manvscode · April 8, 2019 04:45 · May 4, 2016
diff --git a/FastExp.cs b/FastExp.cs
@@ -0,0 +1,16 @@
+/// <summary>
+/// Fast exponential approximation.
+/// </summary>
+/// <remarks>
+/// Based on "A Fast, Compact Approximation of the Exponential Function" by Nicol N.Schraudolph (1999)
+/// <code>e^x ~ a*x + b
+/// a = 2 ^ (mantissa bits) / ln(2) ~ 12102203
+/// b = (exponent bias) * 2^(mantissa bits) ~ 1065353216</code>
+/// </remarks>
+/// <param name="x">A number specifying a power.</param>
+/// <returns>The number e raised to the power x.</returns>
+public static float FastExp(float x)
+{
+    var temp = (int)(12102203 * x + 1065353216);
+    return BitConverter.ToSingle(BitConverter.GetBytes(temp), 0);
+}