Allow using different types for coordinates and values in {bi,tri}-linear interpolation functions (#3756)

* change {bi,tri}-linear interpolation functions so that a different type can be used for coordinates and values

* fixed bug

1 files changed, 19 insertions, 12 deletions

diff --git a/Source/Utils/Algorithms/LinearInterpolation.H b/Source/Utils/Algorithms/LinearInterpolation.H
index 32fdf7a6e..716c2d829 100644
--- a/Source/Utils/Algorithms/LinearInterpolation.H
+++ b/Source/Utils/Algorithms/LinearInterpolation.H
@@ -18,8 +18,11 @@ namespace utils::algorithms
      * Performs a linear interpolation at x given the 2 points
      * (x0, f0) and (x1, f1)
      */
-    template<typename T> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
-    T linear_interp(T x0, T x1, T f0, T f1, T x)
+    template<typename TCoord, typename TVal> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
+    constexpr auto linear_interp(
+        TCoord x0, TCoord x1,
+        TVal f0, TVal f1,
+        TCoord x)
     {
         return ((x1-x)*f0 + (x-x0)*f1)/(x1-x0);
     }
@@ -29,11 +32,14 @@ namespace utils::algorithms
      * Performs a bilinear interpolation at (x,y) given the 4 points
      * (x0, y0, f00), (x0, y1, f01), (x1, y0, f10), (x1, y1, f11).
      */
-    template<typename T> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
-    T bilinear_interp(T x0, T x1, T y0, T y1, T f00, T f01, T f10, T f11, T x, T y)
+    template<typename TCoord, typename TVal> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
+    constexpr auto bilinear_interp(
+        TCoord x0, TCoord x1, TCoord y0, TCoord y1,
+        TVal f00, TVal f01, TVal f10, TVal f11,
+        TCoord x, TCoord y)
     {
-        const T fx0 = linear_interp(x0, x1, f00, f10, x);
-        const T fx1 = linear_interp(x0, x1, f01, f11, x);
+        const auto fx0 = linear_interp(x0, x1, f00, f10, x);
+        const auto fx1 = linear_interp(x0, x1, f01, f11, x);
         return linear_interp(y0, y1, fx0, fx1, y);
     }
 
@@ -43,14 +49,15 @@ namespace utils::algorithms
      * (x0, y0, z0, f000), (x0, y0, z1, f001), (x0, y1, z0, f010), (x0, y1, z1, f011),
      * (x1, y0, z0, f100), (x1, y0, z1, f101), (x1, y1, z0, f110), (x1, y1, z1, f111)
      */
-    template<typename T> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
-    T trilinear_interp(T x0, T x1,T y0, T y1, T z0, T z1,
-        T f000, T f001, T f010, T f011, T f100, T f101, T f110, T f111,
-        T x, T y, T z)
+    template<typename TCoord, typename TVal> AMREX_GPU_DEVICE AMREX_FORCE_INLINE
+    constexpr auto trilinear_interp(
+        TCoord x0, TCoord x1, TCoord y0, TCoord y1, TCoord z0, TCoord z1,
+        TVal f000, TVal f001, TVal f010, TVal f011, TVal f100, TVal f101, TVal f110, TVal f111,
+        TCoord x, TCoord y, TCoord z)
     {
-        const T fxy0 = bilinear_interp(
+        const auto fxy0 = bilinear_interp(
             x0, x1, y0, y1, f000, f010, f100, f110, x, y);
-        const T fxy1 = bilinear_interp(
+        const auto fxy1 = bilinear_interp(
             x0, x1, y0, y1, f001, f011, f101, f111, x, y);
         return linear_interp(z0, z1, fxy0, fxy1, z);
     }