Changed data structure of 'neis' from List<byte> to byte[] for optimized memory usage and improved access speed in `DtLayerMonotoneRegion`

CHANGELOG.md

@@ -13,7 +13,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Nothing
 
 ### Changed
-- Nothing
+- Changed data structure of 'neis' from List<byte> to byte[] for optimized memory usage and improved access speed in `DtLayerMonotoneRegion`
 
 ### Removed
 - Nothing

src/DotRecast.Core/Numerics/RcVec.cs

@@ -135,6 +135,14 @@ namespace DotRecast.Core.Numerics
             @out[n + 1] = @in[m + 1];
             @out[n + 2] = @in[m + 2];
         }
+        
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Copy(Span<float> @out, int n, Span<float> @in, int m)
+        {
+            @out[n + 0] = @in[m + 0];
+            @out[n + 1] = @in[m + 1];
+            @out[n + 2] = @in[m + 2];
+        }
 
         /// Returns the distance between two points.
         /// @param[in] v1 A point. [(x, y, z)]

src/DotRecast.Detour.TileCache/DtLayerMonotoneRegion.cs

@@ -7,7 +7,8 @@ namespace DotRecast.Detour.TileCache
         public const int DT_LAYER_MAX_NEIS = 16;
 
         public int area;
-        public List<byte> neis = new List<byte>(DT_LAYER_MAX_NEIS);
+        public byte[] neis = new byte[DT_LAYER_MAX_NEIS];
+        public byte nneis;
         public byte regId;
         public byte areaId;
     };

src/DotRecast.Detour.TileCache/DtTileCacheBuilder.cs

@@ -181,8 +181,8 @@ namespace DotRecast.Detour.TileCache
                         byte rai = layer.regs[ymi];
                         if (rai != 0xff && rai != ri)
                         {
-                            AddUniqueLast(regs[ri].neis, rai);
+                            AddUniqueLast(regs[ri].neis, ref regs[ri].nneis, rai);
-                            AddUniqueLast(regs[rai].neis, ri);
+                            AddUniqueLast(regs[rai].neis, ref regs[rai].nneis, ri);
                         }
                     }
                 }
@@ -197,8 +197,9 @@ namespace DotRecast.Detour.TileCache
 
                 int merge = -1;
                 int mergea = 0;
-                foreach (int nei in reg.neis)
+                for (int j = 0; j < reg.nneis; ++j)
                 {
+                    byte nei = reg.neis[j];
                     DtLayerMonotoneRegion regn = regs[nei];
                     if (reg.regId == regn.regId)
                         continue;
@@ -246,12 +247,13 @@ namespace DotRecast.Detour.TileCache
             }
         }
 
-        public static void AddUniqueLast(List<byte> a, byte v)
+        public static void AddUniqueLast(byte[] a, ref byte an, byte v)
         {
-            int n = a.Count;
+            int n = an;
             if (n > 0 && a[n - 1] == v)
                 return;
-            a.Add(v);
+            a[an] = v;
+            an++;
         }
 
         public static bool IsConnected(DtTileCacheLayer layer, int ia, int ib, int walkableClimb)
@@ -271,9 +273,11 @@ namespace DotRecast.Detour.TileCache
                 DtLayerMonotoneRegion reg = regs[i];
                 if (reg.regId != oldRegId)
                     continue;
-                foreach (int nei in reg.neis)
+
+                int nnei = reg.nneis;
+                for (int j = 0; j < nnei ; ++j)
                 {
-                    if (regs[nei].regId == newRegId)
+                    if (regs[reg.neis[j]].regId == newRegId)
                         count++;
                 }
             }

src/DotRecast.Recast/RcLayers.cs

@@ -32,7 +32,6 @@ namespace DotRecast.Recast
         const int RC_MAX_LAYERS = RcRecast.RC_NOT_CONNECTED;
         const int RC_MAX_NEIS = 16;
 
-
         private static void AddUnique(List<int> a, int v)
         {
             if (!a.Contains(v))

src/DotRecast.Recast/RcRasterizations.cs

@@ -209,7 +209,7 @@ namespace DotRecast.Recast
         /// @param[out]	outVerts2Count	The number of resulting polygon 2 vertices
         /// @param[in]	axisOffset		THe offset along the specified axis
         /// @param[in]	axis			The separating axis
-        private static void DividePoly(float[] inVerts, int inVertsOffset, int inVertsCount,
+        private static void DividePoly(Span<float> inVerts, int inVertsOffset, int inVertsCount,
             int outVerts1, out int outVerts1Count,
             int outVerts2, out int outVerts2Count,
             float axisOffset, int axis)
@@ -322,7 +322,7 @@ namespace DotRecast.Recast
             z1 = Math.Clamp(z1, 0, h - 1);
 
             // Clip the triangle into all grid cells it touches.
-            float[] buf = new float[7 * 3 * 4];
+            Span<float> buf = stackalloc float[7 * 3 * 4];
             int @in = 0;
             int inRow = 7 * 3;
             int p1 = inRow + 7 * 3;

src/DotRecast.Recast/RcRegions.cs

@@ -1665,8 +1665,8 @@ namespace DotRecast.Recast
 
             ctx.StartTimer(RcTimerLabel.RC_TIMER_BUILD_REGIONS_WATERSHED);
 
-            int LOG_NB_STACKS = 3;
+            const int LOG_NB_STACKS = 3;
-            int NB_STACKS = 1 << LOG_NB_STACKS;
+            const int NB_STACKS = 1 << LOG_NB_STACKS;
             List<List<RcLevelStackEntry>> lvlStacks = new List<List<RcLevelStackEntry>>();
             for (int i = 0; i < NB_STACKS; ++i)
             {
@@ -1756,7 +1756,7 @@ namespace DotRecast.Recast
             ExpandRegions(expandIters * 8, 0, chf, srcReg, srcDist, stack, true);
 
             ctx.StopTimer(RcTimerLabel.RC_TIMER_BUILD_REGIONS_WATERSHED);
-
+            
             ctx.StartTimer(RcTimerLabel.RC_TIMER_BUILD_REGIONS_FILTER);
 
             // Merge regions and filter out small regions.