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tools/cub-1.8.0/cub/agent/agent_scan.cuh
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/******************************************************************************
* Copyright (c) 2011, Duane Merrill. All rights reserved.
* Copyright (c) 2011-2018, 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::AgentScan implements a stateful abstraction of CUDA thread blocks for participating in device-wide prefix scan .
*/
#pragma once
#include <iterator>
#include "single_pass_scan_operators.cuh"
#include "../block/block_load.cuh"
#include "../block/block_store.cuh"
#include "../block/block_scan.cuh"
#include "../grid/grid_queue.cuh"
#include "../iterator/cache_modified_input_iterator.cuh"
#include "../util_namespace.cuh"
/// Optional outer namespace(s)
CUB_NS_PREFIX
/// CUB namespace
namespace cub {
/******************************************************************************
* Tuning policy types
******************************************************************************/
/**
* Parameterizable tuning policy type for AgentScan
*/
template <
int _BLOCK_THREADS, ///< Threads per thread block
int _ITEMS_PER_THREAD, ///< Items per thread (per tile of input)
BlockLoadAlgorithm _LOAD_ALGORITHM, ///< The BlockLoad algorithm to use
CacheLoadModifier _LOAD_MODIFIER, ///< Cache load modifier for reading input elements
BlockStoreAlgorithm _STORE_ALGORITHM, ///< The BlockStore algorithm to use
BlockScanAlgorithm _SCAN_ALGORITHM> ///< The BlockScan algorithm to use
struct AgentScanPolicy
{
enum
{
BLOCK_THREADS = _BLOCK_THREADS, ///< Threads per thread block
ITEMS_PER_THREAD = _ITEMS_PER_THREAD, ///< Items per thread (per tile of input)
};
static const BlockLoadAlgorithm LOAD_ALGORITHM = _LOAD_ALGORITHM; ///< The BlockLoad algorithm to use
static const CacheLoadModifier LOAD_MODIFIER = _LOAD_MODIFIER; ///< Cache load modifier for reading input elements
static const BlockStoreAlgorithm STORE_ALGORITHM = _STORE_ALGORITHM; ///< The BlockStore algorithm to use
static const BlockScanAlgorithm SCAN_ALGORITHM = _SCAN_ALGORITHM; ///< The BlockScan algorithm to use
};
/******************************************************************************
* Thread block abstractions
******************************************************************************/
/**
* \brief AgentScan implements a stateful abstraction of CUDA thread blocks for participating in device-wide prefix scan .
*/
template <
typename AgentScanPolicyT, ///< Parameterized AgentScanPolicyT tuning policy type
typename InputIteratorT, ///< Random-access input iterator type
typename OutputIteratorT, ///< Random-access output iterator type
typename ScanOpT, ///< Scan functor type
typename InitValueT, ///< The init_value element for ScanOpT type (cub::NullType for inclusive scan)
typename OffsetT> ///< Signed integer type for global offsets
struct AgentScan
{
//---------------------------------------------------------------------
// Types and constants
//---------------------------------------------------------------------
// The input value type
typedef typename std::iterator_traits<InputIteratorT>::value_type InputT;
// The output value type
typedef typename If<(Equals<typename std::iterator_traits<OutputIteratorT>::value_type, void>::VALUE), // OutputT = (if output iterator's value type is void) ?
typename std::iterator_traits<InputIteratorT>::value_type, // ... then the input iterator's value type,
typename std::iterator_traits<OutputIteratorT>::value_type>::Type OutputT; // ... else the output iterator's value type
// Tile status descriptor interface type
typedef ScanTileState<OutputT> ScanTileStateT;
// Input iterator wrapper type (for applying cache modifier)
typedef typename If<IsPointer<InputIteratorT>::VALUE,
CacheModifiedInputIterator<AgentScanPolicyT::LOAD_MODIFIER, InputT, OffsetT>, // Wrap the native input pointer with CacheModifiedInputIterator
InputIteratorT>::Type // Directly use the supplied input iterator type
WrappedInputIteratorT;
// Constants
enum
{
IS_INCLUSIVE = Equals<InitValueT, NullType>::VALUE, // Inclusive scan if no init_value type is provided
BLOCK_THREADS = AgentScanPolicyT::BLOCK_THREADS,
ITEMS_PER_THREAD = AgentScanPolicyT::ITEMS_PER_THREAD,
TILE_ITEMS = BLOCK_THREADS * ITEMS_PER_THREAD,
};
// Parameterized BlockLoad type
typedef BlockLoad<
OutputT,
AgentScanPolicyT::BLOCK_THREADS,
AgentScanPolicyT::ITEMS_PER_THREAD,
AgentScanPolicyT::LOAD_ALGORITHM>
BlockLoadT;
// Parameterized BlockStore type
typedef BlockStore<
OutputT,
AgentScanPolicyT::BLOCK_THREADS,
AgentScanPolicyT::ITEMS_PER_THREAD,
AgentScanPolicyT::STORE_ALGORITHM>
BlockStoreT;
// Parameterized BlockScan type
typedef BlockScan<
OutputT,
AgentScanPolicyT::BLOCK_THREADS,
AgentScanPolicyT::SCAN_ALGORITHM>
BlockScanT;
// Callback type for obtaining tile prefix during block scan
typedef TilePrefixCallbackOp<
OutputT,
ScanOpT,
ScanTileStateT>
TilePrefixCallbackOpT;
// Stateful BlockScan prefix callback type for managing a running total while scanning consecutive tiles
typedef BlockScanRunningPrefixOp<
OutputT,
ScanOpT>
RunningPrefixCallbackOp;
// Shared memory type for this thread block
union _TempStorage
{
typename BlockLoadT::TempStorage load; // Smem needed for tile loading
typename BlockStoreT::TempStorage store; // Smem needed for tile storing
struct
{
typename TilePrefixCallbackOpT::TempStorage prefix; // Smem needed for cooperative prefix callback
typename BlockScanT::TempStorage scan; // Smem needed for tile scanning
};
};
// Alias wrapper allowing storage to be unioned
struct TempStorage : Uninitialized<_TempStorage> {};
//---------------------------------------------------------------------
// Per-thread fields
//---------------------------------------------------------------------
_TempStorage& temp_storage; ///< Reference to temp_storage
WrappedInputIteratorT d_in; ///< Input data
OutputIteratorT d_out; ///< Output data
ScanOpT scan_op; ///< Binary scan operator
InitValueT init_value; ///< The init_value element for ScanOpT
//---------------------------------------------------------------------
// Block scan utility methods
//---------------------------------------------------------------------
/**
* Exclusive scan specialization (first tile)
*/
__device__ __forceinline__
void ScanTile(
OutputT (&items)[ITEMS_PER_THREAD],
OutputT init_value,
ScanOpT scan_op,
OutputT &block_aggregate,
Int2Type<false> /*is_inclusive*/)
{
BlockScanT(temp_storage.scan).ExclusiveScan(items, items, init_value, scan_op, block_aggregate);
block_aggregate = scan_op(init_value, block_aggregate);
}
/**
* Inclusive scan specialization (first tile)
*/
__device__ __forceinline__
void ScanTile(
OutputT (&items)[ITEMS_PER_THREAD],
InitValueT /*init_value*/,
ScanOpT scan_op,
OutputT &block_aggregate,
Int2Type<true> /*is_inclusive*/)
{
BlockScanT(temp_storage.scan).InclusiveScan(items, items, scan_op, block_aggregate);
}
/**
* Exclusive scan specialization (subsequent tiles)
*/
template <typename PrefixCallback>
__device__ __forceinline__
void ScanTile(
OutputT (&items)[ITEMS_PER_THREAD],
ScanOpT scan_op,
PrefixCallback &prefix_op,
Int2Type<false> /*is_inclusive*/)
{
BlockScanT(temp_storage.scan).ExclusiveScan(items, items, scan_op, prefix_op);
}
/**
* Inclusive scan specialization (subsequent tiles)
*/
template <typename PrefixCallback>
__device__ __forceinline__
void ScanTile(
OutputT (&items)[ITEMS_PER_THREAD],
ScanOpT scan_op,
PrefixCallback &prefix_op,
Int2Type<true> /*is_inclusive*/)
{
BlockScanT(temp_storage.scan).InclusiveScan(items, items, scan_op, prefix_op);
}
//---------------------------------------------------------------------
// Constructor
//---------------------------------------------------------------------
// Constructor
__device__ __forceinline__
AgentScan(
TempStorage& temp_storage, ///< Reference to temp_storage
InputIteratorT d_in, ///< Input data
OutputIteratorT d_out, ///< Output data
ScanOpT scan_op, ///< Binary scan operator
InitValueT init_value) ///< Initial value to seed the exclusive scan
:
temp_storage(temp_storage.Alias()),
d_in(d_in),
d_out(d_out),
scan_op(scan_op),
init_value(init_value)
{}
//---------------------------------------------------------------------
// Cooperatively scan a device-wide sequence of tiles with other CTAs
//---------------------------------------------------------------------
/**
* Process a tile of input (dynamic chained scan)
*/
template <bool IS_LAST_TILE> ///< Whether the current tile is the last tile
__device__ __forceinline__ void ConsumeTile(
OffsetT num_remaining, ///< Number of global input items remaining (including this tile)
int tile_idx, ///< Tile index
OffsetT tile_offset, ///< Tile offset
ScanTileStateT& tile_state) ///< Global tile state descriptor
{
// Load items
OutputT items[ITEMS_PER_THREAD];
if (IS_LAST_TILE)
BlockLoadT(temp_storage.load).Load(d_in + tile_offset, items, num_remaining);
else
BlockLoadT(temp_storage.load).Load(d_in + tile_offset, items);
CTA_SYNC();
// Perform tile scan
if (tile_idx == 0)
{
// Scan first tile
OutputT block_aggregate;
ScanTile(items, init_value, scan_op, block_aggregate, Int2Type<IS_INCLUSIVE>());
if ((!IS_LAST_TILE) && (threadIdx.x == 0))
tile_state.SetInclusive(0, block_aggregate);
}
else
{
// Scan non-first tile
TilePrefixCallbackOpT prefix_op(tile_state, temp_storage.prefix, scan_op, tile_idx);
ScanTile(items, scan_op, prefix_op, Int2Type<IS_INCLUSIVE>());
}
CTA_SYNC();
// Store items
if (IS_LAST_TILE)
BlockStoreT(temp_storage.store).Store(d_out + tile_offset, items, num_remaining);
else
BlockStoreT(temp_storage.store).Store(d_out + tile_offset, items);
}
/**
* Scan tiles of items as part of a dynamic chained scan
*/
__device__ __forceinline__ void ConsumeRange(
int num_items, ///< Total number of input items
ScanTileStateT& tile_state, ///< Global tile state descriptor
int start_tile) ///< The starting tile for the current grid
{
// Blocks are launched in increasing order, so just assign one tile per block
int tile_idx = start_tile + blockIdx.x; // Current tile index
OffsetT tile_offset = OffsetT(TILE_ITEMS) * tile_idx; // Global offset for the current tile
OffsetT num_remaining = num_items - tile_offset; // Remaining items (including this tile)
if (num_remaining > TILE_ITEMS)
{
// Not last tile
ConsumeTile<false>(num_remaining, tile_idx, tile_offset, tile_state);
}
else if (num_remaining > 0)
{
// Last tile
ConsumeTile<true>(num_remaining, tile_idx, tile_offset, tile_state);
}
}
//---------------------------------------------------------------------
// Scan an sequence of consecutive tiles (independent of other thread blocks)
//---------------------------------------------------------------------
/**
* Process a tile of input
*/
template <
bool IS_FIRST_TILE,
bool IS_LAST_TILE>
__device__ __forceinline__ void ConsumeTile(
OffsetT tile_offset, ///< Tile offset
RunningPrefixCallbackOp& prefix_op, ///< Running prefix operator
int valid_items = TILE_ITEMS) ///< Number of valid items in the tile
{
// Load items
OutputT items[ITEMS_PER_THREAD];
if (IS_LAST_TILE)
BlockLoadT(temp_storage.load).Load(d_in + tile_offset, items, valid_items);
else
BlockLoadT(temp_storage.load).Load(d_in + tile_offset, items);
CTA_SYNC();
// Block scan
if (IS_FIRST_TILE)
{
OutputT block_aggregate;
ScanTile(items, init_value, scan_op, block_aggregate, Int2Type<IS_INCLUSIVE>());
prefix_op.running_total = block_aggregate;
}
else
{
ScanTile(items, scan_op, prefix_op, Int2Type<IS_INCLUSIVE>());
}
CTA_SYNC();
// Store items
if (IS_LAST_TILE)
BlockStoreT(temp_storage.store).Store(d_out + tile_offset, items, valid_items);
else
BlockStoreT(temp_storage.store).Store(d_out + tile_offset, items);
}
/**
* Scan a consecutive share of input tiles
*/
__device__ __forceinline__ void ConsumeRange(
OffsetT range_offset, ///< [in] Threadblock begin offset (inclusive)
OffsetT range_end) ///< [in] Threadblock end offset (exclusive)
{
BlockScanRunningPrefixOp<OutputT, ScanOpT> prefix_op(scan_op);
if (range_offset + TILE_ITEMS <= range_end)
{
// Consume first tile of input (full)
ConsumeTile<true, true>(range_offset, prefix_op);
range_offset += TILE_ITEMS;
// Consume subsequent full tiles of input
while (range_offset + TILE_ITEMS <= range_end)
{
ConsumeTile<false, true>(range_offset, prefix_op);
range_offset += TILE_ITEMS;
}
// Consume a partially-full tile
if (range_offset < range_end)
{
int valid_items = range_end - range_offset;
ConsumeTile<false, false>(range_offset, prefix_op, valid_items);
}
}
else
{
// Consume the first tile of input (partially-full)
int valid_items = range_end - range_offset;
ConsumeTile<true, false>(range_offset, prefix_op, valid_items);
}
}
/**
* Scan a consecutive share of input tiles, seeded with the specified prefix value
*/
__device__ __forceinline__ void ConsumeRange(
OffsetT range_offset, ///< [in] Threadblock begin offset (inclusive)
OffsetT range_end, ///< [in] Threadblock end offset (exclusive)
OutputT prefix) ///< [in] The prefix to apply to the scan segment
{
BlockScanRunningPrefixOp<OutputT, ScanOpT> prefix_op(prefix, scan_op);
// Consume full tiles of input
while (range_offset + TILE_ITEMS <= range_end)
{
ConsumeTile<true, false>(range_offset, prefix_op);
range_offset += TILE_ITEMS;
}
// Consume a partially-full tile
if (range_offset < range_end)
{
int valid_items = range_end - range_offset;
ConsumeTile<false, false>(range_offset, prefix_op, valid_items);
}
}
};
} // CUB namespace
CUB_NS_POSTFIX // Optional outer namespace(s)
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