/// <summary>
/// Create a minimum perfect hash function for the provided key set
/// </summary>
/// <param name="keySource">Key source</param>
/// <param name="c">Load factor (.5 > c > .99)</param>
/// <returns>Created Minimum Perfect Hash function</returns>
public static MinPerfectHash Create(IKeySource keySource, double c)
{
var buckets = new Buckets(keySource, c);
var dispTable = new uint[buckets.NBuckets];
uint hashSeed;
var iteration = 100;
for (; ; iteration--)
{
uint maxBucketSize;
if (!buckets.MappingPhase(out hashSeed, out maxBucketSize))
{
throw new Exception("Mapping failure. Duplicate keys?");
}
var sortedLists = buckets.OrderingPhase(maxBucketSize);
var searchingSuccess = buckets.SearchingPhase(maxBucketSize, sortedLists, dispTable);
if (searchingSuccess) break;
if (iteration <= 0)
{
throw new Exception("Too many iteration");
}
}
var cs = new CompressedSeq();
cs.Generate(dispTable, (uint)dispTable.Length);
var ret = new MinPerfectHash { _hashSeed = hashSeed, _cs = cs, _nbuckets = buckets.NBuckets, _n = buckets.N };
return ret;
}
/// <summary>
/// Create a minimum perfect hash function for the provided key set
/// </summary>
/// <param name="keySource">Key source</param>
/// <param name="c">Load factor (.5 > c > .99)</param>
/// <returns>Created Minimum Perfect Hash function</returns>
public static MinPerfectHash Create(IKeySource keySource, double c)
{
var buckets = new Buckets(keySource, c);
var dispTable = new uint[buckets.NBuckets];
uint hashSeed;
var iteration = 100;
for (; ; iteration--)
{
uint maxBucketSize;
if (!buckets.MappingPhase(out hashSeed, out maxBucketSize))
{
throw new Exception("Mapping failure. Duplicate keys?");
}
var sortedLists = buckets.OrderingPhase(maxBucketSize);
var searchingSuccess = buckets.SearchingPhase(maxBucketSize, sortedLists, dispTable);
if (searchingSuccess)
{
break;
}
if (iteration <= 0)
{
throw new Exception("Too many iteration");
}
}
var cs = new CompressedSeq();
cs.Generate(dispTable, (uint)dispTable.Length);
var ret = new MinPerfectHash {
_hashSeed = hashSeed, _cs = cs, _nbuckets = buckets.NBuckets, _n = buckets.N
};
return(ret);
}
public Buckets(IKeySource keySource, double c)
{
_keySource = keySource;
var loadFactor = c;
_m = keySource.NbKeys;
_nbuckets = _m / KeysPerBucket + 1;
if (loadFactor < 0.5)
{
loadFactor = 0.5;
}
if (loadFactor >= 0.99)
{
loadFactor = 0.99;
}
_n = (uint)(_m / (loadFactor)) + 1;
if (_n % 2 == 0)
{
_n++;
}
for (;;)
{
if (MillerRabin.CheckPrimality(_n))
{
break;
}
_n += 2; // just odd numbers can be primes for n > 2
}
_buckets = new Bucket[_nbuckets];
_items = new Item[_m];
}
public Buckets(IKeySource keySource, double c)
{
_keySource = keySource;
var loadFactor = c;
_m = keySource.NbKeys;
_nbuckets = _m/KeysPerBucket + 1;
if(loadFactor < 0.5 ) loadFactor = 0.5;
if(loadFactor >= 0.99) loadFactor = 0.99;
_n = (uint)(_m/(loadFactor)) + 1;
if(_n % 2 == 0) _n++;
for(;;)
{
if(MillerRabin.CheckPrimality(_n)) break;
_n += 2; // just odd numbers can be primes for n > 2
}
_buckets = new Bucket[_nbuckets];
_items = new Item[_m];
}
public void RegisterKeySource(IKeySource source)
{
source.OnKeyPress += this.KeyPressHandler;
}
