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Merged
cyberjunk merged 9 commits into from
Jan 11, 2026
Merged

upowmod k-ary #110

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d1f676c
wip
cyberjunk Dec 21, 2025
5117a1d
Merge branch 'master' of ssh://github.com/cyberjunk/cppcore into feat…
cyberjunk Jan 3, 2026
3cb7743
wip
cyberjunk Jan 3, 2026
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cyberjunk Jan 3, 2026
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cyberjunk Jan 3, 2026
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cyberjunk Jan 9, 2026
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cyberjunk Jan 10, 2026
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cyberjunk Jan 11, 2026
08dc865
cleanup
cyberjunk Jan 11, 2026
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20 changes: 20 additions & 0 deletions include/CppCore.Test/Math/Util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -894,6 +894,24 @@ namespace CppCore { namespace Test { namespace Math
return true;
}

template<size_t N64=2>
INLINE static bool upowmod()
{
uint64_t a1[N64]; uint64_t b1[N64]; uint64_t m1[N64]; uint64_t r1[N64];
uint64_t a2[N64]; uint64_t b2[N64]; uint64_t m2[N64]; uint64_t r2[N64];
CppCore::Random::Default64 prng;
for (size_t i = 0; i < 100; i++) {
prng.fill(a1); CppCore::clone(a2, a1);
prng.fill(b1); CppCore::clone(b2, b1);
prng.fill(m1); CppCore::clone(m2, m1);
CppCore::upowmod_single(a1, b1, m1, r1);
CppCore::upowmod(a2, b2, m2, r2);
if (!CppCore::equal(r1, r2))
return false;
}
return true;
}

INLINE static bool upow32()
{
for (uint32_t base = 0; base < 20; base++)
Expand Down Expand Up @@ -1553,6 +1571,8 @@ namespace CppCore { namespace Test { namespace VS { namespace Math {
TEST_METHOD(UMULMOD64) { Assert::AreEqual(true, CppCore::Test::Math::Util::umulmod64()); }
TEST_METHOD(UPOWMOD32) { Assert::AreEqual(true, CppCore::Test::Math::Util::upowmod32()); }
TEST_METHOD(UPOWMOD64) { Assert::AreEqual(true, CppCore::Test::Math::Util::upowmod64()); }
TEST_METHOD(UPOWMOD128) { Assert::AreEqual(true, CppCore::Test::Math::Util::upowmod<2>()); }
TEST_METHOD(UPOWMOD256) { Assert::AreEqual(true, CppCore::Test::Math::Util::upowmod<4>()); }
TEST_METHOD(UPOW32) { Assert::AreEqual(true, CppCore::Test::Math::Util::upow32()); }
TEST_METHOD(UPOW64) { Assert::AreEqual(true, CppCore::Test::Math::Util::upow64()); }
TEST_METHOD(UDIVMOD32) { Assert::AreEqual(true, CppCore::Test::Math::Util::udivmod32()); }
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2 changes: 1 addition & 1 deletion include/CppCore/Math/Primes.h
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Expand Up @@ -122,7 +122,7 @@ namespace CppCore
/// SPRP with precalculated t, s and d and work memory m
/// </summary>
template<typename UINT>
INLINE static bool sprp(const UINT& n, UINT& a, const UINT& t, const uint32_t& s, const UINT& d, UINT& r, UINT m[3])
INLINE static bool sprp(const UINT& n, const UINT& a, const UINT& t, const uint32_t& s, const UINT& d, UINT& r, UINT m[3])
{
assert(a != 1U);
CppCore::upowmod(a, d, n, r, m);
Expand Down
59 changes: 56 additions & 3 deletions include/CppCore/Math/Util.h
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Expand Up @@ -3822,7 +3822,7 @@ namespace CppCore
/// a^b mod m
/// </summary>
template<typename UINT>
INLINE static void upowmod(UINT& a, const UINT& b, const UINT& m, UINT& r, UINT t[3])
INLINE static void upowmod_single(UINT& a, const UINT& b, const UINT& m, UINT& r, UINT t[3])
{
assert((&a != &r) && (&b != &r) && (&m != &r));
assert(!CppCore::testzero(m));
Expand All @@ -3848,10 +3848,63 @@ namespace CppCore
/// a^b mod m
/// </summary>
template<typename UINT>
INLINE static void upowmod(UINT& a, const UINT& b, const UINT& m, UINT& r)
INLINE static void upowmod_single(UINT& a, const UINT& b, const UINT& m, UINT& r)
{
CPPCORE_ALIGN_OPTIM(UINT) t[3];
CppCore::upowmod(a, b, m, r, t);
CppCore::upowmod_single(a, b, m, r, t);
}

/// <summary>
/// a^b mod m
/// </summary>
template<typename UINT, uint32_t K = 4U>
INLINE static void upowmod(const UINT& a, const UINT& b, const UINT& m, UINT& r, UINT t[3])
{
assert((&a != &r) && (&b != &r) && (&m != &r));
assert(!CppCore::testzero(m));
CppCore::clear(r);
constexpr auto NUMBITS = sizeof(UINT)*8U;
const auto LZB = CppCore::lzcnt(b);
if (LZB == NUMBITS) CPPCORE_UNLIKELY {
if (NUMBITS-CppCore::lzcnt(m) != 1U) CPPCORE_LIKELY
*(uint32_t*)&r = 1U;
return;
}
*(uint32_t*)&r = 1U;

// Precompute powers: base^0, base^1, ..., base^(2^k - 1)
constexpr size_t TABLE_SIZE = 1U << K;
CPPCORE_ALIGN_OPTIM(UINT) powers[TABLE_SIZE];
CppCore::clear(powers[0]); *(uint32_t*)&powers[0] = 1U;
CppCore::clone(powers[1], a);
for (size_t i = 2; i < TABLE_SIZE; i++)
CppCore::umulmod(powers[i-1], a, m, powers[i], t);

// Find the position of the highest bit in exp
// Round up to multiple of k
const auto HIDX = NUMBITS - LZB;
const auto HIDX_K = ((HIDX + K - 1U) / K) * K;

// Process k bits at a time from left to right (MSB to LSB)
for (int pos = HIDX_K - K; pos >= 0; pos -= K) {

if (pos < HIDX_K - K)
for (size_t i = 0; i < K; i++)
CppCore::umulmod(r, r, m, r, t);
const uint32_t N = MIN(K, NUMBITS-pos);
const uint32_t CHUNK = CppCore::getbits32(b, pos, N);
CppCore::umulmod(r, powers[CHUNK], m, r, t);
}
}

/// <summary>
/// a^b mod m
/// </summary>
template<typename UINT, uint32_t K = 4U>
INLINE static void upowmod(const UINT& a, const UINT& b, const UINT& m, UINT& r)
{
CPPCORE_ALIGN_OPTIM(UINT) t[3];
CppCore::upowmod<UINT, K>(a, b, m, r, t);
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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2 changes: 2 additions & 0 deletions src/CppCore.Test/Test.cpp
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Expand Up @@ -378,6 +378,8 @@ int main()
TEST(CppCore::Test::Math::Util::umulmod64, "umulmod64: ", std::endl);
TEST(CppCore::Test::Math::Util::upowmod32, "upowmod32: ", std::endl);
TEST(CppCore::Test::Math::Util::upowmod64, "upowmod64: ", std::endl);
TEST(CppCore::Test::Math::Util::upowmod<2>, "upowmod128: ", std::endl);
TEST(CppCore::Test::Math::Util::upowmod<4>, "upowmod256: ", std::endl);
TEST(CppCore::Test::Math::Util::upow32, "upow32: ", std::endl);
TEST(CppCore::Test::Math::Util::upow64, "upow64: ", std::endl);
TEST(CppCore::Test::Math::Util::udivmod32, "udivmod32: ", std::endl);
Expand Down