From 367e7ccd8d87e449d3072e35433e75c5916fad0f Mon Sep 17 00:00:00 2001
From: Thomas Padioleau <thomas.padioleau@cea.fr>
Date: Tue, 5 Nov 2024 13:30:47 +0100
Subject: [PATCH] Pass views by const& in fftshift (#192)

* Pass views by const& in fftshift

* Review from yasahi-hpc

Co-authored-by: yasahi-hpc <57478230+yasahi-hpc@users.noreply.github.com>

---------

Co-authored-by: yasahi-hpc <57478230+yasahi-hpc@users.noreply.github.com>
---
 common/src/KokkosFFT_Helpers.hpp | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/common/src/KokkosFFT_Helpers.hpp b/common/src/KokkosFFT_Helpers.hpp
index f3e06b4..7b06aa5 100644
--- a/common/src/KokkosFFT_Helpers.hpp
+++ b/common/src/KokkosFFT_Helpers.hpp
@@ -39,8 +39,8 @@ auto get_shift(const ViewType& inout, axis_type<DIM> axes, int direction = 1) {
 }
 
 template <typename ExecutionSpace, typename ViewType>
-void roll(const ExecutionSpace& exec_space, ViewType& inout, axis_type<1> shift,
-          axis_type<1>) {
+void roll(const ExecutionSpace& exec_space, const ViewType& inout,
+          axis_type<1> shift, axis_type<1> /* axes */) {
   // Last parameter is ignored but present for keeping the interface consistent
   static_assert(ViewType::rank() == 1, "roll: Rank of View must be 1.");
   int n0 = inout.extent_int(0);
@@ -67,13 +67,13 @@ void roll(const ExecutionSpace& exec_space, ViewType& inout, axis_type<1> shift,
           }
         });
 
-    inout = tmp;
+    Kokkos::deep_copy(inout, tmp);
   }
 }
 
 template <typename ExecutionSpace, typename ViewType, std::size_t DIM1 = 1>
-void roll(const ExecutionSpace& exec_space, ViewType& inout, axis_type<2> shift,
-          axis_type<DIM1> axes) {
+void roll(const ExecutionSpace& exec_space, const ViewType& inout,
+          axis_type<2> shift, axis_type<DIM1> axes) {
   constexpr int DIM0 = 2;
   static_assert(ViewType::rank() == DIM0, "roll: Rank of View must be 2.");
   int n0 = inout.extent_int(0), n1 = inout.extent_int(1);
@@ -128,18 +128,18 @@ void roll(const ExecutionSpace& exec_space, ViewType& inout, axis_type<2> shift,
         }
       });
 
-  inout = tmp;
+  Kokkos::deep_copy(inout, tmp);
 }
 
 template <typename ExecutionSpace, typename ViewType, std::size_t DIM = 1>
-void fftshift_impl(const ExecutionSpace& exec_space, ViewType& inout,
+void fftshift_impl(const ExecutionSpace& exec_space, const ViewType& inout,
                    axis_type<DIM> axes) {
   auto shift = get_shift(inout, axes);
   roll(exec_space, inout, shift, axes);
 }
 
 template <typename ExecutionSpace, typename ViewType, std::size_t DIM = 1>
-void ifftshift_impl(const ExecutionSpace& exec_space, ViewType& inout,
+void ifftshift_impl(const ExecutionSpace& exec_space, const ViewType& inout,
                     axis_type<DIM> axes) {
   auto shift = get_shift(inout, axes, -1);
   roll(exec_space, inout, shift, axes);
@@ -219,7 +219,7 @@ auto rfftfreq(const ExecutionSpace&, const std::size_t n,
 /// \param axes [in] Axes over which to shift (default: nullopt, shifting over
 /// all axes)
 template <typename ExecutionSpace, typename ViewType>
-void fftshift(const ExecutionSpace& exec_space, ViewType& inout,
+void fftshift(const ExecutionSpace& exec_space, const ViewType& inout,
               std::optional<int> axes = std::nullopt) {
   static_assert(KokkosFFT::Impl::is_operatable_view_v<ExecutionSpace, ViewType>,
                 "fftshift: View value type must be float, double, "
@@ -246,7 +246,7 @@ void fftshift(const ExecutionSpace& exec_space, ViewType& inout,
 /// \param inout [in,out] Spectrum
 /// \param axes [in] Axes over which to shift
 template <typename ExecutionSpace, typename ViewType, std::size_t DIM = 1>
-void fftshift(const ExecutionSpace& exec_space, ViewType& inout,
+void fftshift(const ExecutionSpace& exec_space, const ViewType& inout,
               axis_type<DIM> axes) {
   static_assert(KokkosFFT::Impl::is_operatable_view_v<ExecutionSpace, ViewType>,
                 "fftshift: View value type must be float, double, "
@@ -269,7 +269,7 @@ void fftshift(const ExecutionSpace& exec_space, ViewType& inout,
 /// \param axes [in] Axes over which to shift (default: nullopt, shifting over
 /// all axes)
 template <typename ExecutionSpace, typename ViewType>
-void ifftshift(const ExecutionSpace& exec_space, ViewType& inout,
+void ifftshift(const ExecutionSpace& exec_space, const ViewType& inout,
                std::optional<int> axes = std::nullopt) {
   static_assert(KokkosFFT::Impl::is_operatable_view_v<ExecutionSpace, ViewType>,
                 "ifftshift: View value type must be float, double, "
@@ -295,7 +295,7 @@ void ifftshift(const ExecutionSpace& exec_space, ViewType& inout,
 /// \param inout [in,out] Spectrum
 /// \param axes [in] Axes over which to shift
 template <typename ExecutionSpace, typename ViewType, std::size_t DIM = 1>
-void ifftshift(const ExecutionSpace& exec_space, ViewType& inout,
+void ifftshift(const ExecutionSpace& exec_space, const ViewType& inout,
                axis_type<DIM> axes) {
   static_assert(KokkosFFT::Impl::is_operatable_view_v<ExecutionSpace, ViewType>,
                 "ifftshift: View value type must be float, double, "