cub/grid/grid_barrier.cuh
File members: cub/grid/grid_barrier.cuh
/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
* Copyright (c) 2011-2018, NVIDIA CORPORATION. All rights reserved.
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#pragma once
#include <cub/config.cuh>
#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
# pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
# pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
# pragma system_header
#endif // no system header
#include <cub/thread/thread_load.cuh>
#include <cub/util_debug.cuh>
CUB_NAMESPACE_BEGIN
class GridBarrier
{
protected:
using SyncFlag = unsigned int;
// Counters in global device memory
SyncFlag* d_sync;
public:
GridBarrier()
: d_sync(nullptr)
{}
_CCCL_DEVICE _CCCL_FORCEINLINE void Sync() const
{
volatile SyncFlag* d_vol_sync = d_sync;
// Threadfence and syncthreads to make sure global writes are visible before
// thread-0 reports in with its sync counter
__threadfence();
CTA_SYNC();
if (blockIdx.x == 0)
{
// Report in ourselves
if (threadIdx.x == 0)
{
d_vol_sync[blockIdx.x] = 1;
}
CTA_SYNC();
// Wait for everyone else to report in
for (int peer_block = threadIdx.x; peer_block < gridDim.x; peer_block += blockDim.x)
{
while (ThreadLoad<LOAD_CG>(d_sync + peer_block) == 0)
{
__threadfence_block();
}
}
CTA_SYNC();
// Let everyone know it's safe to proceed
for (int peer_block = threadIdx.x; peer_block < gridDim.x; peer_block += blockDim.x)
{
d_vol_sync[peer_block] = 0;
}
}
else
{
if (threadIdx.x == 0)
{
// Report in
d_vol_sync[blockIdx.x] = 1;
// Wait for acknowledgment
while (ThreadLoad<LOAD_CG>(d_sync + blockIdx.x) == 1)
{
__threadfence_block();
}
}
CTA_SYNC();
}
}
};
class GridBarrierLifetime : public GridBarrier
{
protected:
// Number of bytes backed by d_sync
size_t sync_bytes;
public:
GridBarrierLifetime()
: GridBarrier()
, sync_bytes(0)
{}
cudaError_t HostReset()
{
cudaError_t retval = cudaSuccess;
if (d_sync)
{
retval = CubDebug(cudaFree(d_sync));
d_sync = nullptr;
}
sync_bytes = 0;
return retval;
}
virtual ~GridBarrierLifetime()
{
HostReset();
}
cudaError_t Setup(int sweep_grid_size)
{
cudaError_t retval = cudaSuccess;
do
{
size_t new_sync_bytes = sweep_grid_size * sizeof(SyncFlag);
if (new_sync_bytes > sync_bytes)
{
if (d_sync)
{
retval = CubDebug(cudaFree(d_sync));
if (cudaSuccess != retval)
{
break;
}
}
sync_bytes = new_sync_bytes;
// Allocate and initialize to zero
retval = CubDebug(cudaMalloc((void**) &d_sync, sync_bytes));
if (cudaSuccess != retval)
{
break;
}
retval = CubDebug(cudaMemset(d_sync, 0, new_sync_bytes));
if (cudaSuccess != retval)
{
break;
}
}
} while (0);
return retval;
}
};
CUB_NAMESPACE_END