Port alpaka phi functions to DataFormats

Author: VourMa

DataFormats/Math/interface/alpaka/deltaPhi.h

@@ -0,0 +1,35 @@
+#ifndef DataFormats_Math_alpaka_deltaPhi_h
+#define DataFormats_Math_alpaka_deltaPhi_h
+
+#include "HeterogeneousCore/AlpakaInterface/interface/config.h"
+
+namespace cms::alpakatools {
+
+  // reduce to [-pi,pi]
+  template <typename TAcc, typename T>
+  ALPAKA_FN_HOST_ACC ALPAKA_FN_INLINE constexpr T reduceRange(TAcc const& acc, T x) {
+    constexpr T o2pi = 1. / (2. * M_PI);
+    if (alpaka::math::abs(acc, x) <= T(M_PI))
+      return x;
+    T n = alpaka::math::round(acc, x * o2pi);
+    return x - n * T(2. * M_PI);
+  }
+
+  template <typename TAcc, typename T>
+  ALPAKA_FN_HOST_ACC ALPAKA_FN_INLINE constexpr T phi(TAcc const& acc, T x, T y) {
+    return reduceRange(acc, M_PI + alpaka::math::atan2(acc, -y, -x));
+  }
+
+  template <typename TAcc, typename T>
+  ALPAKA_FN_HOST_ACC ALPAKA_FN_INLINE constexpr T deltaPhi(TAcc const& acc, T x1, T y1, T x2, T y2) {
+    return reduceRange(acc, alpaka::math::atan2(acc, -y2, -x2) - alpaka::math::atan2(acc, -y1, -x1));
+  }
+
+  template <typename TAcc, typename T>
+  ALPAKA_FN_HOST_ACC ALPAKA_FN_INLINE constexpr T deltaPhi(T phi1, T phi2) {
+    return reduceRange(phi1 - phi2);
+  }
+
+}  // namespace cms::alpakatools
+
+#endif