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37 * \brief Implements GPU Force Reduction using SYCL
39 * \author Alan Gray <alang@nvidia.com>
40 * \author Andrey Alekseenko <al42and@gmail.com>
42 * \ingroup module_mdlib
47 #include "gpuforcereduction_impl_internal.h"
51 #include "gromacs/gpu_utils/gmxsycl.h"
52 #include "gromacs/gpu_utils/devicebuffer.h"
53 #include "gromacs/gpu_utils/gpu_utils.h"
54 #include "gromacs/gpu_utils/gpueventsynchronizer.h"
55 #include "gromacs/utility/template_mp.h"
57 //! \brief Class name for reduction kernel
58 template<bool addRvecForce, bool accumulateForce>
64 using cl::sycl::access::mode;
66 //! \brief Function returning the force reduction kernel lambda.
67 template<bool addRvecForce, bool accumulateForce>
68 static auto reduceKernel(cl::sycl::handler& cgh,
69 DeviceAccessor<Float3, mode::read> a_nbnxmForce,
70 OptionalAccessor<Float3, mode::read, addRvecForce> a_rvecForceToAdd,
71 DeviceAccessor<Float3, accumulateForce ? mode::read_write : mode::write> a_forceTotal,
72 DeviceAccessor<int, cl::sycl::access::mode::read> a_cell,
75 a_nbnxmForce.bind(cgh);
76 if constexpr (addRvecForce)
78 a_rvecForceToAdd.bind(cgh);
80 a_forceTotal.bind(cgh);
83 return [=](cl::sycl::id<1> itemIdx) {
84 // Set to nbnxnm force, then perhaps accumulate further to it
85 Float3 temp = a_nbnxmForce[a_cell[itemIdx]];
87 if constexpr (accumulateForce)
89 temp += a_forceTotal[itemIdx + atomStart];
92 if constexpr (addRvecForce)
94 temp += a_rvecForceToAdd[itemIdx + atomStart];
97 a_forceTotal[itemIdx + atomStart] = temp;
101 //! \brief Force reduction SYCL kernel launch code.
102 template<bool addRvecForce, bool accumulateForce>
103 static void launchReductionKernel_(const int numAtoms,
105 const DeviceBuffer<Float3>& b_nbnxmForce,
106 const DeviceBuffer<Float3>& b_rvecForceToAdd,
107 DeviceBuffer<Float3>& b_forceTotal,
108 const DeviceBuffer<int>& b_cell,
109 const DeviceStream& deviceStream)
111 const cl::sycl::range<1> rangeNumAtoms(numAtoms);
112 cl::sycl::queue queue = deviceStream.stream();
114 // We only need parts of b_rvecForceToAdd and b_forceTotal, so sub-buffers would be appropriate.
115 // But hipSYCL does not support them yet, nor plans to. See Issue #4019.
117 queue.submit([&](cl::sycl::handler& cgh) {
118 auto kernel = reduceKernel<addRvecForce, accumulateForce>(
119 cgh, b_nbnxmForce, b_rvecForceToAdd, b_forceTotal, b_cell, atomStart);
120 cgh.parallel_for<ReduceKernel<addRvecForce, accumulateForce>>(rangeNumAtoms, kernel);
124 /*! \brief Select templated Force reduction kernel and launch it. */
125 void launchForceReductionKernel(int numAtoms,
129 DeviceBuffer<Float3> d_nbnxmForceToAdd,
130 DeviceBuffer<Float3> d_rvecForceToAdd,
131 DeviceBuffer<Float3> d_baseForce,
132 DeviceBuffer<int> d_cell,
133 const DeviceStream& deviceStream)
135 dispatchTemplatedFunction(
136 [&](auto addRvecForce_, auto accumulateForce_) {
137 return launchReductionKernel_<addRvecForce_, accumulateForce_>(
138 numAtoms, atomStart, d_nbnxmForceToAdd, d_rvecForceToAdd, d_baseForce, d_cell, deviceStream);