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36 * \brief Declare interface for GPU execution for NBNXN module
38 * \author Szilard Pall <pall.szilard@gmail.com>
39 * \author Mark Abraham <mark.j.abraham@gmail.com>
40 * \ingroup module_mdlib
43 #ifndef GMX_MDLIB_NBNXN_GPU_H
44 #define GMX_MDLIB_NBNXN_GPU_H
46 #include "gromacs/gpu_utils/gpu_macros.h"
47 #include "gromacs/math/vectypes.h"
48 #include "gromacs/mdlib/nbnxn_gpu_types.h"
49 #include "gromacs/utility/basedefinitions.h"
50 #include "gromacs/utility/real.h"
52 struct nbnxn_atomdata_t;
53 enum class GpuTaskCompletion;
56 * Launch asynchronously the xq buffer host to device copy.
58 * The nonlocal copy is skipped if there is no dependent work to do,
59 * neither non-local nonbonded interactions nor bonded GPU work.
61 * \param [in] nb GPU nonbonded data.
62 * \param [in] nbdata Host-side atom data structure.
63 * \param [in] iloc Interaction locality flag.
64 * \param [in] haveOtherWork True if there are other tasks that require the nbnxn coordinate input.
67 void nbnxn_gpu_copy_xq_to_gpu(gmx_nbnxn_gpu_t gmx_unused *nb,
68 const struct nbnxn_atomdata_t gmx_unused *nbdata,
70 bool gmx_unused haveOtherWork) GPU_FUNC_TERM
73 * Launch asynchronously the nonbonded force calculations.
75 * Also launches the initial pruning of a fresh list after search.
77 * The local and non-local interaction calculations are launched in two
78 * separate streams. If there is no work (i.e. empty pair list), the
79 * force kernel launch is omitted.
83 void nbnxn_gpu_launch_kernel(gmx_nbnxn_gpu_t gmx_unused *nb,
85 int gmx_unused iloc) GPU_FUNC_TERM
88 * Launch asynchronously the nonbonded prune-only kernel.
90 * The local and non-local list pruning are launched in their separate streams.
92 * Notes for future scheduling tuning:
93 * Currently we schedule the dynamic pruning between two MD steps *after* both local and
94 * nonlocal force D2H transfers completed. We could launch already after the cpyback
95 * is launched, but we want to avoid prune kernels (especially in the non-local
96 * high prio-stream) competing with nonbonded work.
98 * However, this is not ideal as this schedule does not expose the available
99 * concurrency. The dynamic pruning kernel:
100 * - should be allowed to overlap with any task other than force compute, including
101 * transfers (F D2H and the next step's x H2D as well as force clearing).
102 * - we'd prefer to avoid competition with non-bonded force kernels belonging
103 * to the same rank and ideally other ranks too.
105 * In the most general case, the former would require scheduling pruning in a separate
106 * stream and adding additional event sync points to ensure that force kernels read
107 * consistent pair list data. This would lead to some overhead (due to extra
108 * cudaStreamWaitEvent calls, 3-5 us/call) which we might be able to live with.
109 * The gains from additional overlap might not be significant as long as
110 * update+constraints anyway takes longer than pruning, but there will still
111 * be use-cases where more overlap may help (e.g. multiple ranks per GPU,
112 * no/hbonds only constraints).
113 * The above second point is harder to address given that multiple ranks will often
114 * share a GPU. Ranks that complete their nonbondeds sooner can schedule pruning earlier
115 * and without a third priority level it is difficult to avoid some interference of
116 * prune kernels with force tasks (in particular preemption of low-prio local force task).
118 * \param [inout] nb GPU nonbonded data.
119 * \param [in] iloc Interaction locality flag.
120 * \param [in] numParts Number of parts the pair list is split into in the rolling kernel.
123 void nbnxn_gpu_launch_kernel_pruneonly(gmx_nbnxn_gpu_t gmx_unused *nb,
125 int gmx_unused numParts) GPU_FUNC_TERM
128 * Launch asynchronously the download of nonbonded forces from the GPU
129 * (and energies/shift forces if required).
130 * When haveOtherWork=true, the copy-back is done even when there was
131 * no non-bonded work.
134 void nbnxn_gpu_launch_cpyback(gmx_nbnxn_gpu_t gmx_unused *nb,
135 struct nbnxn_atomdata_t gmx_unused *nbatom,
136 int gmx_unused flags,
138 bool gmx_unused haveOtherWork) GPU_FUNC_TERM
140 /*! \brief Attempts to complete nonbonded GPU task.
142 * This function attempts to complete the nonbonded task (both GPU and CPU auxiliary work).
143 * Success, i.e. that the tasks completed and results are ready to be consumed, is signaled
144 * by the return value (always true if blocking wait mode requested).
146 * The \p completionKind parameter controls whether the behavior is non-blocking
147 * (achieved by passing GpuTaskCompletion::Check) or blocking wait until the results
148 * are ready (when GpuTaskCompletion::Wait is passed).
149 * As the "Check" mode the function will return immediately if the GPU stream
150 * still contain tasks that have not completed, it allows more flexible overlapping
151 * of work on the CPU with GPU execution.
153 * Note that it is only safe to use the results, and to continue to the next MD
154 * step when this function has returned true which indicates successful completion of
155 * - All nonbonded GPU tasks: both compute and device transfer(s)
156 * - auxiliary tasks: updating the internal module state (timing accumulation, list pruning states) and
157 * - internal staging reduction of (\p fshift, \p e_el, \p e_lj).
159 * TODO: improve the handling of outputs e.g. by ensuring that this function explcitly returns the
160 * force buffer (instead of that being passed only to nbnxn_gpu_launch_cpyback()) and by returning
161 * the energy and Fshift contributions for some external/centralized reduction.
163 * \param[in] nb The nonbonded data GPU structure
164 * \param[in] flags Force flags
165 * \param[in] aloc Atom locality identifier
166 * \param[in] haveOtherWork Tells whether there is other work than non-bonded work in the nbnxn stream(s)
167 * \param[out] e_lj Pointer to the LJ energy output to accumulate into
168 * \param[out] e_el Pointer to the electrostatics energy output to accumulate into
169 * \param[out] fshift Pointer to the shift force buffer to accumulate into
170 * \param[in] completionKind Indicates whether nnbonded task completion should only be checked rather than waited for
171 * \returns True if the nonbonded tasks associated with \p aloc locality have completed
174 bool nbnxn_gpu_try_finish_task(gmx_nbnxn_gpu_t gmx_unused *nb,
175 int gmx_unused flags,
177 bool gmx_unused haveOtherWork,
178 real gmx_unused *e_lj,
179 real gmx_unused *e_el,
180 rvec gmx_unused *fshift,
181 GpuTaskCompletion gmx_unused completionKind) GPU_FUNC_TERM_WITH_RETURN(false)
183 /*! \brief Completes the nonbonded GPU task blocking until GPU tasks and data
184 * transfers to finish.
186 * Also does timing accounting and reduction of the internal staging buffers.
187 * As this is called at the end of the step, it also resets the pair list and
190 * \param[in] nb The nonbonded data GPU structure
191 * \param[in] flags Force flags
192 * \param[in] aloc Atom locality identifier
193 * \param[in] haveOtherWork Tells whether there is other work than non-bonded work in the nbnxn stream(s)
194 * \param[out] e_lj Pointer to the LJ energy output to accumulate into
195 * \param[out] e_el Pointer to the electrostatics energy output to accumulate into
196 * \param[out] fshift Pointer to the shift force buffer to accumulate into
199 void nbnxn_gpu_wait_finish_task(gmx_nbnxn_gpu_t gmx_unused *nb,
200 int gmx_unused flags,
202 bool gmx_unused haveOtherWork,
203 real gmx_unused *e_lj,
204 real gmx_unused *e_el,
205 rvec gmx_unused *fshift) GPU_FUNC_TERM
207 /*! \brief Selects the Ewald kernel type, analytical or tabulated, single or twin cut-off. */
209 int nbnxn_gpu_pick_ewald_kernel_type(bool gmx_unused bTwinCut) GPU_FUNC_TERM_WITH_RETURN(-1)