public void CacheReadReference(string cacheBlock)
{
this.refreshCounter++; //increment the refresh counter
this.totalCacheReferences++; //Increment the total number of references we've seen in the cache so far
Int32 blockIndex = -1;
byte[] hashedByteValue = this.Murmur3HashFunction.ComputeHash(System.Text.Encoding.UTF8.GetBytes(cacheBlock));
UInt64 hashedValue = IntHelpers.GetUInt64(hashedByteValue, 8);
if ((hashedValue & (this.modulusP - 1)) < this.thresholdT)
{
this.totalProcessedReferences++;
GhostCacheElement ghostBlock = null;
if (this.hashTableLookup.TryGetValue(hashedValue, out ghostBlock)) //O(1)
{ //hit, it's in the ghost cache
blockIndex = this.distanceTree.IndexOfKey(ghostBlock.refreshCounter); // O(log n)
Int32 scaledReuseDistance = (Int32)Math.Round((double)blockIndex / this.samplingRateR);
ghostBlock.refreshCounter = this.refreshCounter; //update counter in the block
//update the counter at its current depth
Debug.Assert(this.reuseAccessHistogram[scaledReuseDistance] + 1 < UInt32.MaxValue); //make sure we don't overflow the counter
this.reuseAccessHistogram[scaledReuseDistance] += 1;
//Move it to the right place in the stack (new counter value == "0th position")
this.distanceTree.RemoveAt(blockIndex); //O(log n)
this.distanceTree.Add(this.refreshCounter, ghostBlock); //O(log n)
}
else
{
this.Evict(); //check if we need to free up space (should rarely have to...)
ghostBlock = new GhostCacheElement(refreshCounter, hashedValue);
this.distanceTree.Add(refreshCounter, ghostBlock);
this.hashTableLookup.Add(hashedValue, ghostBlock);
this.coldMisses++; //this is only true (ie: a cold miss) until the ghost cache has to start evicting things
}
}
}
public byte[] ComputeHash(byte[] bb)
{
ulong h1 = 0L;
ulong h2 = 0L;
h1 = seed;
ulong 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 = IntHelpers.GetUInt64(bb, pos);
pos += 8;
ulong k2 = IntHelpers.GetUInt64(bb, pos);
pos += 8;
length += READ_SIZE;
remaining -= READ_SIZE;
//Used to be MixBody(k1, k2);
k1 *= C1;
k1 = IntHelpers.RotateLeft(k1, 31);
k1 *= C2;
h1 ^= k1; //was h1 ^= MixKey1(k1);
h1 = IntHelpers.RotateLeft(h1, 27);
h1 += h2;
h1 = h1 * 5 + 0x52dce729;
k2 *= C2;
k2 = IntHelpers.RotateLeft(k2, 33);
k2 *= C1;
h2 ^= k2; //was h2 ^= MixKey2(k2);
h2 = IntHelpers.RotateLeft(h2, 31);
h2 += h1;
h2 = h2 * 5 + 0x38495ab5;
}
// if the input MOD 16 != 0
if (remaining > 0)
{
//ProcessBytesRemaining(bb, remaining, pos);
ulong j1 = 0;
ulong j2 = 0;
length += remaining;
// little endian (x86) processing
switch (remaining)
{
case 15:
j2 ^= (ulong)bb[pos + 14] << 48; // fall through
goto case 14;
case 14:
j2 ^= (ulong)bb[pos + 13] << 40; // fall through
goto case 13;
case 13:
j2 ^= (ulong)bb[pos + 12] << 32; // fall through
goto case 12;
case 12:
j2 ^= (ulong)bb[pos + 11] << 24; // fall through
goto case 11;
case 11:
j2 ^= (ulong)bb[pos + 10] << 16; // fall through
goto case 10;
case 10:
j2 ^= (ulong)bb[pos + 9] << 8; // fall through
goto case 9;
case 9:
j2 ^= (ulong)bb[pos + 8]; // fall through
goto case 8;
case 8:
j1 ^= bb.GetUInt64(pos);
break;
case 7:
j1 ^= (ulong)bb[pos + 6] << 48; // fall through
goto case 6;
case 6:
j1 ^= (ulong)bb[pos + 5] << 40; // fall through
goto case 5;
case 5:
j1 ^= (ulong)bb[pos + 4] << 32; // fall through
goto case 4;
case 4:
j1 ^= (ulong)bb[pos + 3] << 24; // fall through
goto case 3;
case 3:
j1 ^= (ulong)bb[pos + 2] << 16; // fall through
goto case 2;
case 2:
j1 ^= (ulong)bb[pos + 1] << 8; // fall through
goto case 1;
case 1:
j1 ^= (ulong)bb[pos]; // fall through
break;
default:
throw new Exception("Something went wrong with remaining bytes calculation.");
}
j1 *= C1;
j1 = IntHelpers.RotateLeft(j1, 31);
j1 *= C2;
h1 ^= j1;
j2 *= C2;
j2 = IntHelpers.RotateLeft(j2, 33);
j2 *= C1;
h2 ^= j2;
}
/////////////////////////////////////
//// BELOW WAS ALL return Hash;
/////////////////////////////////////
h1 ^= length;
h2 ^= length;
h1 += h2;
h2 += h1;
//h1 = Murmur3.MixFinal(h1);
h1 ^= h1 >> 33;
h1 *= 0xff51afd7ed558ccdL;
h1 ^= h1 >> 33;
h1 *= 0xc4ceb9fe1a85ec53L;
h1 ^= h1 >> 33;
//h2 = Murmur3.MixFinal(h2);
h2 ^= h2 >> 33;
h2 *= 0xff51afd7ed558ccdL;
h2 ^= h2 >> 33;
h2 *= 0xc4ceb9fe1a85ec53L;
h2 ^= h2 >> 33;
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);
}
