mirror of
https://git.dev.opencascade.org/repos/occt.git
synced 2025-04-10 18:51:21 +03:00
75 lines
2.5 KiB
C++
75 lines
2.5 KiB
C++
// Created on: 1993-01-14
|
|
// Created by: Remi LEQUETTE
|
|
// Copyright (c) 1993-1999 Matra Datavision
|
|
// Copyright (c) 1999-2014 OPEN CASCADE SAS
|
|
//
|
|
// This file is part of Open CASCADE Technology software library.
|
|
//
|
|
// This library is free software; you can redistribute it and/or modify it under
|
|
// the terms of the GNU Lesser General Public License version 2.1 as published
|
|
// by the Free Software Foundation, with special exception defined in the file
|
|
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
|
|
// distribution for complete text of the license and disclaimer of any warranty.
|
|
//
|
|
// Alternatively, this file may be used under the terms of Open CASCADE
|
|
// commercial license or contractual agreement.
|
|
|
|
#include <TCollection.hxx>
|
|
|
|
#include <Standard_OutOfRange.hxx>
|
|
|
|
// The array of prime numbers used as consecutive 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 THE_NB_PRIMES 24
|
|
static const Standard_Integer THE_TCollection_Primes[THE_NB_PRIMES] =
|
|
{
|
|
101,
|
|
1009,
|
|
2003,
|
|
5003,
|
|
10007,
|
|
20011,
|
|
37003,
|
|
57037,
|
|
65003,
|
|
100019,
|
|
209953, // The following are Pierpont primes [List of prime numbers]
|
|
472393,
|
|
995329,
|
|
2359297,
|
|
4478977,
|
|
9437185,
|
|
17915905,
|
|
35831809,
|
|
71663617,
|
|
150994945,
|
|
301989889,
|
|
573308929,
|
|
1019215873,
|
|
2038431745
|
|
};
|
|
|
|
// =======================================================================
|
|
// function : NextPrimeForMap
|
|
// purpose :
|
|
// =======================================================================
|
|
Standard_Integer TCollection::NextPrimeForMap(const Standard_Integer N)
|
|
{
|
|
for (Standard_Integer aPrimeIter = 0; aPrimeIter < THE_NB_PRIMES; ++aPrimeIter)
|
|
{
|
|
if (THE_TCollection_Primes[aPrimeIter] > N)
|
|
{
|
|
return THE_TCollection_Primes[aPrimeIter];
|
|
}
|
|
}
|
|
throw Standard_OutOfRange ("TCollection::NextPrimeForMap() - requested too big size");
|
|
}
|