src/gromacs/math/arrayrefwithpadding.h

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
   3  *
   4  * Copyright (c) 2018,2019,2020, 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 /*! \file
  36  * \brief Declares gmx::ArrayRefWithPadding that refers to memory whose
  37  * size includes padding for SIMD operations.
  38  *
  39  * \author Mark Abraham <mark.j.abraham@gmail.com>
  40  *
  41  * \inpublicapi
  42  * \ingroup module_math
  43  */
  44 #ifndef GMX_MATH_ARRAYREFWITHPADDING_H
  45 #define GMX_MATH_ARRAYREFWITHPADDING_H
  46
  47 #include <cstddef>
  48
  49 #include "gromacs/utility/arrayref.h"
  50 #include "gromacs/utility/basedefinitions.h"
  51 #include "gromacs/utility/gmxassert.h"
  52
  53 namespace gmx
  54 {
  55
  56 /*! \brief Interface to a C array of T (or part of a std container of
  57  * T), that includes padding that is suitable for the kinds of SIMD
  58  * operations GROMACS uses.
  59  *
  60  * High level code e.g. in the force calculation routines need to hold
  61  * a non-owning view of memory and be able to create ArrayRef objects
  62  * that view padded or unpadded memory, suitable for the various
  63  * component routines. This class implements that non-owning view,
  64  * and the only available functionality refers to its size, and the
  65  * methods to create such ArrayRef objects.
  66  *
  67  * \copydoc ArrayRef
  68  * \inlibraryapi
  69  * \ingroup module_math
  70  */
  71 template<typename T>
  72 class ArrayRefWithPadding
  73 {
  74 public:
  75     //! Type of values stored in the reference.
  76     using value_type = T;
  77     //! Type for representing size of the reference.
  78     using size_type = index;
  79     //! Const pointer to an element.
  80     using const_pointer = const T*;
  81     //! Const iterator type to an element.
  82     using const_iterator = const T*;
  83     //! Pointer to an element.
  84     using pointer = T*;
  85     //! Iterator type to an element.
  86     using iterator = T*;
  87
  88     /*! \brief
  89      * Constructs an empty reference.
  90      */
  91     ArrayRefWithPadding() : begin_(nullptr), end_(nullptr), paddedEnd_(nullptr) {}
  92     /*! \brief
  93      * Constructs a reference to a particular range.
  94      *
  95      * \param[in] begin        Pointer to the beginning of a range.
  96      * \param[in] end          Pointer to the end of a range without padding.
  97      * \param[in] paddedEnd    Pointer to the end of a range including padding.
  98      *
  99      * Passed pointers must remain valid for the lifetime of this object.
 100      */
 101     ArrayRefWithPadding(pointer begin, pointer end, pointer paddedEnd) :
 102         begin_(begin),
 103         end_(end),
 104         paddedEnd_(paddedEnd)
 105     {
 106         GMX_ASSERT(end >= begin, "Invalid range");
 107         GMX_ASSERT(paddedEnd >= end, "Invalid range");
 108     }
 109     //! Copy constructor
 110     ArrayRefWithPadding(const ArrayRefWithPadding& o) :
 111         begin_(o.begin_),
 112         end_(o.end_),
 113         paddedEnd_(o.paddedEnd_)
 114     {
 115     }
 116     //! Move constructor
 117     ArrayRefWithPadding(ArrayRefWithPadding&& o) noexcept :
 118         begin_(std::move(o.begin_)),
 119         end_(std::move(o.end_)),
 120         paddedEnd_(std::move(o.paddedEnd_))
 121     {
 122     }
 123     /*! \brief Convenience overload constructor to make an ArrayRefWithPadding<const T> from a non-const one.
 124      *
 125      * \todo Use std::is_same_v when CUDA 11 is a requirement.
 126      */
 127     template<typename U, typename = std::enable_if_t<std::is_same<value_type, const typename std::remove_reference_t<U>::value_type>::value>>
 128     ArrayRefWithPadding(U&& o)
 129     {
 130         auto constArrayRefWithPadding = o.constArrayRefWithPadding();
 131         this->swap(constArrayRefWithPadding);
 132     }
 133     //! Copy assignment operator
 134     ArrayRefWithPadding& operator=(ArrayRefWithPadding const& o)
 135     {
 136         if (&o != this)
 137         {
 138             begin_     = o.begin_;
 139             end_       = o.end_;
 140             paddedEnd_ = o.paddedEnd_;
 141         }
 142         return *this;
 143     }
 144     //! Move assignment operator
 145     ArrayRefWithPadding& operator=(ArrayRefWithPadding&& o) noexcept
 146     {
 147         if (&o != this)
 148         {
 149             begin_     = std::move(o.begin_);
 150             end_       = std::move(o.end_);
 151             paddedEnd_ = std::move(o.paddedEnd_);
 152         }
 153         return *this;
 154     }
 155
 156     //! Return the size of the view, i.e with the padding.
 157     size_type size() const { return paddedEnd_ - begin_; }
 158     //! Whether the reference refers to no memory.
 159     bool empty() const { return begin_ == end_; }
 160
 161     //! Returns an ArrayRef of elements that does not include the padding region.
 162     ArrayRef<T> unpaddedArrayRef() { return { begin_, end_ }; }
 163     //! Returns an ArrayRef of const elements that does not include the padding region.
 164     ArrayRef<const T> unpaddedConstArrayRef() const { return { begin_, end_ }; }
 165     //! Returns an ArrayRef of elements that does include the padding region.
 166     ArrayRef<T> paddedArrayRef() { return { begin_, paddedEnd_ }; }
 167     //! Returns an ArrayRef of const elements that does include the padding region.
 168     ArrayRef<const T> paddedConstArrayRef() const { return { begin_, paddedEnd_ }; }
 169     //! Returns an identical ArrayRefWithPadding that refers to const elements.
 170     ArrayRefWithPadding<const T> constArrayRefWithPadding() const
 171     {
 172         return { begin_, end_, paddedEnd_ };
 173     }
 174     /*! \brief
 175      * Swaps referenced memory with the other object.
 176      *
 177      * The actual memory areas are not modified, only the references are
 178      * swapped.
 179      */
 180     void swap(ArrayRefWithPadding<T>& other)
 181     {
 182         std::swap(begin_, other.begin_);
 183         std::swap(end_, other.end_);
 184         std::swap(paddedEnd_, other.paddedEnd_);
 185     }
 186
 187 private:
 188     pointer begin_;
 189     pointer end_;
 190     pointer paddedEnd_;
 191 };
 192
 193 } // namespace gmx
 194
 195 #endif