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randomdouble implementation tweaks

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This commit is contained in:
Mark Sturgill 2013-10-14 14:28:48 -07:00
parent 3c1bc12829
commit 710c600b65
1 changed files with 68 additions and 9 deletions
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77
Server/Random.cs
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@ -154,6 +154,15 @@ namespace Server {
} }
} }
private void _GetBytes(byte[] b, int offset, int count) {
CheckSwap(count);
lock (_sync) {
Buffer.BlockCopy(_Working, _Index, b, offset, count);
_Index += count;
}
}
public int Next(int c) { public int Next(int c) {
return (int)(c * NextDouble()); return (int)(c * NextDouble());
} }
@ -180,17 +189,27 @@ namespace Server {
_GetBytes(b); _GetBytes(b);
} }
public double NextDouble() { public unsafe double NextDouble() {
byte[] b = new byte[8]; byte[] b = new byte[8];
_GetBytes(b); if (BitConverter.IsLittleEndian) {
b[7] = 0;
_GetBytes(b, 0, 7);
} else {
b[0] = 0;
_GetBytes(b, 1, 7);
}
ulong r = 0;
fixed(byte* buf = b)
r = *(ulong*)(&buf[0]) >> 3;
/* double: 53 bits of significand precision /* double: 53 bits of significand precision
* ulong.MaxValue >> 11 = 9007199254740991 * ulong.MaxValue >> 11 = 9007199254740991
* 2^53 = 9007199254740992 * 2^53 = 9007199254740992
*/ */
return ((double)(BitConverter.ToUInt64(b, 0) >> 11) / 9007199254740992); return (double)r / 9007199254740992;
} }
} }
@ -252,6 +271,15 @@ namespace Server {
} }
} }
private void _GetBytes(byte[] b, int offset, int count) {
CheckSwap(count);
lock (_sync) {
Buffer.BlockCopy(_Working, _Index, b, offset, count);
_Index += count;
}
}
public int Next(int c) { public int Next(int c) {
return (int)(c * NextDouble()); return (int)(c * NextDouble());
} }
@ -277,16 +305,27 @@ namespace Server {
_GetBytes(b); _GetBytes(b);
} }
public double NextDouble() { public unsafe double NextDouble() {
byte[] b = new byte[8]; byte[] b = new byte[8];
_GetBytes(b);
if (BitConverter.IsLittleEndian) {
b[7] = 0;
_GetBytes(b, 0, 7);
} else {
b[0] = 0;
_GetBytes(b, 1, 7);
}
ulong r = 0;
fixed(byte* buf = b)
r = *(ulong*)(&buf[0]) >> 3;
/* double: 53 bits of significand precision /* double: 53 bits of significand precision
* ulong.MaxValue >> 11 = 9007199254740991 * ulong.MaxValue >> 11 = 9007199254740991
* 2^53 = 9007199254740992 * 2^53 = 9007199254740992
*/ */
return ((double)(BitConverter.ToUInt64(b, 0) >> 11) / 9007199254740992); return (double)r / 9007199254740992;
} }
} }
@ -348,6 +387,15 @@ namespace Server {
} }
} }
private void _GetBytes(byte[] b, int offset, int count) {
CheckSwap(count);
lock (_sync) {
Buffer.BlockCopy(_Working, _Index, b, offset, count);
_Index += count;
}
}
public int Next(int c) { public int Next(int c) {
return (int)(c * NextDouble()); return (int)(c * NextDouble());
} }
@ -373,16 +421,27 @@ namespace Server {
_GetBytes(b); _GetBytes(b);
} }
public double NextDouble() { public unsafe double NextDouble() {
byte[] b = new byte[8]; byte[] b = new byte[8];
_GetBytes(b);
if (BitConverter.IsLittleEndian) {
b[7] = 0;
_GetBytes(b, 0, 7);
} else {
b[0] = 0;
_GetBytes(b, 1, 7);
}
ulong r = 0;
fixed(byte* buf = b)
r = *(ulong*)(&buf[0]) >> 3;
/* double: 53 bits of significand precision /* double: 53 bits of significand precision
* ulong.MaxValue >> 11 = 9007199254740991 * ulong.MaxValue >> 11 = 9007199254740991
* 2^53 = 9007199254740992 * 2^53 = 9007199254740992
*/ */
return ((double)(BitConverter.ToUInt64(b, 0) >> 11) / 9007199254740992); return (double)r / 9007199254740992;
} }
} }