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60 lines
2.2 KiB
C++
Executable File
60 lines
2.2 KiB
C++
Executable File
// Created on: 1993-01-14
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// Created by: Remi LEQUETTE
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// Copyright (c) 1993-1999 Matra Datavision
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// Copyright (c) 1999-2012 OPEN CASCADE SAS
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//
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// The content of this file is subject to the Open CASCADE Technology Public
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// License Version 6.5 (the "License"). You may not use the content of this file
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// except in compliance with the License. Please obtain a copy of the License
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// at http://www.opencascade.org and read it completely before using this file.
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//
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// The Initial Developer of the Original Code is Open CASCADE S.A.S., having its
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// main offices at: 1, place des Freres Montgolfier, 78280 Guyancourt, France.
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//
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// The Original Code and all software distributed under the License is
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// distributed on an "AS IS" basis, without warranty of any kind, and the
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// Initial Developer hereby disclaims all such warranties, including without
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// limitation, any warranties of merchantability, fitness for a particular
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// purpose or non-infringement. Please see the License for the specific terms
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// and conditions governing the rights and limitations under the License.
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#include <TCollection.ixx>
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// The array of prime numbers used as consequtive steps for
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// size of array of buckets in the map.
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// The prime numbers are used for array size with the hope that this will
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// lead to less probablility of having the same hash codes for
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// different map items (note that all hash codes are modulo that size).
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// The value of each next step is chosen to be ~2 times greater than previous.
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// Though this could be thought as too much, actually the amount of
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// memory overhead in that case is only ~15% as compared with total size of
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// all auxiliary data structures (each map node takes ~24 bytes),
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// and this proves to pay off in performance (see OCC13189).
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#define NB_PRIMES 12
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static const Standard_Integer Primes[NB_PRIMES+1] = {
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101,
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1009,
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2003,
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5003,
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10007,
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20011,
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37003,
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57037,
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65003,
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100019,
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209953, // The following are Pierpont primes taken from Wikipedia [List of prime numbers]
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472393,
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995329
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};
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Standard_Integer TCollection::NextPrimeForMap(const Standard_Integer N)
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{
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Standard_Integer i;
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for (i = 0; i < NB_PRIMES; i++)
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if (Primes[i] > N) break;
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return Primes[i];
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}
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