121 lines
3.4 KiB
C#
121 lines
3.4 KiB
C#
//
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// Mono.Math.Prime.Generator.SequentialSearchPrimeGeneratorBase.cs - Prime Generator
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//
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// Authors:
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// Ben Maurer
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//
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// Copyright (c) 2003 Ben Maurer. All rights reserved
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// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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namespace Mono.Math.Prime.Generator {
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#if INSIDE_CORLIB
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internal
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#else
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public
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#endif
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class SequentialSearchPrimeGeneratorBase : PrimeGeneratorBase {
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protected virtual BigInteger GenerateSearchBase (int bits, object context)
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{
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BigInteger ret = BigInteger.GenerateRandom (bits);
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ret.SetBit (0);
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return ret;
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}
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public override BigInteger GenerateNewPrime (int bits)
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{
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return GenerateNewPrime (bits, null);
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}
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public virtual BigInteger GenerateNewPrime (int bits, object context)
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{
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//
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// STEP 1. Find a place to do a sequential search
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//
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BigInteger curVal = GenerateSearchBase (bits, context);
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const uint primeProd1 = 3u* 5u * 7u * 11u * 13u * 17u * 19u * 23u * 29u;
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uint pMod1 = curVal % primeProd1;
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int DivisionBound = TrialDivisionBounds;
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uint[] SmallPrimes = BigInteger.smallPrimes;
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//
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// STEP 2. Search for primes
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//
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while (true) {
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//
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// STEP 2.1 Sieve out numbers divisible by the first 9 primes
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//
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if (pMod1 % 3 == 0) goto biNotPrime;
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if (pMod1 % 5 == 0) goto biNotPrime;
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if (pMod1 % 7 == 0) goto biNotPrime;
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if (pMod1 % 11 == 0) goto biNotPrime;
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if (pMod1 % 13 == 0) goto biNotPrime;
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if (pMod1 % 17 == 0) goto biNotPrime;
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if (pMod1 % 19 == 0) goto biNotPrime;
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if (pMod1 % 23 == 0) goto biNotPrime;
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if (pMod1 % 29 == 0) goto biNotPrime;
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//
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// STEP 2.2 Sieve out all numbers divisible by the primes <= DivisionBound
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//
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for (int p = 10; p < SmallPrimes.Length && SmallPrimes [p] <= DivisionBound; p++) {
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if (curVal % SmallPrimes [p] == 0)
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goto biNotPrime;
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}
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//
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// STEP 2.3 Is the potential prime acceptable?
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//
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if (!IsPrimeAcceptable (curVal, context))
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goto biNotPrime;
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//
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// STEP 2.4 Filter out all primes that pass this step with a primality test
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//
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if (PrimalityTest (curVal, Confidence))
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return curVal;
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//
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// STEP 2.4
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//
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biNotPrime:
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pMod1 += 2;
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if (pMod1 >= primeProd1)
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pMod1 -= primeProd1;
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curVal.Incr2 ();
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}
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}
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protected virtual bool IsPrimeAcceptable (BigInteger bi, object context)
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{
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return true;
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}
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}
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}
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