Merge pull request #5767 from pchote/isqrt

Add Exts.ISqrt to avoid fp sqrt calculations.

OpenRA.Game/CVec.cs

@@ -42,7 +42,7 @@ namespace OpenRA
 		public CVec Sign() { return new CVec(Math.Sign(X), Math.Sign(Y)); }
 		public CVec Abs() { return new CVec(Math.Abs(X), Math.Abs(Y)); }
 		public int LengthSquared { get { return X * X + Y * Y; } }
-		public int Length { get { return (int)Math.Sqrt(LengthSquared); } }
+		public int Length { get { return Exts.ISqrt(LengthSquared); } }
 
 		public CVec Clamp(Rectangle r)
 		{

OpenRA.Game/Exts.cs

@@ -202,6 +202,91 @@ namespace OpenRA
 
 		public static Size NextPowerOf2(this Size s) { return new Size(NextPowerOf2(s.Width), NextPowerOf2(s.Height)); }
 
+		public enum ISqrtRoundMode { Floor, Nearest, Ceiling }
+		public static int ISqrt(int number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
+		{
+			if (number < 0)
+				throw new InvalidOperationException("Attempted to calculate the square root of a negative integer: {0}".F(number));
+
+			return (int)ISqrt((uint)number, round);
+		}
+
+		public static uint ISqrt(uint number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
+		{
+			var divisor = 1U << 30;
+
+			var root = 0U;
+			var remainder = number;
+
+			// Find the highest term in the divisor
+			while (divisor > number)
+				divisor >>= 2;
+
+			// Evaluate the root, two bits at a time
+			while (divisor != 0)
+			{
+				if (root + divisor <= remainder)
+				{
+					remainder -= root + divisor;
+					root += 2 * divisor;
+				}
+
+				root >>= 1;
+				divisor >>= 2;
+			}
+
+			// Adjust for other rounding modes
+			if (round == ISqrtRoundMode.Nearest && remainder > root)
+				root += 1;
+
+			else if (round == ISqrtRoundMode.Ceiling && root * root < number)
+				root += 1;
+
+			return root;
+		}
+
+		public static long ISqrt(long number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
+		{
+			if (number < 0)
+				throw new InvalidOperationException("Attempted to calculate the square root of a negative integer: {0}".F(number));
+
+			return (long)ISqrt((ulong)number, round);
+		}
+
+		public static ulong ISqrt(ulong number, ISqrtRoundMode round = ISqrtRoundMode.Floor)
+		{
+			var divisor = 1UL << 62;
+
+			var root = 0UL;
+			var remainder = number;
+
+			// Find the highest term in the divisor
+			while (divisor > number)
+				divisor >>= 2;
+
+			// Evaluate the root, two bits at a time
+			while (divisor != 0)
+			{
+				if (root + divisor <= remainder)
+				{
+					remainder -= root + divisor;
+					root += 2 * divisor;
+				}
+
+				root >>= 1;
+				divisor >>= 2;
+			}
+
+			// Adjust for other rounding modes
+			if (round == ISqrtRoundMode.Nearest && remainder > root)
+				root += 1;
+
+			else if (round == ISqrtRoundMode.Ceiling && root * root < number)
+				root += 1;
+
+			return root;
+		}
+
 		public static string JoinWith<T>(this IEnumerable<T> ts, string j)
 		{
 			return string.Join(j, ts);

OpenRA.Game/Graphics/LineRenderer.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -8,6 +8,7 @@
  */
 #endregion
 
+using System;
 using System.Drawing;
 
 namespace OpenRA.Graphics
@@ -98,7 +99,7 @@ namespace OpenRA.Graphics
 			var yc = (r.Bottom + r.Top) / 2;
 			for (var y = r.Top; y <= r.Bottom; y++)
 			{
-				var dx = a * System.Convert.ToSingle(System.Math.Sqrt(1 - (y - yc) * (y - yc) / b / b));
+				var dx = a * (float)(Math.Sqrt(1 - (y - yc) * (y - yc) / b / b));
 				DrawLine(new float2(xc - dx, y), new float2(xc + dx, y), color, color);
 			}
 		}

OpenRA.Game/Map/Map.cs

@@ -712,7 +712,7 @@ namespace OpenRA
 			for (var j = -max; j <= max; j++)
 				for (var i = -max; i <= max; i++)
 					if (max * max >= i * i + j * j)
-						ts [(int)Math.Ceiling(Math.Sqrt(i * i + j * j))].Add(new CVec(i, j));
+						ts [Exts.ISqrt(i * i + j * j, Exts.ISqrtRoundMode.Ceiling)].Add(new CVec(i, j));
 
 			// Sort each integer-distance group by the actual distance
 			foreach (var list in ts)

OpenRA.Game/Primitives/int2.cs

@@ -35,7 +35,7 @@ namespace OpenRA
 		public int2 Sign() { return new int2(Math.Sign(X), Math.Sign(Y)); }
 		public int2 Abs() { return new int2(Math.Abs(X), Math.Abs(Y)); }
 		public int LengthSquared { get { return X * X + Y * Y; } }
-		public int Length { get { return (int)Math.Sqrt(LengthSquared); } }
+		public int Length { get { return Exts.ISqrt(LengthSquared); } }
 		public override int GetHashCode() { return X.GetHashCode() ^ Y.GetHashCode(); }
 
 		public static int2 Max(int2 a, int2 b) { return new int2(Math.Max(a.X, b.X), Math.Max(a.Y, b.Y)); }

OpenRA.Game/WVec.cs

@@ -37,9 +37,9 @@ namespace OpenRA
 
 		public static int Dot(WVec a, WVec b) { return a.X * b.X + a.Y * b.Y + a.Z * b.Z; }
 		public long LengthSquared { get { return (long)X * X + (long)Y * Y + (long)Z * Z; } }
-		public int Length { get { return (int)Math.Sqrt(LengthSquared); } }
+		public int Length { get { return (int)Exts.ISqrt(LengthSquared); } }
 		public long HorizontalLengthSquared { get { return (long)X * X + (long)Y * Y; } }
-		public int HorizontalLength { get { return (int)Math.Sqrt(HorizontalLengthSquared); } }
+		public int HorizontalLength { get { return (int)Exts.ISqrt(HorizontalLengthSquared); } }
 
 		public WVec Rotate(WRot rot)
 		{