From 7a6946c2555f535d7ae80c25c51c6a4bc939456b Mon Sep 17 00:00:00 2001
From: Yuuichi Asahi <y.asahi@nr.titech.ac.jp>
Date: Tue, 17 Dec 2024 22:21:29 +0900
Subject: [PATCH] update host backend based on revies

---
 fft/src/KokkosFFT_FFTW_Types.hpp     | 50 ++++++++++++++++------------
 fft/src/KokkosFFT_Host_transform.hpp |  1 +
 fft/src/KokkosFFT_Host_types.hpp     |  2 +-
 fft/src/KokkosFFT_Plans.hpp          |  2 +-
 4 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/fft/src/KokkosFFT_FFTW_Types.hpp b/fft/src/KokkosFFT_FFTW_Types.hpp
index d519aff6..0e0bd43e 100644
--- a/fft/src/KokkosFFT_FFTW_Types.hpp
+++ b/fft/src/KokkosFFT_FFTW_Types.hpp
@@ -23,14 +23,14 @@ namespace Impl {
 enum class FFTWTransformType { R2C, D2Z, C2R, Z2D, C2C, Z2Z };
 
 // Define fft transform types
-template <typename ExecutionSpace, typename T1, typename T2>
+template <typename T1, typename T2>
 struct fftw_transform_type {
   static_assert(std::is_same_v<T1, T2>,
                 "Real to real transform is unavailable");
 };
 
-template <typename ExecutionSpace, typename T1, typename T2>
-struct fftw_transform_type<ExecutionSpace, T1, Kokkos::complex<T2>> {
+template <typename T1, typename T2>
+struct fftw_transform_type<T1, Kokkos::complex<T2>> {
   static_assert(std::is_same_v<T1, T2>,
                 "T1 and T2 should have the same precision");
   static constexpr FFTWTransformType m_type = std::is_same_v<T1, float>
@@ -39,8 +39,8 @@ struct fftw_transform_type<ExecutionSpace, T1, Kokkos::complex<T2>> {
   static constexpr FFTWTransformType type() { return m_type; };
 };
 
-template <typename ExecutionSpace, typename T1, typename T2>
-struct fftw_transform_type<ExecutionSpace, Kokkos::complex<T1>, T2> {
+template <typename T1, typename T2>
+struct fftw_transform_type<Kokkos::complex<T1>, T2> {
   static_assert(std::is_same_v<T1, T2>,
                 "T1 and T2 should have the same precision");
   static constexpr FFTWTransformType m_type = std::is_same_v<T2, float>
@@ -49,9 +49,8 @@ struct fftw_transform_type<ExecutionSpace, Kokkos::complex<T1>, T2> {
   static constexpr FFTWTransformType type() { return m_type; };
 };
 
-template <typename ExecutionSpace, typename T1, typename T2>
-struct fftw_transform_type<ExecutionSpace, Kokkos::complex<T1>,
-                           Kokkos::complex<T2>> {
+template <typename T1, typename T2>
+struct fftw_transform_type<Kokkos::complex<T1>, Kokkos::complex<T2>> {
   static_assert(std::is_same_v<T1, T2>,
                 "T1 and T2 should have the same precision");
   static constexpr FFTWTransformType m_type = std::is_same_v<T1, float>
@@ -78,7 +77,7 @@ struct ScopedFFTWPlan {
                  int idist, OutScalarType *out, const int *onembed, int ostride,
                  int odist, [[maybe_unused]] int sign, unsigned flags) {
     init_threads(exec_space);
-    constexpr auto type = fftw_transform_type<ExecutionSpace, T1, T2>::type();
+    constexpr auto type = fftw_transform_type<T1, T2>::type();
     if constexpr (type == KokkosFFT::Impl::FFTWTransformType::R2C) {
       m_plan =
           fftwf_plan_many_dft_r2c(rank, n, howmany, in, inembed, istride, idist,
@@ -105,6 +104,7 @@ struct ScopedFFTWPlan {
     }
     m_is_created = true;
   }
+
   ~ScopedFFTWPlan() noexcept {
     cleanup_threads();
     if constexpr (std::is_same_v<plan_type, fftwf_plan>) {
@@ -120,29 +120,35 @@ struct ScopedFFTWPlan {
   ScopedFFTWPlan &operator=(ScopedFFTWPlan &&)      = delete;
   ScopedFFTWPlan(ScopedFFTWPlan &&)                 = delete;
 
-  const plan_type &plan() const { return m_plan; }
+  plan_type plan() const noexcept { return m_plan; }
 
  private:
   void init_threads([[maybe_unused]] const ExecutionSpace &exec_space) {
 #if defined(KOKKOS_ENABLE_OPENMP) || defined(KOKKOS_ENABLE_THREADS)
-    int nthreads = exec_space.concurrency();
-
-    if constexpr (std::is_same_v<plan_type, fftwf_plan>) {
-      fftwf_init_threads();
-      fftwf_plan_with_nthreads(nthreads);
-    } else {
-      fftw_init_threads();
-      fftw_plan_with_nthreads(nthreads);
+    if constexpr (std::is_same_v<ExecutionSpace,
+                                 Kokkos::DefaultHostExecutionSpace>) {
+      int nthreads = exec_space.concurrency();
+
+      if constexpr (std::is_same_v<plan_type, fftwf_plan>) {
+        fftwf_init_threads();
+        fftwf_plan_with_nthreads(nthreads);
+      } else {
+        fftw_init_threads();
+        fftw_plan_with_nthreads(nthreads);
+      }
     }
 #endif
   }
 
   void cleanup_threads() {
 #if defined(KOKKOS_ENABLE_OPENMP) || defined(KOKKOS_ENABLE_THREADS)
-    if constexpr (std::is_same_v<plan_type, fftwf_plan>) {
-      fftwf_cleanup_threads();
-    } else {
-      fftw_cleanup_threads();
+    if constexpr (std::is_same_v<ExecutionSpace,
+                                 Kokkos::DefaultHostExecutionSpace>) {
+      if constexpr (std::is_same_v<plan_type, fftwf_plan>) {
+        fftwf_cleanup_threads();
+      } else {
+        fftw_cleanup_threads();
+      }
     }
 #endif
   }
diff --git a/fft/src/KokkosFFT_Host_transform.hpp b/fft/src/KokkosFFT_Host_transform.hpp
index 6aeabb1a..5113acde 100644
--- a/fft/src/KokkosFFT_Host_transform.hpp
+++ b/fft/src/KokkosFFT_Host_transform.hpp
@@ -9,6 +9,7 @@
 
 namespace KokkosFFT {
 namespace Impl {
+
 template <typename ScopedPlanType>
 void exec_plan(ScopedPlanType& scoped_plan, float* idata, fftwf_complex* odata,
                int /*direction*/) {
diff --git a/fft/src/KokkosFFT_Host_types.hpp b/fft/src/KokkosFFT_Host_types.hpp
index 6d438a0c..85e754b2 100644
--- a/fft/src/KokkosFFT_Host_types.hpp
+++ b/fft/src/KokkosFFT_Host_types.hpp
@@ -23,7 +23,7 @@ template <typename ExecutionSpace>
 using TransformType = FFTWTransformType;
 
 template <typename ExecutionSpace, typename T1, typename T2>
-using transform_type = fftw_transform_type<ExecutionSpace, T1, T2>;
+using transform_type = fftw_transform_type<T1, T2>;
 
 template <typename ExecutionSpace, typename T1, typename T2>
 struct FFTPlanType {
diff --git a/fft/src/KokkosFFT_Plans.hpp b/fft/src/KokkosFFT_Plans.hpp
index 1ce815c5..7f6b98af 100644
--- a/fft/src/KokkosFFT_Plans.hpp
+++ b/fft/src/KokkosFFT_Plans.hpp
@@ -264,7 +264,7 @@ class Plan {
                                               direction, axes, s, m_is_inplace);
   }
 
-  ~Plan() {}
+  ~Plan() noexcept = default;
 
   Plan()                       = delete;
   Plan(const Plan&)            = delete;