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/*
* (C) Copyright Nick Thompson 2018.
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
*/
#include "multiprecision_config.hpp"
#ifndef DISABLE_MP_TESTS
#include <boost/integer/mod_inverse.hpp>
#include <boost/cstdint.hpp>
#include <boost/optional/optional.hpp>
#include <boost/core/lightweight_test.hpp>
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/integer/common_factor.hpp>
using boost::multiprecision::int128_t;
using boost::multiprecision::int256_t;
using boost::integer::mod_inverse;
using boost::integer::gcd;
template<class Z>
void test_mod_inverse()
{
//Z max_arg = std::numeric_limits<Z>::max();
Z max_arg = 500;
for (Z modulus = 2; modulus < max_arg; ++modulus)
{
if (modulus % 1000 == 0)
{
std::cout << "Testing all inverses modulo " << modulus << std::endl;
}
for (Z a = 1; a < modulus; ++a)
{
Z gcdam = gcd(a, modulus);
Z inv_a = mod_inverse(a, modulus);
// Should fail if gcd(a, mod) != 1:
if (gcdam > 1)
{
BOOST_TEST(inv_a == 0);
}
else
{
BOOST_TEST(inv_a > 0);
// Cast to a bigger type so the multiplication won't overflow.
int256_t a_inv = inv_a;
int256_t big_a = a;
int256_t m = modulus;
int256_t outta_be_one = (a_inv*big_a) % m;
BOOST_TEST_EQ(outta_be_one, 1);
}
}
}
}
int main()
{
test_mod_inverse<boost::int16_t>();
test_mod_inverse<boost::int32_t>();
test_mod_inverse<boost::int64_t>();
test_mod_inverse<int128_t>();
return boost::report_errors();
}
#else
int main()
{
return 0;
}
#endif
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