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// File: TCollection.cxx
// Created: Thu Jan 14 16:15:39 1993
// Author: Remi LEQUETTE
// <rle@phylox>
#include <TCollection.ixx>
// The array of prime numbers used as consequtive steps for
// size of array of buckets in the map.
//
// The prime numbers are used for array size with the hope that this will
// lead to less probablility of having the same hash codes for
// different map items (note that all hash codes are modulo that size).
//
// The value of each next step is chosen to be ~2 times greater than previous.
// Though this could be thought as too much, actually the amount of
// memory overhead in that case is only ~15% as compared with total size of
// all auxiliary data structures (each map node takes ~24 bytes),
// and this proves to pay off in performance (see OCC13189).
#define NB_PRIMES 12
static const Standard_Integer Primes[NB_PRIMES+1] = {
101,
1009,
2003,
5003,
10007,
20011,
37003,
57037,
65003,
100019,
209953, // The following are Pierpont primes taken from Wikipedia [List of prime numbers]
472393,
995329
};
Standard_Integer TCollection::NextPrimeForMap(const Standard_Integer N)
{
Standard_Integer i;
for (i = 0; i < NB_PRIMES; i++)
if (Primes[i] > N) break;
return Primes[i];
}
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