高性能的Hash算法对我们的应用程序无疑是至关重要的。以下几种Hash的性能很不俗，记录在这里。
1. MurMurHash算法
MurmurHash 是一种非型，适用于一般的哈希检索操作。 由Austin Appleby在2008年发明，并出现了多个变种，都已经发布到了(public domain)。与其它流行的哈希函数相比，对于规律性较强的key，MurmurHash的随机分布特征表现更良好。
以下是MurmurHash官方性能图
以下是官方的算法实现，随手摘来了。
public class Murmur3{ // 128 bit output, 64 bit platform version public static ulong READ_SIZE = 16; private static ulong C1 = 0x87c37b91114253d5L; private static ulong C2 = 0x4cf5ad432745937fL; private ulong length; private uint seed; // if want to start with a seed, create a constructor ulong h1; ulong h2; private void MixBody(ulong k1, ulong k2) { h1 ^= MixKey1(k1); h1 = h1.RotateLeft(27); h1 += h2; h1 = h1 * 5 + 0x52dce729; h2 ^= MixKey2(k2); h2 = h2.RotateLeft(31); h2 += h1; h2 = h2 * 5 + 0x38495ab5; } private static ulong MixKey1(ulong k1) { k1 *= C1; k1 = k1.RotateLeft(31); k1 *= C2; return k1; } private static ulong MixKey2(ulong k2) { k2 *= C2; k2 = k2.RotateLeft(33); k2 *= C1; return k2; } private static ulong MixFinal(ulong k) { // avalanche bits k ^= k >> 33; k *= 0xff51afd7ed558ccdL; k ^= k >> 33; k *= 0xc4ceb9fe1a85ec53L; k ^= k >> 33; return k; } public byte[] ComputeHash(byte[] bb) { ProcessBytes(bb); return Hash; } private void ProcessBytes(byte[] bb) { h1 = seed; this.length = 0L; int pos = 0; ulong remaining = (ulong)bb.Length; // read 128 bits, 16 bytes, 2 longs in eacy cycle while (remaining >= READ_SIZE) { ulong k1 = bb.GetUInt64(pos); pos += 8; ulong k2 = bb.GetUInt64(pos); pos += 8; length += READ_SIZE; remaining -= READ_SIZE; MixBody(k1, k2); } // if the input MOD 16 != 0 if (remaining > 0) ProcessBytesRemaining(bb, remaining, pos); } private void ProcessBytesRemaining(byte[] bb, ulong remaining, int pos) { ulong k1 = 0; ulong k2 = 0; length += remaining; // little endian (x86) processing switch (remaining) { case 15: k2 ^= (ulong)bb[pos + 14] << 48; // fall through goto case 14; case 14: k2 ^= (ulong)bb[pos + 13] << 40; // fall through goto case 13; case 13: k2 ^= (ulong)bb[pos + 12] << 32; // fall through goto case 12; case 12: k2 ^= (ulong)bb[pos + 11] << 24; // fall through goto case 11; case 11: k2 ^= (ulong)bb[pos + 10] << 16; // fall through goto case 10; case 10: k2 ^= (ulong)bb[pos + 9] << 8; // fall through goto case 9; case 9: k2 ^= (ulong)bb[pos + 8]; // fall through goto case 8; case 8: k1 ^= bb.GetUInt64(pos); break; case 7: k1 ^= (ulong)bb[pos + 6] << 48; // fall through goto case 6; case 6: k1 ^= (ulong)bb[pos + 5] << 40; // fall through goto case 5; case 5: k1 ^= (ulong)bb[pos + 4] << 32; // fall through goto case 4; case 4: k1 ^= (ulong)bb[pos + 3] << 24; // fall through goto case 3; case 3: k1 ^= (ulong)bb[pos + 2] << 16; // fall through goto case 2; case 2: k1 ^= (ulong)bb[pos + 1] << 8; // fall through goto case 1; case 1: k1 ^= (ulong)bb[pos]; // fall through break; default: throw new Exception("Something went wrong with remaining bytes calculation."); } h1 ^= MixKey1(k1); h2 ^= MixKey2(k2); } public byte[] Hash { get { h1 ^= length; h2 ^= length; h1 += h2; h2 += h1; h1 = Murmur3.MixFinal(h1); h2 = Murmur3.MixFinal(h2); h1 += h2; h2 += h1; var hash = new byte[Murmur3.READ_SIZE]; Array.Copy(BitConverter.GetBytes(h1), 0, hash, 0, 8); Array.Copy(BitConverter.GetBytes(h2), 0, hash, 8, 8); return hash; } }} 使用方法：
public static class IntHelpers{ public static ulong RotateLeft(this ulong original, int bits) { return (original << bits) | (original >> (64 - bits)); } public static ulong RotateRight(this ulong original, int bits) { return (original >> bits) | (original << (64 - bits)); } unsafe public static ulong GetUInt64(this byte[] bb, int pos) { // we only read aligned longs, so a simple casting is enough fixed (byte* pbyte = &bb[pos]) { return *((ulong*)pbyte); } }}