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37 * \brief API for neighborhood searching for analysis.
39 * The main part of the API is the class gmx::AnalysisNeighborhood.
40 * See \ref page_analysisnbsearch for an overview.
42 * The classes within this file can be used independently of the other parts
43 * of the selection module.
45 * \author Teemu Murtola <teemu.murtola@gmail.com>
47 * \ingroup module_selection
49 #ifndef GMX_SELECTION_NBSEARCH_H
50 #define GMX_SELECTION_NBSEARCH_H
55 #include "gromacs/math/vec.h"
56 #include "gromacs/math/vectypes.h"
57 #include "gromacs/utility/arrayref.h"
58 #include "gromacs/utility/classhelpers.h"
59 #include "gromacs/utility/gmxassert.h"
60 #include "gromacs/utility/real.h"
70 class AnalysisNeighborhoodSearchImpl;
71 class AnalysisNeighborhoodPairSearchImpl;
72 }; // namespace internal
74 class AnalysisNeighborhoodSearch;
75 class AnalysisNeighborhoodPairSearch;
78 * Input positions for neighborhood searching.
80 * This class supports uniformly specifying sets of positions for various
81 * methods in the analysis neighborhood searching classes
82 * (AnalysisNeighborhood and AnalysisNeighborhoodSearch).
84 * Note that copies are not made: only a reference to the positions passed to
85 * the constructors are kept. The caller is responsible to ensure that those
86 * positions remain in scope as long as the neighborhood search object requires
89 * Also note that in addition to constructors here, Selection and
90 * SelectionPosition provide conversions operators to this type. It is done
91 * this way to not introduce a cyclic dependency between the selection code and
92 * the neighborhood search code, which in turn allows splitting this search
93 * code into a separate lower-level module if desired at some point.
95 * Methods in this class do not throw.
98 * \ingroup module_selection
100 class AnalysisNeighborhoodPositions
104 * Initializes positions from a single position vector.
106 * For positions initialized this way, AnalysisNeighborhoodPair always
107 * returns zero in the corresponding index.
109 * This constructor is not explicit to allow directly passing an rvec
110 * to methods that accept positions.
112 AnalysisNeighborhoodPositions(const rvec& x) :
116 exclusionIds_(nullptr),
121 * Initializes positions from an array of position vectors.
123 AnalysisNeighborhoodPositions(const rvec x[], int count) :
127 exclusionIds_(nullptr),
132 * Initializes positions from a vector of position vectors.
134 AnalysisNeighborhoodPositions(const std::vector<RVec>& x) :
137 x_(as_rvec_array(x.data())),
138 exclusionIds_(nullptr),
144 * Sets indices to use for mapping exclusions to these positions.
146 * The exclusion IDs can always be set, but they are ignored unless
147 * actual exclusions have been set with
148 * AnalysisNeighborhood::setTopologyExclusions().
150 AnalysisNeighborhoodPositions& exclusionIds(ArrayRef<const int> ids)
152 GMX_ASSERT(ssize(ids) == count_, "Exclusion id array should match the number of positions");
153 exclusionIds_ = ids.data();
157 * Sets indices that select a subset of all positions from the array.
159 * If called, selected positions from the array of positions passed to
160 * the constructor is used instead of the whole array.
161 * All returned indices from AnalysisNeighborhoodPair objects are
162 * indices to the \p indices array passed here.
164 AnalysisNeighborhoodPositions& indexed(ArrayRef<const int> indices)
166 count_ = ssize(indices);
167 indices_ = indices.data();
172 * Selects a single position to use from an array.
174 * If called, a single position from the array of positions passed to
175 * the constructor is used instead of the whole array.
176 * In contrast to the AnalysisNeighborhoodPositions(const rvec &)
177 * constructor, AnalysisNeighborhoodPair objects return \p index
180 * If used together with indexed(), \p index references the index array
181 * passed to indexed() instead of the position array.
183 AnalysisNeighborhoodPositions& selectSingleFromArray(int index)
185 GMX_ASSERT(index >= 0 && index < count_, "Invalid position index");
194 const int* exclusionIds_;
197 //! To access the positions for initialization.
198 friend class internal::AnalysisNeighborhoodSearchImpl;
199 //! To access the positions for initialization.
200 friend class internal::AnalysisNeighborhoodPairSearchImpl;
204 * Neighborhood searching for analysis tools.
206 * See \ref page_analysisnbsearch for an overview.
208 * To use the search, create an object of this type, call setCutoff() to
209 * initialize it, and then repeatedly call initSearch() to start a search with
210 * different sets of reference positions. For each set of reference positions,
211 * use methods in the returned AnalysisNeighborhoodSearch to find the reference
212 * positions that are within the given cutoff from a provided position.
214 * initSearch() is thread-safe and can be called from multiple threads. Each
215 * call returns a different instance of the search object that can be used
216 * independently of the others. The returned AnalysisNeighborhoodSearch
217 * objects are also thread-safe, and can be used concurrently from multiple
218 * threads. It is also possible to create multiple concurrent searches within
222 * Generalize the exclusion machinery to make it easier to use for other cases
223 * than atom-atom exclusions from the topology.
226 * \ingroup module_selection
228 class AnalysisNeighborhood
231 //! Searching algorithm to use.
234 //! Select algorithm based on heuristic efficiency considerations.
235 eSearchMode_Automatic,
236 //! Use a simple loop over all pairs.
238 //! Use grid-based searching whenever possible.
242 //! Creates an uninitialized neighborhood search.
243 AnalysisNeighborhood();
244 ~AnalysisNeighborhood();
247 * Sets cutoff distance for the neighborhood searching.
249 * \param[in] cutoff Cutoff distance for the search
250 * (<=0 stands for no cutoff).
252 * Currently, can only be called before the first call to initSearch().
253 * If this method is not called, no cutoff is used in the searches.
257 void setCutoff(real cutoff);
259 * Sets the search to only happen in the XY plane.
261 * Z component of the coordinates is not used in the searching,
262 * and returned distances are computed in the XY plane.
263 * Only boxes with the third box vector parallel to the Z axis are
264 * currently implemented.
268 void setXYMode(bool bXY);
270 * Sets atom exclusions from a topology.
272 * The \p excls structure specifies the exclusions from test positions
273 * to reference positions, i.e., a block starting at `excls->index[i]`
274 * specifies the exclusions for test position `i`, and the indices in
275 * `excls->a` are indices of the reference positions. If `excls->nr`
276 * is smaller than a test position id, then such test positions do not
277 * have any exclusions.
278 * It is assumed that the indices within a block of indices in
279 * `excls->a` is ascending.
283 * \see AnalysisNeighborhoodPositions::exclusionIds()
285 void setTopologyExclusions(const t_blocka* excls);
287 * Sets the algorithm to use for searching.
289 * \param[in] mode Search mode to use.
291 * Note that if \p mode is \ref eSearchMode_Grid, it is still only a
292 * suggestion: grid-based searching may not be possible with the
293 * provided input, in which case a simple search is still used.
294 * This is mainly useful for testing purposes to force a mode.
298 void setMode(SearchMode mode);
299 //! Returns the currently active search mode.
300 SearchMode mode() const;
303 * Initializes neighborhood search for a set of positions.
305 * \param[in] pbc PBC information for the frame.
306 * \param[in] positions Set of reference positions to use.
307 * \returns Search object that can be used to find positions from
308 * \p x within the given cutoff.
309 * \throws std::bad_alloc if out of memory.
311 * Currently, the input positions cannot use
312 * AnalysisNeighborhoodPositions::selectSingleFromArray().
314 AnalysisNeighborhoodSearch initSearch(const t_pbc* pbc, const AnalysisNeighborhoodPositions& positions);
319 PrivateImplPointer<Impl> impl_;
323 * Value type to represent a pair of positions found in neighborhood searching.
325 * Methods in this class do not throw.
328 * \ingroup module_selection
330 class AnalysisNeighborhoodPair
333 //! Initializes an invalid pair.
334 AnalysisNeighborhoodPair() : refIndex_(-1), testIndex_(0), distance2_(0.0), dx_() {}
335 //! Initializes a pair object with the given data.
336 AnalysisNeighborhoodPair(int refIndex, int testIndex, real distance2, const rvec dx) :
338 testIndex_(testIndex),
339 distance2_(distance2),
346 * Whether this pair is valid.
348 * If isValid() returns false, other methods should not be called.
350 bool isValid() const { return refIndex_ >= 0; }
353 * Returns the index of the reference position in the pair.
355 * This index is always the index into the position array provided to
356 * AnalysisNeighborhood::initSearch().
360 GMX_ASSERT(isValid(), "Accessing invalid object");
364 * Returns the index of the test position in the pair.
366 * The contents of this index depends on the context (method call) that
368 * If there was no array in the call, this index is zero.
370 int testIndex() const
372 GMX_ASSERT(isValid(), "Accessing invalid object");
376 * Returns the squared distance between the pair of positions.
378 real distance2() const
380 GMX_ASSERT(isValid(), "Accessing invalid object");
384 * Returns the shortest vector between the pair of positions.
386 * The vector is from the test position to the reference position.
388 const rvec& dx() const
390 GMX_ASSERT(isValid(), "Accessing invalid object");
402 * Initialized neighborhood search with a fixed set of reference positions.
404 * An instance of this class is obtained through
405 * AnalysisNeighborhood::initSearch(), and can be used to do multiple searches
406 * against the provided set of reference positions.
407 * It is possible to create concurrent pair searches (including from different
408 * threads), as well as call other methods in this class while a pair search is
411 * This class works like a pointer: copies of it point to the same search.
412 * In general, avoid creating copies, and only use the copy/assignment support
413 * for moving the variable around. With C++11, this class would best be
416 * Methods in this class do not throw unless otherwise indicated.
419 * Make it such that reset() is not necessary to call in code that repeatedly
420 * assigns the result of AnalysisNeighborhood::initSearch() to the same
421 * variable (see sm_distance.cpp).
424 * Consider removing minimumDistance(), as nearestPoint() already returns the
428 * \ingroup module_selection
430 class AnalysisNeighborhoodSearch
434 * Internal short-hand type for a pointer to the implementation class.
436 * shared_ptr is used here to automatically keep a reference count to
437 * track whether an implementation class is still used outside the
438 * AnalysisNeighborhood object. Ownership currently always stays with
439 * AnalysisNeighborhood; it always keeps one instance of the pointer.
441 typedef std::shared_ptr<internal::AnalysisNeighborhoodSearchImpl> ImplPointer;
444 * Initializes an invalid search.
446 * Such an object cannot be used for searching. It needs to be
447 * assigned a value from AnalysisNeighborhood::initSearch() before it
448 * can be used. Provided to allow declaring a variable to hold the
449 * search before calling AnalysisNeighborhood::initSearch().
451 AnalysisNeighborhoodSearch();
453 * Internally initialize the search.
455 * Used to implement AnalysisNeighborhood::initSearch().
456 * Cannot be called from user code.
458 explicit AnalysisNeighborhoodSearch(const ImplPointer& impl);
461 * Clears this search.
463 * Equivalent to \c "*this = AnalysisNeighborhoodSearch();".
464 * Currently, this is necessary to avoid unnecessary memory allocation
465 * if the previous search variable is still in scope when you want to
466 * call AnalysisNeighborhood::initSearch() again.
471 * Returns the searching algorithm that this search is using.
473 * The return value is never AnalysisNeighborhood::eSearchMode_Automatic.
475 AnalysisNeighborhood::SearchMode mode() const;
478 * Checks whether a point is within a neighborhood.
480 * \param[in] positions Set of test positions to use.
481 * \returns true if any of the test positions is within the cutoff of
482 * any reference position.
484 bool isWithin(const AnalysisNeighborhoodPositions& positions) const;
486 * Calculates the minimum distance from the reference points.
488 * \param[in] positions Set of test positions to use.
489 * \returns The distance to the nearest reference position, or the
490 * cutoff value if there are no reference positions within the
493 real minimumDistance(const AnalysisNeighborhoodPositions& positions) const;
495 * Finds the closest reference point.
497 * \param[in] positions Set of test positions to use.
498 * \returns The reference index identifies the reference position
499 * that is closest to the test positions.
500 * The test index identifies the test position that is closest to
501 * the provided test position. The returned pair is invalid if
502 * no reference position is within the cutoff.
504 AnalysisNeighborhoodPair nearestPoint(const AnalysisNeighborhoodPositions& positions) const;
507 * Starts a search to find all reference position pairs within a cutoff.
509 * \returns Initialized search object to loop through all reference
510 * position pairs within the configured cutoff.
511 * \throws std::bad_alloc if out of memory.
513 * This works as if the reference positions were passed to
514 * startPairSearch(), except that it only returns each pair once,
515 * instead of returning both i-j and j-i pairs, as startPairSearch()
516 * does. i-i pairs are not returned. Note that the order of ref/test
517 * indices in the returned pairs is not predictable. That is, one of
518 * i-j or j-i is always returned, but there is no control which one.
520 AnalysisNeighborhoodPairSearch startSelfPairSearch() const;
523 * Starts a search to find reference positions within a cutoff.
525 * \param[in] positions Set of test positions to use.
526 * \returns Initialized search object to loop through all reference
527 * positions within the configured cutoff.
528 * \throws std::bad_alloc if out of memory.
530 * If you want to pass the same positions here as you used for the
531 * reference positions, consider using startSelfPairSearch().
532 * It can be up to 50% faster.
534 AnalysisNeighborhoodPairSearch startPairSearch(const AnalysisNeighborhoodPositions& positions) const;
537 typedef internal::AnalysisNeighborhoodSearchImpl Impl;
543 * Initialized neighborhood pair search with a fixed set of positions.
545 * This class is used to loop through pairs of neighbors within the cutoff
546 * provided to AnalysisNeighborhood. The following code demonstrates its use:
548 gmx::AnalysisNeighborhood nb;
549 nb.setCutoff(cutoff);
550 gmx::AnalysisNeighborhoodPositions refPos(xref, nref);
551 gmx::AnalysisNeighborhoodSearch search = nb.initSearch(pbc, refPos);
552 gmx::AnalysisNeighborhoodPairSearch pairSearch = search.startPairSearch(selection);
553 gmx::AnalysisNeighborhoodPair pair;
554 while (pairSearch.findNextPair(&pair))
556 // <do something for each found pair the information in pair>
560 * It is not possible to use a single search object from multiple threads
563 * This class works like a pointer: copies of it point to the same search.
564 * In general, avoid creating copies, and only use the copy/assignment support
565 * for moving the variable around. With C++11, this class would best be
568 * Methods in this class do not throw.
571 * \ingroup module_selection
573 class AnalysisNeighborhoodPairSearch
577 * Internal short-hand type for a pointer to the implementation class.
579 * See AnalysisNeighborhoodSearch::ImplPointer for rationale of using
580 * shared_ptr and ownership semantics.
582 typedef std::shared_ptr<internal::AnalysisNeighborhoodPairSearchImpl> ImplPointer;
585 * Internally initialize the search.
587 * Used to implement AnalysisNeighborhoodSearch::startPairSearch().
588 * Cannot be called from user code.
590 explicit AnalysisNeighborhoodPairSearch(const ImplPointer& impl);
593 * Finds the next pair within the cutoff.
595 * \param[out] pair Information about the found pair.
596 * \returns false if there were no more pairs.
598 * If the method returns false, \p pair will be invalid.
600 * \see AnalysisNeighborhoodPair
601 * \see AnalysisNeighborhoodSearch::startPairSearch()
603 bool findNextPair(AnalysisNeighborhoodPair* pair);
605 * Skip remaining pairs for a test position in the search.
607 * When called after findNextPair(), makes subsequent calls to
608 * findNextPair() skip any pairs that have the same test position as
609 * that previously returned.
610 * This is useful if the caller wants to search whether any reference
611 * position within the cutoff satisfies some condition. This method
612 * can be used to skip remaining pairs after the first such position
613 * has been found if the remaining pairs would not have an effect on
616 void skipRemainingPairsForTestPosition();