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Copy pathHalfPrecision.cs
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117 lines (95 loc) · 3.13 KB
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/*
* Copyright (c) 2018 Stanislav Denisov
*
* 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.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace NetStack.Quantization {
public static class HalfPrecision {
[StructLayout(LayoutKind.Explicit)]
private struct Values {
[FieldOffset(0)]
public float f;
[FieldOffset(0)]
public int i;
[FieldOffset(0)]
public uint u;
}
[MethodImpl(256)]
public static ushort Quantize(float value) {
var values = new Values {
f = value
};
return Quantize(values.i);
}
public static ushort Quantize(int value) {
int s = (value >> 16) & 0x00008000;
int e = ((value >> 23) & 0X000000FF) - (127 - 15);
int m = value & 0X007FFFFF;
if (e <= 0) {
if (e < -10)
return (ushort)s;
m = m | 0x00800000;
int t = 14 - e;
int a = (1 << (t - 1)) - 1;
int b = (m >> t) & 1;
m = (m + a + b) >> t;
return (ushort)(s | m);
}
if (e == 0XFF - (127 - 15)) {
if (m == 0)
return (ushort)(s | 0X7C00);
m >>= 13;
return (ushort)(s | 0X7C00 | m | ((m == 0) ? 1 : 0));
}
m = m + 0X00000FFF + ((m >> 13) & 1);
if ((m & 0x00800000) != 0) {
m = 0;
e++;
}
if (e > 30)
return (ushort)(s | 0X7C00);
return (ushort)(s | (e << 10) | (m >> 13));
}
public static float Dequantize(ushort value) {
uint result;
uint mantissa = (uint)(value & 1023);
uint exponent = 0XFFFFFFF2;
if ((value & -33792) == 0) {
if (mantissa != 0) {
while ((mantissa & 1024) == 0) {
exponent--;
mantissa = mantissa << 1;
}
mantissa &= 0XFFFFFBFF;
result = ((uint)((((uint)value & 0x8000) << 16) | ((exponent + 127) << 23))) | (mantissa << 13);
} else {
result = (uint)((value & 0x8000) << 16);
}
} else {
result = ((((uint)value & 0x8000) << 16) | ((((((uint)value >> 10) & 0X1F) - 15) + 127) << 23)) | (mantissa << 13);
}
var values = new Values {
u = result
};
return values.f;
}
}
}