From 7adf0bda0009f240ec19efbc1721c9e4cabb6333 Mon Sep 17 00:00:00 2001
From: Yuuichi Asahi <y.asahi@nr.titech.ac.jp>
Date: Thu, 12 Sep 2024 17:37:12 +0900
Subject: [PATCH] Add an example to generate compile time errors

---
 examples/08_awful_usage/08_awful_usage.cpp | 80 ++++++++++++++++++++++
 examples/08_awful_usage/CMakeLists.txt     |  6 ++
 examples/CMakeLists.txt                    |  1 +
 3 files changed, 87 insertions(+)
 create mode 100644 examples/08_awful_usage/08_awful_usage.cpp
 create mode 100644 examples/08_awful_usage/CMakeLists.txt

diff --git a/examples/08_awful_usage/08_awful_usage.cpp b/examples/08_awful_usage/08_awful_usage.cpp
new file mode 100644
index 00000000..c08b57e6
--- /dev/null
+++ b/examples/08_awful_usage/08_awful_usage.cpp
@@ -0,0 +1,80 @@
+// SPDX-FileCopyrightText: (C) The Kokkos-FFT development team, see COPYRIGHT.md file
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+
+#include <Kokkos_Core.hpp>
+#include <Kokkos_Complex.hpp>
+#include <Kokkos_Random.hpp>
+#include <KokkosFFT.hpp>
+
+using execution_space = Kokkos::DefaultExecutionSpace;
+template <typename T>
+using View1D = Kokkos::View<T*, execution_space>;
+
+template <typename T>
+using View2D = Kokkos::View<T**, execution_space>;
+
+template <typename T>
+using View3D = Kokkos::View<T***, execution_space>;
+
+template <std::size_t DIM>
+using axis_type = KokkosFFT::axis_type<DIM>;
+template <std::size_t DIM>
+using shape_type = KokkosFFT::shape_type<DIM>;
+
+int main(int argc, char* argv[]) {
+  Kokkos::initialize(argc, argv);
+  {
+    constexpr int n0 = 128, n1 = 128, n2 = 16;
+    const Kokkos::complex<double> I(1.0, 1.0);
+
+    shape_type<3> shape;
+    shape[0] = n0;
+    shape[1] = n1;
+    shape[2] = n2;
+
+    View1D<Kokkos::complex<double> > xc("xc", n0);
+    View2D<Kokkos::complex<double> > xc2("xc2", n0, n1);
+    View1D<double> xr("xr", n0);
+    View2D<double> xr2("xr2", n0, n1);
+
+    Kokkos::Random_XorShift64_Pool<> random_pool(12345);
+    execution_space exec;
+    Kokkos::fill_random(exec, xc, random_pool, I);
+    exec.fence();
+
+#if 0
+    // Compilte time error for inconsistent types
+    // You will get the following compilation errors if you uncomment this block
+    // error: static assertion failed with "rfft: InViewType must be real"
+    // error: static assertion failed with "rfft: OutViewType must be complex"
+    KokkosFFT::rfft(exec, xc, xr); // Incorrect, input is complex and output is real
+    KokkosFFT::rfft(exec, xr, xc); // Correct, input is real and output is complex
+#endif
+
+#if 0
+    // Compilte time error if FFT rank > View rank (2D FFT on 1D View)
+    // You will get the following compilation errors if you uncomment this block
+    // error: static assertion failed with "rfft2: View rank must be larger than or equal to 2"
+    KokkosFFT::rfft2(exec, xr, xc); // Incorrect, input and output are 1D Views
+    KokkosFFT::rfft2(exec, xr2, xc2); // Correct, input and output are 2D Views
+#endif
+
+#if 0
+    // Compilte time error if FFT plan and execution is inconsistent
+    // You will get the following compilation errors if you uncomment this block
+    // error: static assertion failed with "Plan::good: InViewType for plan and execution are not identical."
+    // error: static assertion failed with "Plan::good: OutViewType for plan and execution are not identical."
+    int axis = -1;
+    KokkosFFT::Impl::Plan rfft_plan(exec, xr, xc,
+                                    KokkosFFT::Direction::forward, axis);
+    KokkosFFT::Impl::fft_exec_impl(rfft_plan, xc, xr); // Incorrect, input and output are reversed
+    KokkosFFT::Impl::fft_exec_impl(rfft_plan, xr, xc); // Correct, same input and output
+#endif
+
+    exec.fence();
+  }
+  Kokkos::finalize();
+
+  return 0;
+}
diff --git a/examples/08_awful_usage/CMakeLists.txt b/examples/08_awful_usage/CMakeLists.txt
new file mode 100644
index 00000000..5949ebdf
--- /dev/null
+++ b/examples/08_awful_usage/CMakeLists.txt
@@ -0,0 +1,6 @@
+# SPDX-FileCopyrightText: (C) The Kokkos-FFT development team, see COPYRIGHT.md file
+#
+# SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+
+add_executable(08_awful_usage 08_awful_usage.cpp)
+target_link_libraries(08_awful_usage PUBLIC KokkosFFT::fft)
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index f587f4c2..27704f63 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -9,3 +9,4 @@ add_subdirectory(04_batchedFFT)
 add_subdirectory(05_1DFFT_HOST_DEVICE)
 add_subdirectory(06_1DFFT_reuse_plans)
 add_subdirectory(07_unmanaged_views)
+add_subdirectory(08_awful_usage)