src/gromacs/utility/defaultinitializationallocator.h

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
   3  *
   4  * Copyright (c) 2019, by the GROMACS development team, led by
   5  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
   6  * and including many others, as listed in the AUTHORS file in the
   7  * top-level source directory and at http://www.gromacs.org.
   8  *
   9  * GROMACS is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public License
  11  * as published by the Free Software Foundation; either version 2.1
  12  * of the License, or (at your option) any later version.
  13  *
  14  * GROMACS is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with GROMACS; if not, see
  21  * http://www.gnu.org/licenses, or write to the Free Software Foundation,
  22  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
  23  *
  24  * If you want to redistribute modifications to GROMACS, please
  25  * consider that scientific software is very special. Version
  26  * control is crucial - bugs must be traceable. We will be happy to
  27  * consider code for inclusion in the official distribution, but
  28  * derived work must not be called official GROMACS. Details are found
  29  * in the README & COPYING files - if they are missing, get the
  30  * official version at http://www.gromacs.org.
  31  *
  32  * To help us fund GROMACS development, we humbly ask that you cite
  33  * the research papers on the package. Check out http://www.gromacs.org.
  34  */
  35 /*! \libinternal \file
  36  * \brief Declares an allocator that can use default initialization instead
  37  * of values initialization. This is useful for improving performance of
  38  * resize() in standard vectors for buffers in performance critical code.
  39  *
  40  * \author Berk Hess <hess@kth.se>
  41  * \inlibraryapi
  42  * \ingroup module_utility
  43  */
  44 #ifndef GMX_UTILITY_DEFAULTINITIALIZATIONALLOCATOR_H
  45 #define GMX_UTILITY_DEFAULTINITIALIZATIONALLOCATOR_H
  46
  47 #include <memory>
  48
  49 namespace gmx
  50 {
  51
  52 /*! \libinternal \brief Allocator adaptor that interposes construct() calls to
  53  * convert value initialization into default initialization.
  54  *
  55  * This can be used to avoid initialization e.g. on resize() in std::vector.
  56  */
  57 template <typename T, typename A = std::allocator<T> >
  58 class DefaultInitializationAllocator : public A
  59 {
  60     typedef std::allocator_traits<A> a_t;
  61     public:
  62         template <typename U> struct rebind {
  63             using other =
  64                     DefaultInitializationAllocator < U, typename a_t::template rebind_alloc < U>>;
  65         };
  66
  67         using A::A;
  68
  69         /*! \brief Constructs an object and default initializes */
  70         template <typename U>
  71         void construct(U* ptr)
  72         noexcept(std::is_nothrow_default_constructible<U>::value) {
  73             ::new(static_cast<void*>(ptr))U;
  74         }
  75
  76         /*! \brief Constructs an object and value initializes */
  77         template <typename U, typename ... Args>
  78         void construct(U* ptr, Args && ... args)
  79         {
  80             a_t::construct(static_cast<A &>(*this),
  81                            ptr, std::forward<Args>(args) ...);
  82         }
  83 };
  84
  85 }      // namespace gmx
  86
  87 #endif // GMX_UTILITY_DEFAULTINITIALIZATIONALLOCATOR_H