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tools/cub-1.8.0/cub/agent/agent_reduce_by_key.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::AgentReduceByKey implements a stateful abstraction of CUDA thread blocks for participating in device-wide reduce-value-by-key. */ #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 "../block/block_discontinuity.cuh" #include "../iterator/cache_modified_input_iterator.cuh" #include "../iterator/constant_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 AgentReduceByKey */ 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 BlockScanAlgorithm _SCAN_ALGORITHM> ///< The BlockScan algorithm to use struct AgentReduceByKeyPolicy { 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 BlockScanAlgorithm SCAN_ALGORITHM = _SCAN_ALGORITHM; ///< The BlockScan algorithm to use }; /****************************************************************************** * Thread block abstractions ******************************************************************************/ /** * \brief AgentReduceByKey implements a stateful abstraction of CUDA thread blocks for participating in device-wide reduce-value-by-key */ template < typename AgentReduceByKeyPolicyT, ///< Parameterized AgentReduceByKeyPolicy tuning policy type typename KeysInputIteratorT, ///< Random-access input iterator type for keys typename UniqueOutputIteratorT, ///< Random-access output iterator type for keys typename ValuesInputIteratorT, ///< Random-access input iterator type for values typename AggregatesOutputIteratorT, ///< Random-access output iterator type for values typename NumRunsOutputIteratorT, ///< Output iterator type for recording number of items selected typename EqualityOpT, ///< KeyT equality operator type typename ReductionOpT, ///< ValueT reduction operator type typename OffsetT> ///< Signed integer type for global offsets struct AgentReduceByKey { //--------------------------------------------------------------------- // Types and constants //--------------------------------------------------------------------- // The input keys type typedef typename std::iterator_traits<KeysInputIteratorT>::value_type KeyInputT; // The output keys type typedef typename If<(Equals<typename std::iterator_traits<UniqueOutputIteratorT>::value_type, void>::VALUE), // KeyOutputT = (if output iterator's value type is void) ? typename std::iterator_traits<KeysInputIteratorT>::value_type, // ... then the input iterator's value type, typename std::iterator_traits<UniqueOutputIteratorT>::value_type>::Type KeyOutputT; // ... else the output iterator's value type // The input values type typedef typename std::iterator_traits<ValuesInputIteratorT>::value_type ValueInputT; // The output values type typedef typename If<(Equals<typename std::iterator_traits<AggregatesOutputIteratorT>::value_type, void>::VALUE), // ValueOutputT = (if output iterator's value type is void) ? typename std::iterator_traits<ValuesInputIteratorT>::value_type, // ... then the input iterator's value type, typename std::iterator_traits<AggregatesOutputIteratorT>::value_type>::Type ValueOutputT; // ... else the output iterator's value type // Tuple type for scanning (pairs accumulated segment-value with segment-index) typedef KeyValuePair<OffsetT, ValueOutputT> OffsetValuePairT; // Tuple type for pairing keys and values typedef KeyValuePair<KeyOutputT, ValueOutputT> KeyValuePairT; // Tile status descriptor interface type typedef ReduceByKeyScanTileState<ValueOutputT, OffsetT> ScanTileStateT; // Guarded inequality functor template <typename _EqualityOpT> struct GuardedInequalityWrapper { _EqualityOpT op; ///< Wrapped equality operator int num_remaining; ///< Items remaining /// Constructor __host__ __device__ __forceinline__ GuardedInequalityWrapper(_EqualityOpT op, int num_remaining) : op(op), num_remaining(num_remaining) {} /// Boolean inequality operator, returns <tt>(a != b)</tt> template <typename T> __host__ __device__ __forceinline__ bool operator()(const T &a, const T &b, int idx) const { if (idx < num_remaining) return !op(a, b); // In bounds // Return true if first out-of-bounds item, false otherwise return (idx == num_remaining); } }; // Constants enum { BLOCK_THREADS = AgentReduceByKeyPolicyT::BLOCK_THREADS, ITEMS_PER_THREAD = AgentReduceByKeyPolicyT::ITEMS_PER_THREAD, TILE_ITEMS = BLOCK_THREADS * ITEMS_PER_THREAD, TWO_PHASE_SCATTER = (ITEMS_PER_THREAD > 1), // Whether or not the scan operation has a zero-valued identity value (true if we're performing addition on a primitive type) HAS_IDENTITY_ZERO = (Equals<ReductionOpT, cub::Sum>::VALUE) && (Traits<ValueOutputT>::PRIMITIVE), }; // Cache-modified Input iterator wrapper type (for applying cache modifier) for keys typedef typename If<IsPointer<KeysInputIteratorT>::VALUE, CacheModifiedInputIterator<AgentReduceByKeyPolicyT::LOAD_MODIFIER, KeyInputT, OffsetT>, // Wrap the native input pointer with CacheModifiedValuesInputIterator KeysInputIteratorT>::Type // Directly use the supplied input iterator type WrappedKeysInputIteratorT; // Cache-modified Input iterator wrapper type (for applying cache modifier) for values typedef typename If<IsPointer<ValuesInputIteratorT>::VALUE, CacheModifiedInputIterator<AgentReduceByKeyPolicyT::LOAD_MODIFIER, ValueInputT, OffsetT>, // Wrap the native input pointer with CacheModifiedValuesInputIterator ValuesInputIteratorT>::Type // Directly use the supplied input iterator type WrappedValuesInputIteratorT; // Cache-modified Input iterator wrapper type (for applying cache modifier) for fixup values typedef typename If<IsPointer<AggregatesOutputIteratorT>::VALUE, CacheModifiedInputIterator<AgentReduceByKeyPolicyT::LOAD_MODIFIER, ValueInputT, OffsetT>, // Wrap the native input pointer with CacheModifiedValuesInputIterator AggregatesOutputIteratorT>::Type // Directly use the supplied input iterator type WrappedFixupInputIteratorT; // Reduce-value-by-segment scan operator typedef ReduceBySegmentOp<ReductionOpT> ReduceBySegmentOpT; // Parameterized BlockLoad type for keys typedef BlockLoad< KeyOutputT, BLOCK_THREADS, ITEMS_PER_THREAD, AgentReduceByKeyPolicyT::LOAD_ALGORITHM> BlockLoadKeysT; // Parameterized BlockLoad type for values typedef BlockLoad< ValueOutputT, BLOCK_THREADS, ITEMS_PER_THREAD, AgentReduceByKeyPolicyT::LOAD_ALGORITHM> BlockLoadValuesT; // Parameterized BlockDiscontinuity type for keys typedef BlockDiscontinuity< KeyOutputT, BLOCK_THREADS> BlockDiscontinuityKeys; // Parameterized BlockScan type typedef BlockScan< OffsetValuePairT, BLOCK_THREADS, AgentReduceByKeyPolicyT::SCAN_ALGORITHM> BlockScanT; // Callback type for obtaining tile prefix during block scan typedef TilePrefixCallbackOp< OffsetValuePairT, ReduceBySegmentOpT, ScanTileStateT> TilePrefixCallbackOpT; // Key and value exchange types typedef KeyOutputT KeyExchangeT[TILE_ITEMS + 1]; typedef ValueOutputT ValueExchangeT[TILE_ITEMS + 1]; // Shared memory type for this thread block union _TempStorage { struct { typename BlockScanT::TempStorage scan; // Smem needed for tile scanning typename TilePrefixCallbackOpT::TempStorage prefix; // Smem needed for cooperative prefix callback typename BlockDiscontinuityKeys::TempStorage discontinuity; // Smem needed for discontinuity detection }; // Smem needed for loading keys typename BlockLoadKeysT::TempStorage load_keys; // Smem needed for loading values typename BlockLoadValuesT::TempStorage load_values; // Smem needed for compacting key value pairs(allows non POD items in this union) Uninitialized<KeyValuePairT[TILE_ITEMS + 1]> raw_exchange; }; // Alias wrapper allowing storage to be unioned struct TempStorage : Uninitialized<_TempStorage> {}; //--------------------------------------------------------------------- // Per-thread fields //--------------------------------------------------------------------- _TempStorage& temp_storage; ///< Reference to temp_storage WrappedKeysInputIteratorT d_keys_in; ///< Input keys UniqueOutputIteratorT d_unique_out; ///< Unique output keys WrappedValuesInputIteratorT d_values_in; ///< Input values AggregatesOutputIteratorT d_aggregates_out; ///< Output value aggregates NumRunsOutputIteratorT d_num_runs_out; ///< Output pointer for total number of segments identified EqualityOpT equality_op; ///< KeyT equality operator ReductionOpT reduction_op; ///< Reduction operator ReduceBySegmentOpT scan_op; ///< Reduce-by-segment scan operator //--------------------------------------------------------------------- // Constructor //--------------------------------------------------------------------- // Constructor __device__ __forceinline__ AgentReduceByKey( TempStorage& temp_storage, ///< Reference to temp_storage KeysInputIteratorT d_keys_in, ///< Input keys UniqueOutputIteratorT d_unique_out, ///< Unique output keys ValuesInputIteratorT d_values_in, ///< Input values AggregatesOutputIteratorT d_aggregates_out, ///< Output value aggregates NumRunsOutputIteratorT d_num_runs_out, ///< Output pointer for total number of segments identified EqualityOpT equality_op, ///< KeyT equality operator ReductionOpT reduction_op) ///< ValueT reduction operator : temp_storage(temp_storage.Alias()), d_keys_in(d_keys_in), d_unique_out(d_unique_out), d_values_in(d_values_in), d_aggregates_out(d_aggregates_out), d_num_runs_out(d_num_runs_out), equality_op(equality_op), reduction_op(reduction_op), scan_op(reduction_op) {} //--------------------------------------------------------------------- // Scatter utility methods //--------------------------------------------------------------------- /** * Directly scatter flagged items to output offsets */ __device__ __forceinline__ void ScatterDirect( KeyValuePairT (&scatter_items)[ITEMS_PER_THREAD], OffsetT (&segment_flags)[ITEMS_PER_THREAD], OffsetT (&segment_indices)[ITEMS_PER_THREAD]) { // Scatter flagged keys and values #pragma unroll for (int ITEM = 0; ITEM < ITEMS_PER_THREAD; ++ITEM) { if (segment_flags[ITEM]) { d_unique_out[segment_indices[ITEM]] = scatter_items[ITEM].key; d_aggregates_out[segment_indices[ITEM]] = scatter_items[ITEM].value; } } } /** * 2-phase scatter flagged items to output offsets * * The exclusive scan causes each head flag to be paired with the previous * value aggregate: the scatter offsets must be decremented for value aggregates */ __device__ __forceinline__ void ScatterTwoPhase( KeyValuePairT (&scatter_items)[ITEMS_PER_THREAD], OffsetT (&segment_flags)[ITEMS_PER_THREAD], OffsetT (&segment_indices)[ITEMS_PER_THREAD], OffsetT num_tile_segments, OffsetT num_tile_segments_prefix) { CTA_SYNC(); // Compact and scatter pairs #pragma unroll for (int ITEM = 0; ITEM < ITEMS_PER_THREAD; ++ITEM) { if (segment_flags[ITEM]) { temp_storage.raw_exchange.Alias()[segment_indices[ITEM] - num_tile_segments_prefix] = scatter_items[ITEM]; } } CTA_SYNC(); for (int item = threadIdx.x; item < num_tile_segments; item += BLOCK_THREADS) { KeyValuePairT pair = temp_storage.raw_exchange.Alias()[item]; d_unique_out[num_tile_segments_prefix + item] = pair.key; d_aggregates_out[num_tile_segments_prefix + item] = pair.value; } } /** * Scatter flagged items */ __device__ __forceinline__ void Scatter( KeyValuePairT (&scatter_items)[ITEMS_PER_THREAD], OffsetT (&segment_flags)[ITEMS_PER_THREAD], OffsetT (&segment_indices)[ITEMS_PER_THREAD], OffsetT num_tile_segments, OffsetT num_tile_segments_prefix) { // Do a one-phase scatter if (a) two-phase is disabled or (b) the average number of selected items per thread is less than one if (TWO_PHASE_SCATTER && (num_tile_segments > BLOCK_THREADS)) { ScatterTwoPhase( scatter_items, segment_flags, segment_indices, num_tile_segments, num_tile_segments_prefix); } else { ScatterDirect( scatter_items, segment_flags, segment_indices); } } //--------------------------------------------------------------------- // 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 { KeyOutputT keys[ITEMS_PER_THREAD]; // Tile keys KeyOutputT prev_keys[ITEMS_PER_THREAD]; // Tile keys shuffled up ValueOutputT values[ITEMS_PER_THREAD]; // Tile values OffsetT head_flags[ITEMS_PER_THREAD]; // Segment head flags OffsetT segment_indices[ITEMS_PER_THREAD]; // Segment indices OffsetValuePairT scan_items[ITEMS_PER_THREAD]; // Zipped values and segment flags|indices KeyValuePairT scatter_items[ITEMS_PER_THREAD]; // Zipped key value pairs for scattering // Load keys if (IS_LAST_TILE) BlockLoadKeysT(temp_storage.load_keys).Load(d_keys_in + tile_offset, keys, num_remaining); else BlockLoadKeysT(temp_storage.load_keys).Load(d_keys_in + tile_offset, keys); // Load tile predecessor key in first thread KeyOutputT tile_predecessor; if (threadIdx.x == 0) { tile_predecessor = (tile_idx == 0) ? keys[0] : // First tile gets repeat of first item (thus first item will not be flagged as a head) d_keys_in[tile_offset - 1]; // Subsequent tiles get last key from previous tile } CTA_SYNC(); // Load values if (IS_LAST_TILE) BlockLoadValuesT(temp_storage.load_values).Load(d_values_in + tile_offset, values, num_remaining); else BlockLoadValuesT(temp_storage.load_values).Load(d_values_in + tile_offset, values); CTA_SYNC(); // Initialize head-flags and shuffle up the previous keys if (IS_LAST_TILE) { // Use custom flag operator to additionally flag the first out-of-bounds item GuardedInequalityWrapper<EqualityOpT> flag_op(equality_op, num_remaining); BlockDiscontinuityKeys(temp_storage.discontinuity).FlagHeads( head_flags, keys, prev_keys, flag_op, tile_predecessor); } else { InequalityWrapper<EqualityOpT> flag_op(equality_op); BlockDiscontinuityKeys(temp_storage.discontinuity).FlagHeads( head_flags, keys, prev_keys, flag_op, tile_predecessor); } // Zip values and head flags #pragma unroll for (int ITEM = 0; ITEM < ITEMS_PER_THREAD; ++ITEM) { scan_items[ITEM].value = values[ITEM]; scan_items[ITEM].key = head_flags[ITEM]; } // Perform exclusive tile scan OffsetValuePairT block_aggregate; // Inclusive block-wide scan aggregate OffsetT num_segments_prefix; // Number of segments prior to this tile OffsetValuePairT total_aggregate; // The tile prefix folded with block_aggregate if (tile_idx == 0) { // Scan first tile BlockScanT(temp_storage.scan).ExclusiveScan(scan_items, scan_items, scan_op, block_aggregate); num_segments_prefix = 0; total_aggregate = block_aggregate; // Update tile status if there are successor tiles 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); BlockScanT(temp_storage.scan).ExclusiveScan(scan_items, scan_items, scan_op, prefix_op); block_aggregate = prefix_op.GetBlockAggregate(); num_segments_prefix = prefix_op.GetExclusivePrefix().key; total_aggregate = prefix_op.GetInclusivePrefix(); } // Rezip scatter items and segment indices #pragma unroll for (int ITEM = 0; ITEM < ITEMS_PER_THREAD; ++ITEM) { scatter_items[ITEM].key = prev_keys[ITEM]; scatter_items[ITEM].value = scan_items[ITEM].value; segment_indices[ITEM] = scan_items[ITEM].key; } // At this point, each flagged segment head has: // - The key for the previous segment // - The reduced value from the previous segment // - The segment index for the reduced value // Scatter flagged keys and values OffsetT num_tile_segments = block_aggregate.key; Scatter(scatter_items, head_flags, segment_indices, num_tile_segments, num_segments_prefix); // Last thread in last tile will output final count (and last pair, if necessary) if ((IS_LAST_TILE) && (threadIdx.x == BLOCK_THREADS - 1)) { OffsetT num_segments = num_segments_prefix + num_tile_segments; // If the last tile is a whole tile, output the final_value if (num_remaining == TILE_ITEMS) { d_unique_out[num_segments] = keys[ITEMS_PER_THREAD - 1]; d_aggregates_out[num_segments] = total_aggregate.value; num_segments++; } // Output the total number of items selected *d_num_runs_out = num_segments; } } /** * 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); } } }; } // CUB namespace CUB_NS_POSTFIX // Optional outer namespace(s) |