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37 * Helper data structures and utility functions for the nblib force calculator.
38 * Intended for internal use.
40 * \author Victor Holanda <victor.holanda@cscs.ch>
41 * \author Joe Jordan <ejjordan@kth.se>
42 * \author Prashanth Kanduri <kanduri@cscs.ch>
43 * \author Sebastian Keller <keller@cscs.ch>
44 * \author Artem Zhmurov <zhmurov@gmail.com>
47 #ifndef NBLIB_LISTEDFORCSES_HELPERS_HPP
48 #define NBLIB_LISTEDFORCSES_HELPERS_HPP
50 #include <unordered_map>
52 #include "nblib/pbc.hpp"
53 #include "definitions.h"
54 #include "nblib/util/internal.h"
62 inline void gmxRVecZeroWorkaround([[maybe_unused]] T& value)
67 inline void gmxRVecZeroWorkaround<gmx::RVec>(gmx::RVec& value)
69 for (int i = 0; i < dimSize; ++i)
76 /*! \internal \brief object to store forces for multithreaded listed forces computation
82 using HashMap = std::unordered_map<int, T>;
85 ForceBuffer() : rangeStart(0), rangeEnd(0) { }
87 ForceBuffer(T* mbuf, int rs, int re) :
88 masterForceBuffer(mbuf),
94 void clear() { outliers.clear(); }
96 inline NBLIB_ALWAYS_INLINE T& operator[](int i)
98 if (i >= rangeStart && i < rangeEnd)
100 return masterForceBuffer[i];
104 if (outliers.count(i) == 0)
107 // if T = gmx::RVec, need to explicitly initialize it to zeros
108 detail::gmxRVecZeroWorkaround(zero);
115 typename HashMap::const_iterator begin() { return outliers.begin(); }
116 typename HashMap::const_iterator end() { return outliers.end(); }
118 [[nodiscard]] bool inRange(int index) const { return (index >= rangeStart && index < rangeEnd); }
121 T* masterForceBuffer;
131 static int computeChunkIndex(int index, int totalRange, int nSplits)
133 if (totalRange < nSplits)
135 // if there's more threads than particles
139 int splitLength = totalRange / nSplits;
140 return std::min(index / splitLength, nSplits - 1);
143 } // namespace detail
146 /*! \internal \brief splits an interaction tuple into nSplits interaction tuples
148 * \param interactions
149 * \param totalRange the number of particle sequence coordinates
150 * \param nSplits number to divide the total work by
154 std::vector<ListedInteractionData> splitListedWork(const ListedInteractionData& interactions,
158 std::vector<ListedInteractionData> workDivision(nSplits);
160 auto splitOneElement = [totalRange, nSplits, &workDivision](const auto& inputElement) {
161 // the index of inputElement in the ListedInteractionsTuple
162 constexpr int elementIndex =
163 FindIndex<std::decay_t<decltype(inputElement)>, ListedInteractionData>{};
165 // for now, copy all parameters to each split
166 // Todo: extract only the parameters needed for this split
167 for (auto& workDivisionSplit : workDivision)
169 std::get<elementIndex>(workDivisionSplit).parameters = inputElement.parameters;
172 // loop over all interactions in inputElement
173 for (const auto& interactionIndex : inputElement.indices)
175 // each interaction has multiple coordinate indices
176 // we must pick one of them to assign this interaction to one of the output index ranges
177 // Todo: count indices outside the current split range in order to minimize the buffer size
178 int representativeIndex =
179 *std::min_element(begin(interactionIndex), end(interactionIndex) - 1);
180 int splitIndex = detail::computeChunkIndex(representativeIndex, totalRange, nSplits);
182 std::get<elementIndex>(workDivision[splitIndex]).indices.push_back(interactionIndex);
186 // split each interaction type in the input interaction tuple
187 for_each_tuple(splitOneElement, interactions);
194 #endif // NBLIB_LISTEDFORCSES_HELPERS_HPP