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Switch to series expansion method for ln() (#6268)

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* Switch to series expansion method for ln()
Add float lg() tests to Number tests;
* Rename lg -> log10
* Add check for 0 to log10()
This commit is contained in:
Olek
2026-01-26 14:04:03 -05:00
committed by GitHub
parent df98db1452
commit 4160677878
5 changed files with 133 additions and 24 deletions
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84
src/test/basics/Number_test.cpp
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@@ -1712,6 +1712,89 @@ public:
}
}
void
test_log10()
{
auto const scale = Number::getMantissaScale();
testcase << "test_lg " << to_string(scale);
using Case = std::tuple<Number, Number>;
auto test = [this](auto const& c) {
for (auto const& [x, z] : c)
{
auto const result = log10(x);
std::stringstream ss;
ss << "lg(" << x << ") = " << result << ". Expected: " << z;
// std::cout << ss.str() << std::endl;
BEAST_EXPECTS(result == z, ss.str());
}
};
auto const cSmall = std::to_array<Case>(
{{Number{2}, Number{3'010'299'956'639'811ll, -16}},
{Number{2'000'000}, Number{6'301'029'995'663'985ll, -15}},
{Number{2, -30}, Number{-2'969'897'000'433'602ll, -14}},
{Number{1}, Number{0}},
{Number{1'000'000'000'000'000ll}, Number{15}},
{Number{5625, -4}, Number{-2'498'774'732'165'998, -16}}});
auto const cLarge = std::to_array<Case>(
{{Number{
false, Number::maxMantissa() - 9, -1, Number::normalized{}},
Number{
false,
1'746'901'684'478'673'451ll,
-17,
Number::normalized{}}},
{Number{false, Number::maxMantissa() - 9, 0, Number::normalized{}},
Number{
false,
1'846'901'684'478'673'451ll,
-17,
Number::normalized{}}},
{Number{Number::maxRep},
Number{
false,
1'861'728'612'932'620'011ll,
-17,
Number::normalized{}}}});
if (Number::getMantissaScale() == MantissaRange::small)
{
test(cSmall);
}
else
{
NumberRoundModeGuard mg(Number::towards_zero);
test(cLarge);
}
{
bool caught = false;
try
{
log10(Number{-2});
}
catch (std::runtime_error const&)
{
caught = true;
}
BEAST_EXPECT(caught);
caught = false;
try
{
log10(Number());
}
catch (std::runtime_error const&)
{
caught = true;
}
BEAST_EXPECT(caught);
caught = false;
}
}
void
run() override
{
@@ -1739,6 +1822,7 @@ public:
test_truncate();
testRounding();
testInt64();
test_log10();
}
}
};