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74 lines
2.0 KiB
C++
74 lines
2.0 KiB
C++
/*
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* (C) Copyright Nick Thompson 2018.
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* Use, modification and distribution are subject to the
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* Boost Software License, Version 1.0. (See accompanying file
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* LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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*/
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#include <boost/config.hpp>
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#if (defined(BOOST_MSVC) && (BOOST_MSVC < 1500)) || \
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(defined(__clang_major__) && (__clang_major__ == 3) && (__clang_minor__ < 2)) || \
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(defined(BOOST_GCC) && defined(BOOST_GCC_CXX11) && BOOST_GCC < 40800)
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#define DISABLE_MP_TESTS
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#endif
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#ifndef DISABLE_MP_TESTS
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#include <boost/core/lightweight_test.hpp>
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#include <boost/multiprecision/cpp_int.hpp>
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#include <boost/integer/common_factor.hpp>
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#include <boost/integer/mod_inverse.hpp>
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using boost::multiprecision::int128_t;
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using boost::multiprecision::int256_t;
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using boost::integer::mod_inverse;
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using boost::integer::gcd;
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template<class Z>
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void test_mod_inverse()
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{
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//Z max_arg = std::numeric_limits<Z>::max();
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Z max_arg = 500;
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for (Z modulus = 2; modulus < max_arg; ++modulus)
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{
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if (modulus % 1000 == 0)
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{
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std::cout << "Testing all inverses modulo " << modulus << std::endl;
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}
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for (Z a = 1; a < modulus; ++a)
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{
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Z gcdam = gcd(a, modulus);
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boost::optional<Z> inv_a = mod_inverse(a, modulus);
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// Should fail if gcd(a, mod) != 1:
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if (gcdam > 1)
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{
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BOOST_TEST(!inv_a);
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}
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else
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{
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BOOST_TEST(inv_a.value() > 0);
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// Cast to a bigger type so the multiplication won't overflow.
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int256_t a_inv = inv_a.value();
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int256_t big_a = a;
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int256_t m = modulus;
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int256_t outta_be_one = (a_inv*big_a) % m;
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BOOST_TEST_EQ(outta_be_one, 1);
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}
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}
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}
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}
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int main()
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{
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test_mod_inverse<int16_t>();
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test_mod_inverse<int32_t>();
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test_mod_inverse<int64_t>();
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test_mod_inverse<int128_t>();
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return boost::report_errors();
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}
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#else
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int main()
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{
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return 0;
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}
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#endif
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