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tools/cub-1.8.0/cub/agent/agent_reduce_by_key.cuh 24.2 KB
8dcb6dfcb   Yannick Estève   first commit
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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)