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Speed up construction from ulonglong

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This commit is contained in:
ckormanyos
2025-09-02 20:03:00 +02:00
parent 554bb279fb
commit c46c3bf0a1
2 changed files with 67 additions and 31 deletions
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94
include/boost/multiprecision/cpp_double_fp.hpp
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@@ -281,36 +281,56 @@ class cpp_double_fp_backend
using local_unsigned_integral_type = UnsignedIntegralType;
constexpr local_unsigned_integral_type
flt_mask
limb_mask
{
static_cast<local_unsigned_integral_type>
(
static_cast<local_unsigned_integral_type>
(
static_cast<local_unsigned_integral_type>(UINT8_C(1)) << static_cast<unsigned>(std::numeric_limits<float_type>::digits)
)
- static_cast<local_unsigned_integral_type>(UINT8_C(1))
)
local_unsigned_integral_type { local_unsigned_integral_type { 1 } << static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits) }
- local_unsigned_integral_type { 1 }
};
data.second = static_cast<float_type>(0.0F);
data.first = static_cast<float_type>(u & flt_mask);
float_type p2_flt { cpp_df_qf_detail::ccmath::ldexp(float_type { 1 }, std::numeric_limits<float_type>::digits) };
while (u > static_cast<local_unsigned_integral_type>(UINT8_C(0)))
if (u <= limb_mask)
{
u >>= static_cast<unsigned>(std::numeric_limits<float_type>::digits);
const float_type
xhi
data =
{
static_cast<float_type>(u),
static_cast<float_type>(0.0F)
};
}
else
{
constexpr local_unsigned_integral_type
flt_mask
{
static_cast<float_type>(u & flt_mask) * p2_flt
static_cast<local_unsigned_integral_type>
(
static_cast<local_unsigned_integral_type>
(
static_cast<local_unsigned_integral_type>(UINT8_C(1)) << static_cast<unsigned>(std::numeric_limits<float_type>::digits)
)
- static_cast<local_unsigned_integral_type>(UINT8_C(1))
)
};
eval_add(*this, cpp_double_fp_backend(xhi));
data.second = static_cast<float_type>(0.0F);
data.first = static_cast<float_type>(u & flt_mask);
p2_flt = cpp_df_qf_detail::ccmath::ldexp(p2_flt, std::numeric_limits<float_type>::digits);
constexpr float_type p2_factor_digits { cpp_df_qf_detail::ccmath::ldexp(static_cast<float_type>(1.0F), std::numeric_limits<float_type>::digits) };
float_type p2_factor { p2_factor_digits };
while (u > static_cast<local_unsigned_integral_type>(UINT8_C(0)))
{
u >>= static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits);
const float_type
xhi
{
static_cast<float_type>(u & flt_mask) * p2_factor
};
add_unchecked_limb(xhi);
p2_factor *= p2_factor_digits;
}
}
}
@@ -526,13 +546,7 @@ class cpp_double_fp_backend
}
}
const rep_type thi_tlo { arithmetic::two_sum(data.second, v.data.second) };
data = arithmetic::two_sum(data.first, v.data.first);
data = arithmetic::two_hilo_sum(data.first, data.second + thi_tlo.first);
data = arithmetic::two_hilo_sum(data.first, thi_tlo.second + data.second);
add_unchecked(v);
return *this;
}
@@ -1053,6 +1067,28 @@ class cpp_double_fp_backend
auto rd_string(const char* pstr) -> bool;
constexpr auto add_unchecked(const cpp_double_fp_backend& v) -> void
{
const rep_type thi_tlo { arithmetic::two_sum(data.second, v.data.second) };
data = arithmetic::two_sum(data.first, v.data.first);
data = arithmetic::two_hilo_sum(data.first, data.second + thi_tlo.first);
data = arithmetic::two_hilo_sum(data.first, thi_tlo.second + data.second);
}
constexpr auto add_unchecked_limb(const float_type v_first) -> void
{
const rep_type thi_tlo { data.second, static_cast<float_type>(0.0F) };
data = arithmetic::two_sum(data.first, v_first);
data = arithmetic::two_hilo_sum(data.first, data.second + thi_tlo.first);
data = arithmetic::two_hilo_sum(data.first, data.second);
}
constexpr auto mul_unchecked(const cpp_double_fp_backend& v) -> void
{
// The multiplication algorithm has been taken from Victor Shoup,

4
test/test_arithmetic_df.cpp
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@@ -20,9 +20,9 @@ auto test_constexpr_ness() noexcept -> void
constexpr local_float_type one { 1 };
static_assert(static_cast<int>(one) == 1, "Error: constexpr local_float_type construction failed");
static_assert(one == 1, "Error: constexpr local_float_type construction failed");
BOOST_CHECK(static_cast<int>(one) == 1);
BOOST_CHECK(one == 1);
constexpr local_float_type dd_a { 1.23 };
constexpr local_float_type dd_b { 4.56 };