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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/util.hpp"
56 #define NBLIB_ALWAYS_INLINE __attribute((always_inline))
64 inline void gmxRVecZeroWorkaround([[maybe_unused]] T& value)
69 inline void gmxRVecZeroWorkaround<gmx::RVec>(gmx::RVec& value)
71 for (int i = 0; i < dimSize; ++i)
78 /*! \internal \brief object to store forces for multithreaded listed forces computation
84 using HashMap = std::unordered_map<int, T>;
87 ForceBuffer() : rangeStart(0), rangeEnd(0) { }
89 ForceBuffer(T* mbuf, int rs, int re) :
90 masterForceBuffer(mbuf),
96 void clear() { outliers.clear(); }
98 inline NBLIB_ALWAYS_INLINE T& operator[](int i)
100 if (i >= rangeStart && i < rangeEnd)
102 return masterForceBuffer[i];
106 if (outliers.count(i) == 0)
109 // if T = gmx::RVec, need to explicitly initialize it to zeros
110 detail::gmxRVecZeroWorkaround(zero);
117 typename HashMap::const_iterator begin() { return outliers.begin(); }
118 typename HashMap::const_iterator end() { return outliers.end(); }
120 [[nodiscard]] bool inRange(int index) const { return (index >= rangeStart && index < rangeEnd); }
123 T* masterForceBuffer;
133 static int computeChunkIndex(int index, int totalRange, int nSplits)
135 if (totalRange < nSplits)
137 // if there's more threads than particles
141 int splitLength = totalRange / nSplits;
142 return std::min(index / splitLength, nSplits - 1);
145 } // namespace detail
148 /*! \internal \brief splits an interaction tuple into nSplits interaction tuples
150 * \param interactions
151 * \param totalRange the number of particle sequence coordinates
152 * \param nSplits number to divide the total work by
156 std::vector<ListedInteractionData> splitListedWork(const ListedInteractionData& interactions,
160 std::vector<ListedInteractionData> workDivision(nSplits);
162 auto splitOneElement = [totalRange, nSplits, &workDivision](const auto& inputElement) {
163 // the index of inputElement in the ListedInteractionsTuple
164 constexpr int elementIndex =
165 FindIndex<std::decay_t<decltype(inputElement)>, ListedInteractionData>{};
167 // for now, copy all parameters to each split
168 // Todo: extract only the parameters needed for this split
169 for (auto& workDivisionSplit : workDivision)
171 std::get<elementIndex>(workDivisionSplit).parameters = inputElement.parameters;
174 // loop over all interactions in inputElement
175 for (const auto& interactionIndex : inputElement.indices)
177 // each interaction has multiple coordinate indices
178 // we must pick one of them to assign this interaction to one of the output index ranges
179 // Todo: count indices outside the current split range in order to minimize the buffer size
180 int representativeIndex =
181 *std::min_element(begin(interactionIndex), end(interactionIndex) - 1);
182 int splitIndex = detail::computeChunkIndex(representativeIndex, totalRange, nSplits);
184 std::get<elementIndex>(workDivision[splitIndex]).indices.push_back(interactionIndex);
188 // split each interaction type in the input interaction tuple
189 for_each_tuple(splitOneElement, interactions);
196 #undef NBLIB_ALWAYS_INLINE
198 #endif // NBLIB_LISTEDFORCSES_HELPERS_HPP