/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*

 Copyright (C) 2003 Ferdinando Ametrano

 This file is part of QuantLib, a free-software/open-source library

 for financial quantitative analysts and developers - http://quantlib.org/

 QuantLib is free software: you can redistribute it and/or modify it

 under the terms of the QuantLib license.  You should have received a

 copy of the license along with this program; if not, please email

 <quantlib-dev@lists.sf.net>. The license is also available online at

 <http://quantlib.org/license.shtml>.

 This program is distributed in the hope that it will be useful, but WITHOUT

 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 FOR A PARTICULAR PURPOSE.  See the license for more details.

*/

// ===========================================================================

// NOTE: The following copyright notice applies to the original code,

//

// Copyright (C) 2002 Peter Jäckel "Monte Carlo Methods in Finance".

// All rights reserved.

//

// Permission to use, copy, modify, and distribute this software is freely

// granted, provided that this notice is preserved.

// ===========================================================================

#include <ql/math/primenumbers.hpp>

#include <iterator>

namespace QuantLib {

    namespace {

        const BigNatural firstPrimes[] = {

            // the first two primes are mandatory for bootstrapping

            2,  3,

            // optional additional precomputed primes

            5,  7, 11, 13, 17, 19, 23, 29,

            31, 37, 41, 43, 47 };

    }

    std::vector<BigNatural> PrimeNumbers::primeNumbers_;

    BigNatural PrimeNumbers::get(Size absoluteIndex) {

        if (primeNumbers_.empty()) {

            Size n = sizeof(firstPrimes)/sizeof(firstPrimes[0]);

            primeNumbers_.insert(primeNumbers_.end(),

                                 firstPrimes, firstPrimes+n);

        }

        while (primeNumbers_.size()<=absoluteIndex)

            nextPrimeNumber();

        return primeNumbers_[absoluteIndex];

    }

    BigNatural PrimeNumbers::nextPrimeNumber() {

        BigNatural p, n, m = primeNumbers_.back();

        do {

            // skip the even numbers

            m += 2;

            n = static_cast<BigNatural>(std::sqrt(Real(m)));

            // i=1 since the even numbers have already been skipped

            Size i = 1;

            do {

                p = primeNumbers_[i];

                ++i;

            } while (((m % p) != 0U) && p <= n);

        } while ( p<=n );

        primeNumbers_.push_back(m);

        return m;

    }

}