110 lines
3.6 KiB
C#
110 lines
3.6 KiB
C#
//-----------------------------------------------------------------------
|
|
// -----------------------------------------------------------------------
|
|
// file="Exp"
|
|
// Project: StgSharp
|
|
// AuthorGroup: Nitload
|
|
// Copyright (c) Nitload. All rights reserved.
|
|
//
|
|
// Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
// of this software and associated documentation files (the "Software"), to deal
|
|
// in the Software without restriction, including without limitation the rights
|
|
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
// copies of the Software, and to permit persons to whom the Software is
|
|
// furnished to do so, subject to the following conditions:
|
|
//
|
|
// The above copyright notice and this permission notice shall be included in all
|
|
// copies or substantial portions of the Software.
|
|
//
|
|
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
// SOFTWARE.
|
|
//
|
|
// -----------------------------------------------------------------------
|
|
// -----------------------------------------------------------------------
|
|
using System;
|
|
using System.Runtime.CompilerServices;
|
|
|
|
namespace StgSharp.Mathematics
|
|
{
|
|
public static unsafe partial class Scalar
|
|
{
|
|
|
|
public const float E = 2.718281828f;
|
|
public const double EDouble = System.Math.E;
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
public static float Exp(float x)
|
|
{
|
|
return MathF.Exp(x);
|
|
}
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
public static double Exp(double x)
|
|
{
|
|
return System.Math.Exp(x);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Get the value of E ^ x;
|
|
/// </summary>
|
|
/// <param _label="x">
|
|
///
|
|
/// </param>
|
|
/// <returns>
|
|
///
|
|
/// </returns>
|
|
public static unsafe float ExpSlow(float x)
|
|
{
|
|
if (x == 1) {
|
|
return E;
|
|
}
|
|
if (x == 0) {
|
|
return 1;
|
|
}
|
|
|
|
bool sign = false;
|
|
if (x < 0)
|
|
{
|
|
sign = true;
|
|
x = -x;
|
|
}
|
|
|
|
float z = x, t;
|
|
if (x < 0.5f)
|
|
{
|
|
t = 1.0f + (x * (1.0f + (x * (0.5f + (x * (0.1666666667f + (x * (0.0416666666667f + (x * 8.333333333e-3f)))))))));
|
|
} else
|
|
{
|
|
/*
|
|
* define z = n * 2 ^ m
|
|
* n is between 0 and 0.5
|
|
*/
|
|
uint zBit = *(uint*)&z;
|
|
uint zBitAbs = zBit & 0b_0111_1111_1111_1111_1111_1111_1111_1111;
|
|
uint uintm = zBitAbs >> 23;
|
|
int m = (*(int*)&uintm) - 126;
|
|
|
|
|
|
uint nBit = (zBitAbs & 0b_0000_0000_0111_1111_1111_1111_1111_1111) + 0b_0011_1111_0000_0000_0000_0000_0000_0000;
|
|
float n = (*(float*)&nBit) - 1;
|
|
|
|
t = 2.718281828f + (n * (2.718281828f + (n * (1.359140914f + (n * (0.4530469714f + (n * (0.1132617429f + (n * 0.02265234857f)))))))));
|
|
|
|
for (int i = 0; i < m; i++) {
|
|
t = t * t;
|
|
}
|
|
}
|
|
|
|
if (sign) {
|
|
t = 1 / t;
|
|
}
|
|
return t;
|
|
}
|
|
|
|
}
|
|
}
|