Added AlmostEquals method from Math.NET Iridium

Signed-off-by: Marcus Cuda <marcus@cuda.net>

src/Managed.UnitTests/PrecisionTest.cs

@@ -482,6 +482,16 @@ namespace MathNet.Numerics.UnitTests
             Precision.AlmostEqual(1, 2, 0);
         }
 
+        [Test]
+        public void AlmostEqual()
+        {
+            AssertEx.That(()=>1.0.AlmostEqual(1.0), "1.0 equals 1.0.");
+            AssertEx.That(() => 1.0.AlmostEqual(1.0 + _doublePrecision), "1.0 equals 1.0 + 2^(-53).");
+            AssertEx.That(() => 1.0.AlmostEqual(1.0 + _doublePrecision * 10), "1.0 equals 1.0 + 2^(-52).");
+            AssertEx.That(() => !1.0.AlmostEqual(1.0 + _doublePrecision * 100), "1.0 does not equal 1.0 + 2^(-51).");
+            AssertEx.That(() => !1.0.AlmostEqual(2.0), "1.0 does not equal 2.0");
+        }
+
         [Test]
         public void AlmostEqualWithMaxNumbersBetween()
         {

src/Managed/Precision.cs

@@ -71,6 +71,32 @@ namespace MathNet.Numerics
 
         #endregion
 
+        #region Properties
+        /// <summary>
+        /// Gets the maximum relative precision of a double.
+        /// </summary>
+        /// <value>The maximum relative precision of a double.</value>
+        public static double DoubleMachinePrecision
+        {
+            get
+            {
+                return _doubleMachinePrecision;
+            }
+        }
+
+        /// <summary>
+        /// Gets the maximum relative precision of a single.
+        /// </summary>
+        /// <value>The maximum relative precision of a single.</value>
+        public static double SingleMachinePrecision
+        {
+            get
+            {
+                return _singleMachinePrecision;
+            }
+        }
+        #endregion
+
         #region Fields
 
         /// <summary>
@@ -93,6 +119,9 @@ namespace MathNet.Numerics
         /// </summary>
         private static readonly int _numberOfDecimalPlacesForFloats;
 
+        /// <summary>Value representing 10 * 2^(-52)</summary>
+        private static readonly double _defaultRelativeAccuracy = _doubleMachinePrecision * 10;
+
         #endregion
 
         /// <summary>
@@ -670,6 +699,22 @@ namespace MathNet.Numerics
             return AlmostZero(a, _doubleMachinePrecision);
         }
 
+        /// <summary>
+        /// Checks whether two real numbers are almost equal.
+        /// </summary>
+        /// <param name="a">The first number</param>
+        /// <param name="b">The second number</param>
+        /// <returns>true if the two values differ by no more than 10 * 2^(-52); false otherwise.</returns>
+        public static bool AlmostEqual(this double a, double b)
+        {
+            if ((a == 0 && Math.Abs(b) < _defaultRelativeAccuracy) || (b == 0 && Math.Abs(a) < _defaultRelativeAccuracy))
+            {
+                return true;
+            }
+
+            return Math.Abs(a - b) < _defaultRelativeAccuracy * Math.Max(Math.Abs(a), Math.Abs(b));
+        }
+
         /// <summary>
         /// Compares two doubles and determines if they are equal to within the tolerance or not. Equality comparison is based on the binary representation.
         /// </summary>