Merge branch 'aligned_vector.CxxUtils-20200302' into 'master'

CxxUtils: Add aligned_vector.

See merge request atlas/athena!30798

Control/CxxUtils/CMakeLists.txt

@@ -111,7 +111,7 @@ foreach( test sincos_test copyif_test ArrayScanner_test Arrayrep_test
       CachedValue_test CachedPointer_test CachedUniquePtr_test
       atomic_fetch_minmax_test
       MurmurHash2_test bitmask_test crc64_test Ring_test
-      restrict_test vectorize_test get_unaligned_test )
+      restrict_test vectorize_test get_unaligned_test aligned_vector_test )
    atlas_add_test( ${test}
       SOURCES test/${test}.cxx
       LOG_IGNORE_PATTERN "no version information available"

Control/CxxUtils/CxxUtils/aligned_vector.h

+// This file's extension implies that it's C, but it's really -*- C++ -*-.
+/*
+ * Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration.
+ */
+/**
+ * @file CxxUtils/aligned_vector.h
+ * @author scott snyder <snyder@bnl.gov>
+ * @date Feb, 2020
+ * @brief @c std::vector with extra alignment.
+ *
+ * The payload of a @c std::vector<T> is aligned appropriately for @c T.
+ * However, there are some times when one would like to force a larger
+ * alignment, for example if the vector is being used to hold data
+ * to be processed with vector instructions.  @c aligned_vector
+ * defined here is a @c std::vector with higher alignment.
+ * @c vec_aligned_vector is a vector that should be sufficiently
+ * aligned for any vector instructions on this platform.
+ */
+
+
+#ifndef CXXUTILS_ALIGNED_VECTOR_H
+#define CXXUTILS_ALIGNED_VECTOR_H
+
+
+#include "boost/align/aligned_allocator.hpp"
+#include <vector>
+
+
+namespace CxxUtils {
+
+
+/**
+ * @brief A @c std::vector with extra alignment.
+ *
+ * The alignment for the payload will be at least either that required by @c T
+ * or @c Alignment, whichever is greater.
+ */
+template <class T, size_t Alignment=1>
+using aligned_vector = std::vector<T, boost::alignment::aligned_allocator<T, Alignment> >;
+
+
+/**
+ * @brief A @c std::vector with alignment sufficienct for any vector
+ *        instructions on this platform.
+ *
+ * For now, just hardcode 64, which is sufficient for a 512-bit vector,
+ * the largest supported by any x86 processors.  We may want to make this
+ * platform-dependent in the future.
+ */
+template <class T>
+using vec_aligned_vector = aligned_vector<T, 64>;
+
+
+} // namespace CxxUtils
+
+
+#endif // not CXXUTILS_ALIGNED_VECTOR_H

Control/CxxUtils/share/aligned_vector_test.ref

+test1

Control/CxxUtils/test/aligned_vector_test.cxx

+/*
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
+*/
+/**
+ * @file CxxUtils/test/aligned_vector_test.cxx
+ * @author scott snyder <snyder@bnl.gov>
+ * @date Feb, 2020
+ * @brief Unit test for aligned_vector.
+ */
+
+
+#undef NDEBUG
+#include "CxxUtils/aligned_vector.h"
+#include <cassert>
+#include <iostream>
+
+
+template <size_t N>
+void testone()
+{
+  std::vector<CxxUtils::aligned_vector<float, N> > v;
+  v.resize (10);
+  for (auto& vv : v) {
+    vv.resize (10);
+    assert ((reinterpret_cast<unsigned long>(vv.data()) & (N-1)) == 0);
+  }
+}
+
+
+void test1()
+{
+  std::cout << "test1\n";
+  testone<4>();
+  testone<8>();
+  testone<16>();
+  testone<32>();
+  testone<64>();
+  testone<128>();
+  testone<256>();
+  testone<512>();
+  testone<1024>();
+  testone<2048>();
+  testone<4096>();
+  testone<8192>();
+  testone<16384>();
+  testone<32768>();
+  testone<65536>();
+}
+
+
+int main()
+{
+  test1();
+  return 0;
+}
+