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37 * \brief Implements GPU Force Reduction using CUDA
39 * \author Alan Gray <alang@nvidia.com>
41 * \ingroup module_mdlib
46 #include "gpuforcereduction_impl.cuh"
50 #include "gromacs/gpu_utils/cudautils.cuh"
51 #include "gromacs/gpu_utils/device_context.h"
52 #include "gromacs/gpu_utils/devicebuffer.h"
53 #include "gromacs/gpu_utils/gpu_utils.h"
54 #include "gromacs/gpu_utils/gpueventsynchronizer.cuh"
55 #include "gromacs/gpu_utils/typecasts.cuh"
56 #include "gromacs/gpu_utils/vectype_ops.cuh"
57 #include "gromacs/utility/gmxassert.h"
59 #include "gpuforcereduction.h"
64 constexpr static int c_threadsPerBlock = 128;
66 typedef struct rvecDeviceForceData rvecDeviceForceData_t;
69 template<bool addRvecForce, bool accumulateForce>
70 static __global__ void reduceKernel(const float3* __restrict__ gm_nbnxmForce,
71 const float3* __restrict__ rvecForceToAdd,
77 // map particle-level parallelism to 1D CUDA thread and block index
78 const int threadIndex = blockIdx.x * blockDim.x + threadIdx.x;
80 // perform addition for each particle
81 if (threadIndex < numAtoms)
84 float3* gm_fDest = &gm_fTotal[threadIndex];
87 // Accumulate or set nbnxm force
91 temp += gm_nbnxmForce[gm_cell[threadIndex]];
95 temp = gm_nbnxmForce[gm_cell[threadIndex]];
100 temp += rvecForceToAdd[threadIndex];
108 GpuForceReduction::Impl::Impl(const DeviceContext& deviceContext, const DeviceStream& deviceStream) :
109 deviceContext_(deviceContext),
110 deviceStream_(deviceStream){};
112 void GpuForceReduction::Impl::reinit(float3* baseForcePtr,
114 ArrayRef<const int> cell,
116 const bool accumulate,
117 GpuEventSynchronizer* completionMarker)
119 GMX_ASSERT((baseForcePtr != nullptr), "Input base force for reduction has no data");
120 baseForce_ = &(baseForcePtr[atomStart]);
121 numAtoms_ = numAtoms;
122 atomStart_ = atomStart;
123 accumulate_ = accumulate;
124 completionMarker_ = completionMarker;
125 cellInfo_.cell = cell.data();
126 reallocateDeviceBuffer(&cellInfo_.d_cell, numAtoms_, &cellInfo_.cellSize,
127 &cellInfo_.cellSizeAlloc, deviceContext_);
128 copyToDeviceBuffer(&cellInfo_.d_cell, &(cellInfo_.cell[atomStart]), 0, numAtoms_, deviceStream_,
129 GpuApiCallBehavior::Async, nullptr);
131 dependencyList_.clear();
134 void GpuForceReduction::Impl::registerNbnxmForce(DeviceBuffer<RVec> forcePtr)
136 GMX_ASSERT((forcePtr != nullptr), "Input force for reduction has no data");
137 nbnxmForceToAdd_ = forcePtr;
140 void GpuForceReduction::Impl::registerRvecForce(DeviceBuffer<RVec> forcePtr)
142 GMX_ASSERT((forcePtr != nullptr), "Input force for reduction has no data");
143 rvecForceToAdd_ = forcePtr;
146 void GpuForceReduction::Impl::addDependency(GpuEventSynchronizer* const dependency)
148 dependencyList_.push_back(dependency);
151 void GpuForceReduction::Impl::execute()
159 GMX_ASSERT((nbnxmForceToAdd_ != nullptr), "Nbnxm force for reduction has no data");
161 // Enqueue wait on all dependencies passed
162 for (auto const synchronizer : dependencyList_)
164 synchronizer->enqueueWaitEvent(deviceStream_);
167 float3* d_nbnxmForce = asFloat3(nbnxmForceToAdd_);
168 float3* d_rvecForceToAdd = &(asFloat3(rvecForceToAdd_)[atomStart_]);
170 // Configure and launch kernel
171 KernelLaunchConfig config;
172 config.blockSize[0] = c_threadsPerBlock;
173 config.blockSize[1] = 1;
174 config.blockSize[2] = 1;
175 config.gridSize[0] = ((numAtoms_ + 1) + c_threadsPerBlock - 1) / c_threadsPerBlock;
176 config.gridSize[1] = 1;
177 config.gridSize[2] = 1;
178 config.sharedMemorySize = 0;
180 auto kernelFn = (rvecForceToAdd_ != nullptr)
181 ? (accumulate_ ? reduceKernel<true, true> : reduceKernel<true, false>)
182 : (accumulate_ ? reduceKernel<false, true> : reduceKernel<false, false>);
184 const auto kernelArgs = prepareGpuKernelArguments(kernelFn, config, &d_nbnxmForce, &d_rvecForceToAdd,
185 &baseForce_, &cellInfo_.d_cell, &numAtoms_);
187 launchGpuKernel(kernelFn, config, deviceStream_, nullptr, "Force Reduction", kernelArgs);
189 // Mark that kernel has been launched
190 if (completionMarker_ != nullptr)
192 completionMarker_->markEvent(deviceStream_);
196 GpuForceReduction::Impl::~Impl(){};
198 GpuForceReduction::GpuForceReduction(const DeviceContext& deviceContext, const DeviceStream& deviceStream) :
199 impl_(new Impl(deviceContext, deviceStream))
203 void GpuForceReduction::registerNbnxmForce(void* forcePtr)
205 impl_->registerNbnxmForce(reinterpret_cast<DeviceBuffer<RVec>>(forcePtr));
208 void GpuForceReduction::registerRvecForce(void* forcePtr)
210 impl_->registerRvecForce(reinterpret_cast<DeviceBuffer<RVec>>(forcePtr));
213 void GpuForceReduction::addDependency(GpuEventSynchronizer* const dependency)
215 impl_->addDependency(dependency);
218 void GpuForceReduction::reinit(DeviceBuffer<RVec> baseForcePtr,
220 ArrayRef<const int> cell,
222 const bool accumulate,
223 GpuEventSynchronizer* completionMarker)
225 impl_->reinit(asFloat3(baseForcePtr), numAtoms, cell, atomStart, accumulate, completionMarker);
227 void GpuForceReduction::execute()
232 GpuForceReduction::~GpuForceReduction() = default;