From 1ca92ead3136c7780141018c4f4102181af2ef7f Mon Sep 17 00:00:00 2001
From: Thomas Padioleau <thomas.padioleau@cea.fr>
Date: Thu, 19 Jun 2025 21:54:03 +0200
Subject: [PATCH 1/3] Add an assertion to the discrete_space function and a
 death test

---
 include/ddc/discrete_space.hpp | 18 ++++++++++++------
 tests/discrete_space.cpp       | 11 +++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/ddc/discrete_space.hpp b/include/ddc/discrete_space.hpp
index a380d3983..ad59169d0 100644
--- a/include/ddc/discrete_space.hpp
+++ b/include/ddc/discrete_space.hpp
@@ -212,6 +212,17 @@ std::tuple<Arg0, Arg1, Args...> init_discrete_space(std::tuple<DDimImpl, Arg0, A
     return detail::extract_after(std::move(a), std::index_sequence_for<Arg0, Arg1, Args...>());
 }
 
+/**
+ * @tparam DDim a discrete dimension
+ * @return a boolean indicating whether DDim is initialized.
+ * This function indicates whether a dimension is initialized.
+ */
+template <class DDim>
+bool is_discrete_space_initialized() noexcept
+{
+    return detail::g_discrete_space_dual<DDim>.has_value();
+}
+
 /**
  * @tparam DDim a discrete dimension
  * @return the discrete space instance associated with `DDim`.
@@ -222,6 +233,7 @@ template <class DDim, class MemorySpace = DDC_CURRENT_KOKKOS_SPACE>
 KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
 {
     if constexpr (std::is_same_v<MemorySpace, Kokkos::HostSpace>) {
+        assert(is_discrete_space_initialized<DDim>());
         return detail::g_discrete_space_dual<DDim>->get_host();
     }
 #if defined(KOKKOS_ENABLE_CUDA) || defined(KOKKOS_ENABLE_HIP)
@@ -238,12 +250,6 @@ KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
     }
 }
 
-template <class DDim>
-bool is_discrete_space_initialized() noexcept
-{
-    return detail::g_discrete_space_dual<DDim>.has_value();
-}
-
 template <class DDim>
 detail::ddim_impl_t<DDim, Kokkos::HostSpace> const& host_discrete_space()
 {
diff --git a/tests/discrete_space.cpp b/tests/discrete_space.cpp
index cbe8c3005..650fb02e3 100644
--- a/tests/discrete_space.cpp
+++ b/tests/discrete_space.cpp
@@ -24,3 +24,14 @@ TEST(DiscreteSpace, IsDiscreteSpaceInitialized)
             ddc::DiscreteVector<DDimX>(2)));
     EXPECT_TRUE(ddc::is_discrete_space_initialized<DDimX>());
 }
+
+TEST(DiscreteSpace, DiscreteSpace)
+{
+#if !defined(NDEBUG) // The assertion is only checked if NDEBUG isn't defined
+    EXPECT_DEATH(
+            ddc::discrete_space<DDimX>(),
+            R"rgx([Aa]ssert.*is_discrete_space_initialized<DDim>\(\))rgx");
+#else
+    GTEST_SKIP();
+#endif
+}

From b5a72c8e01fd8920b4158b0d14c6cabf42d86096 Mon Sep 17 00:00:00 2001
From: Thomas Padioleau <thomas.padioleau@cea.fr>
Date: Fri, 20 Jun 2025 14:46:16 +0200
Subject: [PATCH 2/3] Add comment and add a check for host_discrete_space

---
 include/ddc/discrete_space.hpp |  3 +++
 tests/discrete_space.cpp       | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/ddc/discrete_space.hpp b/include/ddc/discrete_space.hpp
index ad59169d0..320fe2818 100644
--- a/include/ddc/discrete_space.hpp
+++ b/include/ddc/discrete_space.hpp
@@ -232,6 +232,7 @@ bool is_discrete_space_initialized() noexcept
 template <class DDim, class MemorySpace = DDC_CURRENT_KOKKOS_SPACE>
 KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
 {
+    // Calling this function requires to call first `ddc::init_discrete_space<DDim>(...);`
     if constexpr (std::is_same_v<MemorySpace, Kokkos::HostSpace>) {
         assert(is_discrete_space_initialized<DDim>());
         return detail::g_discrete_space_dual<DDim>->get_host();
@@ -253,6 +254,8 @@ KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
 template <class DDim>
 detail::ddim_impl_t<DDim, Kokkos::HostSpace> const& host_discrete_space()
 {
+    // Calling this function requires to call first `ddc::init_discrete_space<DDim>(...);`
+    assert(is_discrete_space_initialized<DDim>());
     return detail::g_discrete_space_dual<DDim>->get_host();
 }
 
diff --git a/tests/discrete_space.cpp b/tests/discrete_space.cpp
index 650fb02e3..34c0b212b 100644
--- a/tests/discrete_space.cpp
+++ b/tests/discrete_space.cpp
@@ -25,6 +25,17 @@ TEST(DiscreteSpace, IsDiscreteSpaceInitialized)
     EXPECT_TRUE(ddc::is_discrete_space_initialized<DDimX>());
 }
 
+TEST(DiscreteSpace, HostDiscreteSpace)
+{
+#if !defined(NDEBUG) // The assertion is only checked if NDEBUG isn't defined
+    EXPECT_DEATH(
+            ddc::host_discrete_space<DDimX>(),
+            R"rgx([Aa]ssert.*is_discrete_space_initialized<DDim>\(\))rgx");
+#else
+    GTEST_SKIP();
+#endif
+}
+
 TEST(DiscreteSpace, DiscreteSpace)
 {
 #if !defined(NDEBUG) // The assertion is only checked if NDEBUG isn't defined

From 6584eaf57a507e907369e175d6d3669e466b5c50 Mon Sep 17 00:00:00 2001
From: Thomas Padioleau <thomas.padioleau@cea.fr>
Date: Fri, 20 Jun 2025 16:45:05 +0200
Subject: [PATCH 3/3] Apply suggestions from code review

Co-authored-by: Emily Bourne <louise.bourne@gmail.com>
---
 include/ddc/discrete_space.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/ddc/discrete_space.hpp b/include/ddc/discrete_space.hpp
index 320fe2818..8831b7fb6 100644
--- a/include/ddc/discrete_space.hpp
+++ b/include/ddc/discrete_space.hpp
@@ -232,7 +232,7 @@ bool is_discrete_space_initialized() noexcept
 template <class DDim, class MemorySpace = DDC_CURRENT_KOKKOS_SPACE>
 KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
 {
-    // Calling this function requires to call first `ddc::init_discrete_space<DDim>(...);`
+    // This function requires that `ddc::init_discrete_space<DDim>(...);` be called first
     if constexpr (std::is_same_v<MemorySpace, Kokkos::HostSpace>) {
         assert(is_discrete_space_initialized<DDim>());
         return detail::g_discrete_space_dual<DDim>->get_host();
@@ -254,7 +254,7 @@ KOKKOS_FUNCTION detail::ddim_impl_t<DDim, MemorySpace> const& discrete_space()
 template <class DDim>
 detail::ddim_impl_t<DDim, Kokkos::HostSpace> const& host_discrete_space()
 {
-    // Calling this function requires to call first `ddc::init_discrete_space<DDim>(...);`
+    // This function requires that `ddc::init_discrete_space<DDim>(...);` be called first
     assert(is_discrete_space_initialized<DDim>());
     return detail::g_discrete_space_dual<DDim>->get_host();
 }