Support printing a layout stride (#1134)

Author: tpadioleau

src/ddc/create_mirror.hpp

@@ -13,6 +13,33 @@
 
 namespace ddc {
 
+namespace detail {
+
+/**
+ * @brief Ensure a layout_right view of a ChunkSpan, copying if necessary.
+ *
+ * If the input `src` already uses `Kokkos::layout_right`, it is returned as-is.
+ * Otherwise, a new chunk with layout_right is allocated and a deep copy of
+ * `src` is performed into it.
+ *
+ * @param[in] src Source ChunkSpan to adapt.
+ * @return Either the original view (if already LayoutRight) or a copied chunk.
+ */
+template <class ElementType, class Support, class Layout, class MemorySpace>
+auto create_layout_right_view_and_copy(
+        ChunkSpan<ElementType, Support, Layout, MemorySpace> const& src)
+{
+    if constexpr (std::is_same_v<Layout, Kokkos::layout_right>) {
+        return src;
+    } else {
+        Chunk chunk(src.domain(), KokkosAllocator<std::remove_const_t<ElementType>, MemorySpace>());
+        parallel_deepcopy(chunk, src);
+        return chunk;
+    }
+}
+
+} // namespace detail
+
 /// @param[in] space A Kokkos memory space or execution space.
 /// @param[in] src A layout right ChunkSpan.
 /// @return a `Chunk` with the same support and layout as `src` allocated on the `Space::memory_space` memory space.

src/ddc/print.hpp

@@ -18,6 +18,7 @@
 #include <Kokkos_Core.hpp>
 
 #include "chunk_span.hpp"
+#include "create_mirror.hpp"
 #include "discrete_vector.hpp"
 
 namespace ddc {
@@ -350,13 +351,16 @@ std::ostream& print_content(
         std::ostream& os,
         ChunkSpan<ElementType, SupportType, LayoutStridedPolicy, MemorySpace> const& chunk_span)
 {
-    auto h_chunk_span = create_mirror_view_and_copy(Kokkos::HostSpace(), chunk_span);
+    auto chunk_span_right = detail::create_layout_right_view_and_copy(chunk_span);
+    auto chunk_span_right_host
+            = create_mirror_view_and_copy(Kokkos::HostSpace(), chunk_span_right.span_view());
 
-    using chunkspan_type = std::remove_cv_t<std::remove_reference_t<decltype(h_chunk_span)>>;
+    using chunkspan_type
+            = std::remove_cv_t<std::remove_reference_t<decltype(chunk_span_right_host)>>;
     using mdspan_type = chunkspan_type::allocation_mdspan_type;
     using extents = mdspan_type::extents_type;
 
-    mdspan_type const allocated_mdspan = h_chunk_span.allocation_mdspan();
+    mdspan_type const allocated_mdspan = chunk_span_right_host.allocation_mdspan();
 
     ddc::detail::ChunkPrinter& printer = ddc::detail::ChunkPrinter::get_instance();
     std::scoped_lock const lock(printer.m_global_lock);

tests/print.cpp

@@ -496,6 +496,16 @@ void TestPrintTestCheckOutput3d()
                 "  [0.12345 0.12345 0.12345]\n"
                 "  [0.12345 0.12345 0.12345]]]");
     }
+
+    {
+        ddc::ChunkSpan const sub_chunk_span = chunk_span[domain_1.front()][domain_2.front()];
+        ASSERT_TRUE((std::is_same_v<
+                     typename decltype(sub_chunk_span)::layout_type,
+                     Kokkos::layout_stride>));
+        std::stringstream ss;
+        print_content(ss, sub_chunk_span);
+        EXPECT_EQ(ss.str(), "[0.12345 0.12345 0.12345]");
+    }
 }
 
 TEST(Print, CheckOutput3d)