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grid_barrier.cuh
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/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
* Copyright (c) 2011-2013, NVIDIA CORPORATION. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the NVIDIA CORPORATION nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************/
/**
* \file
* cub::GridBarrier implements a software global barrier among thread blocks within a CUDA grid
*/
#pragma once
#include "../util_debug.cuh"
#include "../util_namespace.cuh"
#include "../thread/thread_load.cuh"
/// Optional outer namespace(s)
CUB_NS_PREFIX
/// CUB namespace
namespace cub {
/**
* \addtogroup GridModule
* @{
*/
/**
* \brief GridBarrier implements a software global barrier among thread blocks within a CUDA grid
*/
class GridBarrier
{
protected :
typedef unsigned int SyncFlag;
// Counters in global device memory
SyncFlag* d_sync;
public:
/**
* Constructor
*/
GridBarrier() : d_sync(NULL) {}
/**
* Synchronize
*/
__device__ __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();
__syncthreads();
if (blockIdx.x == 0)
{
// Report in ourselves
if (threadIdx.x == 0)
{
d_vol_sync[blockIdx.x] = 1;
}
__syncthreads();
// 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();
}
}
__syncthreads();
// 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();
}
}
__syncthreads();
}
}
};
/**
* \brief GridBarrierLifetime extends GridBarrier to provide lifetime management of the temporary device storage needed for cooperation.
*
* Uses RAII for lifetime, i.e., device resources are reclaimed when
* the destructor is called.
*/
class GridBarrierLifetime : public GridBarrier
{
protected:
// Number of bytes backed by d_sync
size_t sync_bytes;
public:
/**
* Constructor
*/
GridBarrierLifetime() : GridBarrier(), sync_bytes(0) {}
/**
* DeviceFrees and resets the progress counters
*/
cudaError_t HostReset()
{
cudaError_t retval = cudaSuccess;
if (d_sync)
{
CubDebug(retval = cudaFree(d_sync));
d_sync = NULL;
}
sync_bytes = 0;
return retval;
}
/**
* Destructor
*/
virtual ~GridBarrierLifetime()
{
HostReset();
}
/**
* Sets up the progress counters for the next kernel launch (lazily
* allocating and initializing them if necessary)
*/
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)
{
if (CubDebug(retval = cudaFree(d_sync))) break;
}
sync_bytes = new_sync_bytes;
// Allocate and initialize to zero
if (CubDebug(retval = cudaMalloc((void**) &d_sync, sync_bytes))) break;
if (CubDebug(retval = cudaMemset(d_sync, 0, new_sync_bytes))) break;
}
} while (0);
return retval;
}
};
/** @} */ // end group GridModule
} // CUB namespace
CUB_NS_POSTFIX // Optional outer namespace(s)

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