps values which are identical
+		//while the other one doesn't - both approaches are valid). For the same reason we want
+		//to make sure that position (x,y,z) has a differnt hash from e.g. position (x,z,y).
+		uint32_t aX = (a.getX() << 16) & 0x00FF0000;
+		uint32_t aY = (a.getY() <<  8) & 0x0000FF00;
+		uint32_t aZ = (a.getZ()      ) & 0x000000FF;
+		uint32_t hashVal = hash(aX | aY | aZ);
+
 		//Stop hashVal going over 65535, and divide by 1000000 to make sure it is small.
 		hashVal &= 0x0000FFFF;
 		float fHash = hashVal / 1000000.0f;
@@ -326,4 +332,18 @@ namespace PolyVox
 		hVal += fHash;
 		return hVal;
 	}
+
+	// Robert Jenkins' 32 bit integer hash function
+	// http://www.concentric.net/~ttwang/tech/inthash.htm
+	template<typename VolumeType>
+	uint32_t AStarPathfinder<VolumeType>::hash( uint32_t a)
+	{
+		a = (a+0x7ed55d16) + (a<<12);
+		a = (a^0xc761c23c) ^ (a>>19);
+		a = (a+0x165667b1) + (a<<5);
+		a = (a+0xd3a2646c) ^ (a<<9);
+		a = (a+0xfd7046c5) + (a<<3);
+		a = (a^0xb55a4f09) ^ (a>>16);
+		return a;
+	}
 }
diff --git a/tests/TestAStarPathfinder.cpp b/tests/TestAStarPathfinder.cpp
index 9493beb5..e8d0170c 100644
--- a/tests/TestAStarPathfinder.cpp
+++ b/tests/TestAStarPathfinder.cpp
@@ -59,27 +59,27 @@ void TestAStarPathfinder::testExecute()
 	{
 		Vector3DInt32(0,0,0),
 		Vector3DInt32(1,1,1),
-		Vector3DInt32(1,2,1),
-		Vector3DInt32(1,3,1),
-		Vector3DInt32(1,4,1),
-		Vector3DInt32(1,5,1),
-		Vector3DInt32(1,6,1),
-		Vector3DInt32(1,7,1),
-		Vector3DInt32(1,8,1),
-		Vector3DInt32(2,9,2),
-		Vector3DInt32(3,10,3),
-		Vector3DInt32(3,11,4),
-		Vector3DInt32(4,12,5),
-		Vector3DInt32(5,12,5),
-		Vector3DInt32(6,13,6),
-		Vector3DInt32(7,13,7),
-		Vector3DInt32(8,13,8),
-		Vector3DInt32(9,13,9),
-		Vector3DInt32(10,13,10),
-		Vector3DInt32(11,13,11),
-		Vector3DInt32(12,13,12),
-		Vector3DInt32(13,13,13),
-		Vector3DInt32(14,14,14),
+		Vector3DInt32(2,1,2),
+		Vector3DInt32(3,1,3),
+		Vector3DInt32(3,1,4),
+		Vector3DInt32(3,1,5),
+		Vector3DInt32(3,1,6),
+		Vector3DInt32(3,1,7),
+		Vector3DInt32(4,2,8),
+		Vector3DInt32(5,3,9),
+		Vector3DInt32(5,3,10),
+		Vector3DInt32(5,3,11),
+		Vector3DInt32(6,4,12),
+		Vector3DInt32(7,5,13),
+		Vector3DInt32(8,6,13),
+		Vector3DInt32(9,7,13),
+		Vector3DInt32(9,8,13),
+		Vector3DInt32(10,9,13),
+		Vector3DInt32(11,10,14),
+		Vector3DInt32(12,11,15),
+		Vector3DInt32(13,12,15),
+		Vector3DInt32(14,13,15),
+		Vector3DInt32(14,14,15),
 		Vector3DInt32(15,15,15)
 	};