From: Daniel Arndt <daniel.arndt@iwr.uni-heidelberg.de>
Date: Sat, 3 Nov 2018 12:52:23 +0000 (+0100)
Subject: Restrict access to ArrayView::operator[] to CPU memory
X-Git-Tag: v9.1.0-rc1~571^2~3
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2753e8efa9d2cdff7d1d07cce4c57d7ca1680c63;p=dealii.git

Restrict access to ArrayView::operator[] to CPU memory
---

diff --git a/include/deal.II/base/array_view.h b/include/deal.II/base/array_view.h
index 5c769608c4..19f0d9bd6a 100644
--- a/include/deal.II/base/array_view.h
+++ b/include/deal.II/base/array_view.h
@@ -34,15 +34,15 @@ DEAL_II_NAMESPACE_OPEN
 
 /**
  * A class that represents a window of memory locations of type @p ElementType
- * and presents it as if it was an array that can be accessed via an
- * <code>operator[]</code>. In essence, this class is nothing more than just a
- * pointer to the first location and an integer that represents the length of
- * the array in elements. The memory remains owned by whoever allocated it, as
- * this class does not take over ownership.
+ * and presents it as if it was an array. In essence, this class is nothing more
+ * than just a pointer to the first location and an integer that represents the
+ * length of the array in elements. The memory remains owned by whoever
+ * allocated it, as this class does not take over ownership.
  *
  * The advantage of using this class is that you don't have to pass around
  * pairs of pointers and that <code>operator[]</code> checks for the validity
- * of the index with which you subscript this array view.
+ * of the index with which you subscript this array view. Note that accessing
+ * elements is only allowed if the underlying data is stored in CPU memory.
  *
  * This class can handle views to both non-constant and constant memory
  * locations. If you want to represent a view of a constant array, then the
@@ -241,6 +241,9 @@ public:
    * <em>view object</em>. It may however return a reference to a non-@p const
    * memory location depending on whether the template type of the class is @p
    * const or not.
+   *
+   * This function is only allowed to be called if the underlying data is indeed
+   * stored in CPU memory.
    */
   value_type &operator[](const std::size_t i) const;
 
@@ -488,6 +491,10 @@ template <typename ElementType, typename MemorySpaceType>
 inline typename ArrayView<ElementType, MemorySpaceType>::value_type &
   ArrayView<ElementType, MemorySpaceType>::operator[](const std::size_t i) const
 {
+  Assert(
+    (std::is_same<MemorySpaceType, MemorySpace::Host>::value),
+    ExcMessage(
+      "Accessing elements is only allowed if the data is stored in CPU memory!"));
   Assert(i < n_elements, ExcIndexRange(i, 0, n_elements));
 
   return *(starting_element + i);
diff --git a/tests/cuda/array_view_access_data.cu b/tests/cuda/array_view_access_data.cu
new file mode 100644
index 0000000000..5165c22b5f
--- /dev/null
+++ b/tests/cuda/array_view_access_data.cu
@@ -0,0 +1,46 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2018 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// ---------------------------------------------------------------------
+
+
+// check that we detect that accessing CUDA memory in an ArrayView object
+// is not allowed.
+
+#include <deal.II/base/array_view.h>
+
+#include "../tests.h"
+
+int
+main(int argc, char **argv)
+{
+  deal_II_exceptions::disable_abort_on_exception();
+
+  initlog();
+
+  std::unique_ptr<unsigned int[], void (*)(unsigned int *)> dummy_cuda(
+    Utilities::CUDA::allocate_device_data<unsigned int>(2),
+    Utilities::CUDA::delete_device_data<unsigned int>);
+
+  try
+    {
+      ArrayView<unsigned int, MemorySpace::CUDA> view(dummy_cuda.get(), 2);
+      const auto                                 dummy = view[0];
+    }
+  catch (const ExceptionBase &exc)
+    {
+      deallog << exc.what() << std::endl;
+    }
+
+  return 0;
+}
diff --git a/tests/cuda/array_view_access_data.debug.output b/tests/cuda/array_view_access_data.debug.output
new file mode 100644
index 0000000000..b50cbe5806
--- /dev/null
+++ b/tests/cuda/array_view_access_data.debug.output
@@ -0,0 +1,11 @@
+
+DEAL::
+--------------------------------------------------------
+An error occurred in file <array_view.h> in function
+    dealii::ArrayView<ElementType, MemorySpaceType>::value_type& dealii::ArrayView<ElementType, MemorySpaceType>::operator[](std::size_t) const [with ElementType = unsigned int; MemorySpaceType = dealii::MemorySpace::CUDA; dealii::ArrayView<ElementType, MemorySpaceType>::value_type = unsigned int; std::size_t = long unsigned int]
+The violated condition was: 
+    (std::is_same<MemorySpaceType, MemorySpace::Host>::value)
+Additional information: 
+    Accessing elements is only allowed if the data is stored in CPU memory!
+--------------------------------------------------------
+