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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 "gromacs/utility/arrayref.h"
54 #include "nblib/pbc.hpp"
55 #include "definitions.h"
56 #include "nblib/util/util.hpp"
58 #define NBLIB_ALWAYS_INLINE __attribute((always_inline))
66 inline void gmxRVecZeroWorkaround([[maybe_unused]] T& value)
71 inline void gmxRVecZeroWorkaround<gmx::RVec>(gmx::RVec& value)
73 for (int i = 0; i < dimSize; ++i)
80 /*! \internal \brief proxy object to access forces in an underlying buffer
82 * Depending on the index, either the underlying master buffer, or local
83 * storage for outliers is accessed. This object does not own the master buffer.
87 class ForceBufferProxy
89 using HashMap = std::unordered_map<int, T>;
92 ForceBufferProxy() : rangeStart_(0), rangeEnd_(0) { }
94 ForceBufferProxy(int rangeStart, int rangeEnd) : rangeStart_(rangeStart), rangeEnd_(rangeEnd)
98 void clearOutliers() { outliers.clear(); }
100 inline NBLIB_ALWAYS_INLINE T& operator[](int i)
102 if (i >= rangeStart_ && i < rangeEnd_)
104 return masterForceBuffer[i];
108 if (outliers.count(i) == 0)
111 // if T = gmx::RVec, need to explicitly initialize it to zeros
112 detail::gmxRVecZeroWorkaround(zero);
119 typename HashMap::const_iterator begin() { return outliers.begin(); }
120 typename HashMap::const_iterator end() { return outliers.end(); }
122 [[nodiscard]] bool inRange(int index) const { return (index >= rangeStart_ && index < rangeEnd_); }
124 void setMasterBuffer(gmx::ArrayRef<T> buffer) { masterForceBuffer = buffer; }
127 gmx::ArrayRef<T> masterForceBuffer;
137 static int computeChunkIndex(int index, int totalRange, int nSplits)
139 if (totalRange < nSplits)
141 // if there's more threads than particles
145 int splitLength = totalRange / nSplits;
146 return std::min(index / splitLength, nSplits - 1);
149 } // namespace detail
152 /*! \internal \brief splits an interaction tuple into nSplits interaction tuples
154 * \param interactions
155 * \param totalRange the number of particle sequence coordinates
156 * \param nSplits number to divide the total work by
160 std::vector<ListedInteractionData> splitListedWork(const ListedInteractionData& interactions,
164 std::vector<ListedInteractionData> workDivision(nSplits);
166 auto splitOneElement = [totalRange, nSplits, &workDivision](const auto& inputElement) {
167 // the index of inputElement in the ListedInteractionsTuple
168 constexpr int elementIndex =
169 FindIndex<std::decay_t<decltype(inputElement)>, ListedInteractionData>{};
171 // for now, copy all parameters to each split
172 // Todo: extract only the parameters needed for this split
173 for (auto& workDivisionSplit : workDivision)
175 std::get<elementIndex>(workDivisionSplit).parameters = inputElement.parameters;
178 // loop over all interactions in inputElement
179 for (const auto& interactionIndex : inputElement.indices)
181 // each interaction has multiple coordinate indices
182 // we must pick one of them to assign this interaction to one of the output index ranges
183 // Todo: count indices outside the current split range in order to minimize the buffer size
184 int representativeIndex =
185 *std::min_element(begin(interactionIndex), end(interactionIndex) - 1);
186 int splitIndex = detail::computeChunkIndex(representativeIndex, totalRange, nSplits);
188 std::get<elementIndex>(workDivision[splitIndex]).indices.push_back(interactionIndex);
192 // split each interaction type in the input interaction tuple
193 for_each_tuple(splitOneElement, interactions);
200 #undef NBLIB_ALWAYS_INLINE
202 #endif // NBLIB_LISTEDFORCSES_HELPERS_HPP