Start on memory utility

Author: schnellerhase

cpp/dolfinx/common/memory.h

@@ -0,0 +1,48 @@
+// Copyright (C) 2025 Paul T. Kühner
+//
+// This file is part of DOLFINx (https://www.fenicsproject.org)
+//
+// SPDX-License-Identifier:    LGPL-3.0-or-later
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+namespace dolfinx::common
+{
+
+namespace impl
+{
+
+template <typename T>
+std::size_t memory(const T& obj)
+{
+  static_assert(false, "Memory usage not supported for provided type.");
+}
+
+template <typename T>
+std::size_t memory(const std::vector<T>& vec)
+{
+  using value_type = typename std::vector<T>::value_type;
+
+  std::size_t size_type = sizeof(vec);
+  std::size_t size_data = vec.capacity() * sizeof(value_type);
+  return size_type + size_data;
+}
+
+} // namespace impl
+
+constexpr std::int64_t byte = 1;
+constexpr std::int64_t kilobyte = 1024;
+constexpr std::int64_t megabyte = 1'048'576;
+constexpr std::int64_t gigabyte = 1'073'741'824;
+constexpr std::int64_t terabyte = 1'099'511'627'776;
+
+template <typename T>
+double memory(const T& obj, std::int64_t bytes_per_unit = byte)
+{
+  std::size_t bytes = impl::memory(obj);
+  return static_cast<double>(bytes) / bytes_per_unit;
+}
+
+} // namespace dolfinx::common

cpp/test/CMakeLists.txt

@@ -38,6 +38,7 @@ add_executable(
   common/CIFailure.cpp
   common/sub_systems_manager.cpp
   common/index_map.cpp
+  common/memory.cpp
   common/sort.cpp
   fem/form.cpp
   fem/functionspace.cpp

cpp/test/common/memory.cpp

@@ -0,0 +1,29 @@
+// Copyright (C) 2025 Paul T. Kühner
+//
+// This file is part of DOLFINx (https://www.fenicsproject.org)
+//
+// SPDX-License-Identifier:    LGPL-3.0-or-later
+
+#include <catch2/catch_approx.hpp>
+#include <catch2/catch_template_test_macros.hpp>
+#include <catch2/catch_test_macros.hpp>
+
+#include <complex>
+#include <vector>
+
+#include "dolfinx/common/memory.h"
+
+using namespace dolfinx::common;
+
+TEMPLATE_TEST_CASE("memory-vector", "[memory]", std::int16_t, std::int32_t,
+                   std::int64_t, std::uint16_t, std::uint32_t, std::uint64_t,
+                   float, double, std::complex<float>, std::complex<double>)
+{
+  std::vector<TestType> v;
+  v.reserve(10);
+
+  std::size_t bytes = sizeof(std::vector<TestType>) + 10 * sizeof(TestType);
+
+  for (auto unit : {byte, kilobyte, megabyte, gigabyte, terabyte})
+    CHECK(memory(v, unit) == Catch::Approx(static_cast<double>(bytes) / unit));
+}