Adding scalar_of helper

Chowdhury-DSP · Nov 22, 2023 · 9924fe0 · 9924fe0
1 parent 19c2885
commit 9924fe0
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Showing 3 changed files with 55 additions and 30 deletions.
diff --git a/include/math_approx/src/basic_math.hpp b/include/math_approx/src/basic_math.hpp
@@ -13,6 +13,14 @@
 
 namespace math_approx
 {
+template <typename T>
+struct scalar_of
+{
+    using type = T;
+};
+template <typename T>
+using scalar_of_t = typename scalar_of<T>::type;
+
 template <typename T>
 T rsqrt (T x)
 {
@@ -29,14 +37,21 @@ T rsqrt (T x)
 }
 
 #if defined(XSIMD_HPP)
+template <typename T>
+struct scalar_of<xsimd::batch<T>>
+{
+    using type = T;
+};
+
 template <typename T>
 xsimd::batch<T> rsqrt (xsimd::batch<T> x)
 {
+    using S = scalar_of_t<T>;
     auto r = xsimd::rsqrt (x);
     x *= r;
     x *= r;
-    x += -3.0f;
-    r *= -0.5f;
+    x += (S) -3;
+    r *= (S) -0.5;
     return x * r;
 }
 #endif

diff --git a/include/math_approx/src/sigmoid_approx.hpp b/include/math_approx/src/sigmoid_approx.hpp
@@ -1,7 +1,6 @@
 #pragma once
 
 #include "basic_math.hpp"
-// #include "pow_approx.hpp"
 
 namespace math_approx
 {
@@ -12,38 +11,42 @@ namespace sigmoid_detail
     template <typename T>
     T sig_poly_9 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_7_9 = (T) 1.50024356624e-6 + (T) 6.92468584642e-9 * x_sq;
-        const auto y_5_7_9 = (T) 0.000260923534301 + y_7_9 * x_sq;
-        const auto y_3_5_7_9 = (T) 0.0208320229264 + y_5_7_9 * x_sq;
-        const auto y_1_3_5_7_9 = (T) 0.5 + y_3_5_7_9 * x_sq;
+        const auto y_7_9 = (S) 1.50024356624e-6 + (S) 6.92468584642e-9 * x_sq;
+        const auto y_5_7_9 = (S) 0.000260923534301 + y_7_9 * x_sq;
+        const auto y_3_5_7_9 = (S) 0.0208320229264 + y_5_7_9 * x_sq;
+        const auto y_1_3_5_7_9 = (S) 0.5 + y_3_5_7_9 * x_sq;
         return x * y_1_3_5_7_9;
     }
 
     template <typename T>
     T sig_poly_7 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_5_7 = (T) 0.000255174491559 + (T) 1.90805380557e-6 * x_sq;
-        const auto y_3_5_7 = (T) 0.0208503675870 + y_5_7 * x_sq;
-        const auto y_1_3_5_7 = (T) 0.5 + y_3_5_7 * x_sq;
+        const auto y_5_7 = (S) 0.000255174491559 + (S) 1.90805380557e-6 * x_sq;
+        const auto y_3_5_7 = (S) 0.0208503675870 + y_5_7 * x_sq;
+        const auto y_1_3_5_7 = (S) 0.5 + y_3_5_7 * x_sq;
         return x * y_1_3_5_7;
     }
 
     template <typename T>
     T sig_poly_5 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_3_5 = (T) 0.0206108521251 + (T) 0.000307906311109 * x_sq;
-        const auto y_1_3_5 = (T) 0.5 + y_3_5 * x_sq;
+        const auto y_3_5 = (S) 0.0206108521251 + (S) 0.000307906311109 * x_sq;
+        const auto y_1_3_5 = (S) 0.5 + y_3_5 * x_sq;
         return x * y_1_3_5;
     }
 
     template <typename T>
     T sig_poly_3 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_1_3 = (T) 0.5 + (T) 0.0233402955195 * x_sq;
+        const auto y_1_3 = (S) 0.5 + (S) 0.0233402955195 * x_sq;
         return x * y_1_3;
     }
 } // namespace sigmoid_detail
@@ -63,7 +66,8 @@ T sigmoid (T x)
     else if constexpr (order == 3)
         x_poly = sigmoid_detail::sig_poly_3 (x);
 
-    return (T) 0.5 * x_poly * rsqrt (x_poly * x_poly + (T) 1) + (T) 0.5;
+    using S = scalar_of_t<T>;
+    return (S) 0.5 * x_poly * rsqrt (x_poly * x_poly + (S) 1) + (S) 0.5;
 }
 
 // So far this has tested slower than the above approx (for equivalent error),

diff --git a/include/math_approx/src/tanh_approx.hpp b/include/math_approx/src/tanh_approx.hpp
@@ -11,50 +11,55 @@ namespace tanh_detail
     template <typename T>
     T tanh_poly_11 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_9_11 = (T) 2.63661358122e-6 + (T) 3.33765558362e-8 * x_sq;
-        const auto y_7_9_11 = (T) 0.000199027336899 + y_9_11 * x_sq;
-        const auto y_5_7_9_11 = (T) 0.00833223857843 + y_7_9_11 * x_sq;
-        const auto y_3_5_7_9_11 = (T) 0.166667159320 + y_5_7_9_11 * x_sq;
-        const auto y_1_3_5_7_9_11 = (T) 1 + y_3_5_7_9_11 * x_sq;
+        const auto y_9_11 = (S) 2.63661358122e-6 + (S) 3.33765558362e-8 * x_sq;
+        const auto y_7_9_11 = (S) 0.000199027336899 + y_9_11 * x_sq;
+        const auto y_5_7_9_11 = (S) 0.00833223857843 + y_7_9_11 * x_sq;
+        const auto y_3_5_7_9_11 = (S) 0.166667159320 + y_5_7_9_11 * x_sq;
+        const auto y_1_3_5_7_9_11 = (S) 1 + y_3_5_7_9_11 * x_sq;
         return x * y_1_3_5_7_9_11;
     }
 
     template <typename T>
     T tanh_poly_9 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_7_9 = (T) 0.000192218110330 + (T) 3.54808622170e-6 * x_sq;
-        const auto y_5_7_9 = (T) 0.00834777254865 + y_7_9 * x_sq;
-        const auto y_3_5_7_9 = (T) 0.166658873283 + y_5_7_9 * x_sq;
-        const auto y_1_3_5_7_9 = (T) 1 + y_3_5_7_9 * x_sq;
+        const auto y_7_9 = (S) 0.000192218110330 + (S) 3.54808622170e-6 * x_sq;
+        const auto y_5_7_9 = (S) 0.00834777254865 + y_7_9 * x_sq;
+        const auto y_3_5_7_9 = (S) 0.166658873283 + y_5_7_9 * x_sq;
+        const auto y_1_3_5_7_9 = (S) 1 + y_3_5_7_9 * x_sq;
         return x * y_1_3_5_7_9;
     }
 
     template <typename T>
     T tanh_poly_7 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_5_7 = (T) 0.00818199927912 + (T) 0.000243153287690 * x_sq;
-        const auto y_3_5_7 = (T) 0.166769941467 + y_5_7 * x_sq;
-        const auto y_1_3_5_7 = (T) 1 + y_3_5_7 * x_sq;
+        const auto y_5_7 = (S) 0.00818199927912 + (S) 0.000243153287690 * x_sq;
+        const auto y_3_5_7 = (S) 0.166769941467 + y_5_7 * x_sq;
+        const auto y_1_3_5_7 = (S) 1 + y_3_5_7 * x_sq;
         return x * y_1_3_5_7;
     }
 
     template <typename T>
     T tanh_poly_5 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_3_5 = (T) 0.165326984031 + (T) 0.00970240200826 * x_sq;
-        const auto y_1_3_5 = (T) 1 + y_3_5 * x_sq;
+        const auto y_3_5 = (S) 0.165326984031 + (S) 0.00970240200826 * x_sq;
+        const auto y_1_3_5 = (S) 1 + y_3_5 * x_sq;
         return x * y_1_3_5;
     }
 
     template <typename T>
     T tanh_poly_3 (T x)
     {
+        using S = scalar_of_t<T>;
         const auto x_sq = x * x;
-        const auto y_1_3 = (T) 1 + (T) 0.183428244899 * x_sq;
+        const auto y_1_3 = (S) 1 + (S) 0.183428244899 * x_sq;
         return x * y_1_3;
     }
 } // namespace tanh_detail
@@ -76,6 +81,7 @@ T tanh (T x)
     else if constexpr (order == 3)
         x_poly = tanh_detail::tanh_poly_3 (x);
 
-    return x_poly * rsqrt (x_poly * x_poly + (T) 1);
+    using S = scalar_of_t<T>;
+    return x_poly * rsqrt (x_poly * x_poly + (S) 1);
 }
 } // namespace math_approx