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cppalliance · May 1, 2024 · 214d730 · 214d730
1 parent 618889c
commit 214d730
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Showing 2 changed files with 28 additions and 1 deletion.
diff --git a/include/boost/decimal/detail/cmath/impl/taylor_series_result.hpp b/include/boost/decimal/detail/cmath/impl/taylor_series_result.hpp
@@ -27,6 +27,27 @@ constexpr auto taylor_series_result(T x, const Array &coeffs) noexcept
     return result;
 }
 
+template <typename Array>
+constexpr auto taylor_series_result(boost::decimal::decimal128 x, const Array &coeffs) noexcept
+{
+    const std::size_t N = coeffs.size();
+
+    auto result = coeffs[N - 1];
+
+    auto my_own_fma =
+        [](boost::decimal::decimal128 x, boost::decimal::decimal128 y, boost::decimal::decimal128 z)
+        {
+            return (x * y) + z;
+        };
+
+    for (std::size_t i = N - 1; i-- > 0;)
+    {
+        result = my_own_fma(result, x, coeffs[i]);
+    }
+
+    return result;
+}
+
 } //namespace detail
 } //namespace decimal
 } //namespace boost

diff --git a/include/boost/decimal/detail/cmath/tgamma.hpp b/include/boost/decimal/detail/cmath/tgamma.hpp
@@ -99,8 +99,14 @@ constexpr auto tgamma_impl(T x) noexcept
                     z = z - nx;
                 }
 
+                auto my_own_fma =
+                    [](T x, T y, T z)
+                    {
+                        return (x * y) + z;
+                    };
+
                 result = detail::tgamma_series_expansion(z);
-                result = one / (z * fma(result, z, one));
+                result = one / (z * my_own_fma(result, z, one));
 
                 if (x_is_gt_one)
                 {