| /****************************************************************************** |
| * Copyright (c) 2011, Duane Merrill. All rights reserved. |
| * Copyright (c) 2011-2018, NVIDIA CORPORATION. All rights reserved. |
| * |
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| * derived from this software without specific prior written permission. |
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| |
| /** |
| * @file |
| * The cub::BlockDiscontinuity class provides [<em>collective</em>](index.html#sec0) methods for |
| * flagging discontinuities within an ordered set of items partitioned across a CUDA thread block. |
| */ |
| |
| #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/util_ptx.cuh> |
| #include <cub/util_type.cuh> |
| |
| CUB_NAMESPACE_BEGIN |
| |
| /** |
| * @brief The BlockDiscontinuity class provides [<em>collective</em>](index.html#sec0) methods for |
| * flagging discontinuities within an ordered set of items partitioned across a CUDA thread |
| * block.  |
| * |
| * @ingroup BlockModule |
| * |
| * @tparam T |
| * The data type to be flagged. |
| * |
| * @tparam BLOCK_DIM_X |
| * The thread block length in threads along the X dimension |
| * |
| * @tparam BLOCK_DIM_Y |
| * <b>[optional]</b> The thread block length in threads along the Y dimension (default: 1) |
| * |
| * @tparam BLOCK_DIM_Z |
| * <b>[optional]</b> The thread block length in threads along the Z dimension (default: 1) |
| * |
| * @tparam LEGACY_PTX_ARCH |
| * <b>[optional]</b> Unused. |
| * |
| * @par Overview |
| * - A set of "head flags" (or "tail flags") is often used to indicate corresponding items |
| * that differ from their predecessors (or successors). For example, head flags are convenient |
| * for demarcating disjoint data segments as part of a segmented scan or reduction. |
| * - \blocked |
| * |
| * @par Performance Considerations |
| * - \granularity |
| * |
| * @par A Simple Example |
| * \blockcollective{BlockDiscontinuity} |
| * @par |
| * The code snippet below illustrates the head flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Collectively compute head flags for discontinuities in the segment |
| * int head_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagHeads(head_flags, thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input \p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], [3,4,4,4], ... }</tt>. |
| * The corresponding output \p head_flags in those threads will be |
| * <tt>{ [1,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * |
| * @par Performance Considerations |
| * - Incurs zero bank conflicts for most types |
| * |
| * @par Re-using dynamically allocating shared memory |
| * The following example under the examples/block folder illustrates usage of |
| * dynamically shared memory with BlockReduce and how to re-purpose |
| * the same memory region: |
| * <a |
| * href="../../examples/block/example_block_reduce_dyn_smem.cu">example_block_reduce_dyn_smem.cu</a> |
| * |
| * This example can be easily adapted to the storage required by BlockDiscontinuity. |
| */ |
| template < |
| typename T, |
| int BLOCK_DIM_X, |
| int BLOCK_DIM_Y = 1, |
| int BLOCK_DIM_Z = 1, |
| int LEGACY_PTX_ARCH = 0> |
| class BlockDiscontinuity |
| { |
| private: |
| |
| /****************************************************************************** |
| * Constants and type definitions |
| ******************************************************************************/ |
| |
| /// Constants |
| enum |
| { |
| /// The thread block size in threads |
| BLOCK_THREADS = BLOCK_DIM_X * BLOCK_DIM_Y * BLOCK_DIM_Z, |
| }; |
| |
|
|
| /// Shared memory storage layout type (last element from each thread's input) |
| struct _TempStorage |
| { |
| T first_items[BLOCK_THREADS]; |
| T last_items[BLOCK_THREADS]; |
| }; |
| |
|
|
| /****************************************************************************** |
| * Utility methods |
| ******************************************************************************/ |
| |
| /// Internal storage allocator |
| __device__ __forceinline__ _TempStorage& PrivateStorage() |
| { |
| __shared__ _TempStorage private_storage; |
| return private_storage; |
| } |
| |
|
|
| /// Specialization for when FlagOp has third index param |
| template <typename FlagOp, bool HAS_PARAM = BinaryOpHasIdxParam<T, FlagOp>::HAS_PARAM> |
| struct ApplyOp |
| { |
| // Apply flag operator |
| static __device__ __forceinline__ bool FlagT(FlagOp flag_op, const T &a, const T &b, int idx) |
| { |
| return flag_op(a, b, idx); |
| } |
| }; |
| |
| /// Specialization for when FlagOp does not have a third index param |
| template <typename FlagOp> |
| struct ApplyOp<FlagOp, false> |
| { |
| // Apply flag operator |
| static __device__ __forceinline__ bool FlagT(FlagOp flag_op, const T &a, const T &b, int /*idx*/) |
| { |
| return flag_op(a, b); |
| } |
| }; |
| |
| /// Templated unrolling of item comparison (inductive case) |
| struct Iterate |
| { |
| /** |
| * @brief Head flags |
| * |
| * @param[out] flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[out] preds |
| * Calling thread's predecessor items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| static __device__ __forceinline__ void FlagHeads(int linear_tid, |
| FlagT (&flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| T (&preds)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| #pragma unroll |
| for (int i = 1; i < ITEMS_PER_THREAD; ++i) { |
| preds[i] = input[i - 1]; |
| flags[i] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| preds[i], |
| input[i], |
| (linear_tid * ITEMS_PER_THREAD) + i); |
| } |
| } |
| |
| /** |
| * @brief Tail flags |
| * |
| * @param[out] flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| static __device__ __forceinline__ void FlagTails(int linear_tid, |
| FlagT (&flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| #pragma unroll |
| for (int i = 0; i < ITEMS_PER_THREAD - 1; ++i) { |
| flags[i] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[i], |
| input[i + 1], |
| (linear_tid * ITEMS_PER_THREAD) + i + 1); |
| } |
| } |
| |
| }; |
| |
| /****************************************************************************** |
| * Thread fields |
| ******************************************************************************/ |
| |
| /// Shared storage reference |
| _TempStorage &temp_storage; |
| |
| /// Linear thread-id |
| unsigned int linear_tid; |
| |
|
|
| public: |
|
|
| /// @smemstorage{BlockDiscontinuity} |
| struct TempStorage : Uninitialized<_TempStorage> {}; |
| |
|
|
| /******************************************************************//** |
| * @name Collective constructors |
| *********************************************************************/ |
| //@{ |
| |
| /** |
| * @brief Collective constructor using a private static allocation of shared memory as temporary |
| * storage. |
| */ |
| __device__ __forceinline__ BlockDiscontinuity() |
| : |
| temp_storage(PrivateStorage()), |
| linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z)) |
| {} |
| |
| /** |
| * @brief Collective constructor using the specified memory allocation as temporary storage. |
| * |
| * @param[in] temp_storage |
| * Reference to memory allocation having layout type TempStorage |
| */ |
| __device__ __forceinline__ BlockDiscontinuity(TempStorage &temp_storage) |
| : temp_storage(temp_storage.Alias()) |
| , linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z)) |
| {} |
| |
| //@} end member group |
| /******************************************************************//** |
| * \name Head flag operations |
| *********************************************************************/ |
| //@{ |
| |
|
|
| #ifndef DOXYGEN_SHOULD_SKIP_THIS // Do not document |
| |
| /** |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[out] preds |
| * Calling thread's predecessor items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeads(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| T (&preds)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share last item |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| if (linear_tid == 0) |
| { |
| // Set flag for first thread-item (preds[0] is undefined) |
| head_flags[0] = 1; |
| } |
| else |
| { |
| preds[0] = temp_storage.last_items[linear_tid - 1]; |
| head_flags[0] = ApplyOp<FlagOp>::FlagT(flag_op, preds[0], input[0], linear_tid * ITEMS_PER_THREAD); |
| } |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| } |
| |
| /** |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[out] preds |
| * Calling thread's predecessor items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| * |
| * @param[in] tile_predecessor_item |
| * <b>[<em>thread</em><sub>0</sub> only]</b> Item with which to compare the first tile item |
| * (<tt>input<sub>0</sub></tt> from <em>thread</em><sub>0</sub>). |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeads(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| T (&preds)[ITEMS_PER_THREAD], |
| FlagOp flag_op, |
| T tile_predecessor_item) |
| { |
| // Share last item |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| // Set flag for first thread-item |
| preds[0] = (linear_tid == 0) ? |
| tile_predecessor_item : // First thread |
| temp_storage.last_items[linear_tid - 1]; |
| |
| head_flags[0] = ApplyOp<FlagOp>::FlagT(flag_op, preds[0], input[0], linear_tid * ITEMS_PER_THREAD); |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| } |
| |
| #endif // DOXYGEN_SHOULD_SKIP_THIS |
| |
| /** |
| * @brief Sets head flags indicating discontinuities between items partitioned across the thread |
| * block, for which the first item has no reference and is always flagged. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns \p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is always flagged. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Collectively compute head flags for discontinuities in the segment |
| * int head_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagHeads(head_flags, thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input \p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], [3,4,4,4], ... }</tt>. |
| * The corresponding output \p head_flags in those threads will be |
| * <tt>{ [1,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning \p true |
| * if a discontinuity exists between \p a and \p b, otherwise \p false. \p b_index is the rank |
| * of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeads(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| T preds[ITEMS_PER_THREAD]; |
| FlagHeads(head_flags, input, preds, flag_op); |
| } |
| |
| /** |
| * @brief Sets head flags indicating discontinuities between items partitioned across the thread |
| * block. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns \p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is compared |
| * against \p tile_predecessor_item. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Have thread0 obtain the predecessor item for the entire tile |
| * int tile_predecessor_item; |
| * if (threadIdx.x == 0) tile_predecessor_item == ... |
| * |
| * // Collectively compute head flags for discontinuities in the segment |
| * int head_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagHeads( |
| * head_flags, thread_data, cub::Inequality(), tile_predecessor_item); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input \p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], [3,4,4,4], ... }</tt>, |
| * and that \p tile_predecessor_item is \p 0. The corresponding output \p head_flags in those |
| * threads will be <tt>{ [0,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, |
| * and returning \p true if a discontinuity exists between \p a and \p b, |
| * otherwise \p false. \p b_index is the rank of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| * |
| * @param[in] tile_predecessor_item |
| * <b>[<em>thread</em><sub>0</sub> only]</b> Item with which to compare the first tile item |
| * (<tt>input<sub>0</sub></tt> from <em>thread</em><sub>0</sub>). |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeads(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op, |
| T tile_predecessor_item) |
| { |
| T preds[ITEMS_PER_THREAD]; |
| FlagHeads(head_flags, input, preds, flag_op, tile_predecessor_item); |
| } |
| |
|
|
|
|
| //@} end member group |
| /******************************************************************//** |
| * @name Tail flag operations |
| *********************************************************************/ |
| //@{ |
| |
| /** |
| * @brief Sets tail flags indicating discontinuities between items partitioned across the thread |
| * block, for which the last item has no reference and is always flagged. |
| * |
| * @par |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns \p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is always flagged. |
| * - @blocked |
| * - @granularity |
| * - @smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Collectively compute tail flags for discontinuities in the segment |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails(tail_flags, thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt>. |
| * The corresponding output @p tail_flags in those threads will be |
| * <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,1] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning \p true |
| * if a discontinuity exists between \p a and \p b, otherwise \p false. \p b_index is the |
| * rank of b in the aggregate tile of data. |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagTails(FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share first item |
| temp_storage.first_items[linear_tid] = input[0]; |
| |
| CTA_SYNC(); |
| |
| // Set flag for last thread-item |
| tail_flags[ITEMS_PER_THREAD - 1] = (linear_tid == BLOCK_THREADS - 1) ? |
| 1 : // Last thread |
| ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| temp_storage.first_items[linear_tid + 1], |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
| /** |
| * @brief Sets tail flags indicating discontinuities between items partitioned across the thread |
| * block. |
| * |
| * @par |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns @p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is compared |
| * against @p tile_successor_item. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Have thread127 obtain the successor item for the entire tile |
| * int tile_successor_item; |
| * if (threadIdx.x == 127) tile_successor_item == ... |
| * |
| * // Collectively compute tail flags for discontinuities in the segment |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails( |
| * tail_flags, thread_data, cub::Inequality(), tile_successor_item); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt> |
| * and that @p tile_successor_item is @p 125. The corresponding output @p tail_flags in those |
| * threads will be <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,0] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning @p true |
| * if a discontinuity exists between @p a and @p b, otherwise @p false. @p b_index is the |
| * rank of b in the aggregate tile of data. |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| * |
| * @param[in] tile_successor_item |
| * <b>[<em>thread</em><sub><tt>BLOCK_THREADS</tt>-1</sub> only]</b> Item with which to |
| * compare the last tile item (<tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> from |
| * <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>). |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagTails(FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op, |
| T tile_successor_item) |
| { |
| // Share first item |
| temp_storage.first_items[linear_tid] = input[0]; |
| |
| CTA_SYNC(); |
| |
| // Set flag for last thread-item |
| T successor_item = (linear_tid == BLOCK_THREADS - 1) ? |
| tile_successor_item : // Last thread |
| temp_storage.first_items[linear_tid + 1]; |
| |
| tail_flags[ITEMS_PER_THREAD - 1] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| successor_item, |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
|
|
| //@} end member group |
| /******************************************************************//** |
| * @name Head & tail flag operations |
| *********************************************************************/ |
| //@{ |
| |
| /** |
| * @brief Sets both head and tail flags indicating discontinuities between items partitioned |
| * across the thread block. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns @p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is always flagged. |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns @p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is always flagged. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head- and tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Collectively compute head and flags for discontinuities in the segment |
| * int head_flags[4]; |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails( |
| * head_flags, tail_flags, thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt> |
| * and that the tile_successor_item is @p 125. The corresponding output @p head_flags |
| * in those threads will be <tt>{ [1,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * and the corresponding output @p tail_flags in those threads will be |
| * <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,1] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning \p true |
| * if a discontinuity exists between \p a and \p b, otherwise \p false. \p b_index is the |
| * rank of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeadsAndTails(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share first and last items |
| temp_storage.first_items[linear_tid] = input[0]; |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| T preds[ITEMS_PER_THREAD]; |
| |
| // Set flag for first thread-item |
| if (linear_tid == 0) |
| { |
| head_flags[0] = 1; |
| } |
| else |
| { |
| preds[0] = temp_storage.last_items[linear_tid - 1]; |
| head_flags[0] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| preds[0], |
| input[0], |
| linear_tid * ITEMS_PER_THREAD); |
| } |
| |
|
|
| // Set flag for last thread-item |
| tail_flags[ITEMS_PER_THREAD - 1] = (linear_tid == BLOCK_THREADS - 1) ? |
| 1 : // Last thread |
| ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| temp_storage.first_items[linear_tid + 1], |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
| /** |
| * @brief Sets both head and tail flags indicating discontinuities between items partitioned |
| * across the thread block. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns @p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is always flagged. |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns @p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is compared |
| * against @p tile_predecessor_item. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head- and tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Have thread127 obtain the successor item for the entire tile |
| * int tile_successor_item; |
| * if (threadIdx.x == 127) tile_successor_item == ... |
| * |
| * // Collectively compute head and flags for discontinuities in the segment |
| * int head_flags[4]; |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails( |
| * head_flags, tail_flags, tile_successor_item, thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt> |
| * and that the tile_successor_item is @p 125. The corresponding output @p head_flags |
| * in those threads will be <tt>{ [1,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * and the corresponding output @p tail_flags in those threads will be |
| * <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,0] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning @p true |
| * if a discontinuity exists between @p a and @p b, otherwise @p false. @p b_index is the |
| * rank of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] tile_successor_item |
| * <b>[<em>thread</em><sub><tt>BLOCK_THREADS</tt>-1</sub> only]</b> Item with which to compare |
| * the last tile item (<tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> from |
| * <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>). |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeadsAndTails(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T tile_successor_item, |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share first and last items |
| temp_storage.first_items[linear_tid] = input[0]; |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| T preds[ITEMS_PER_THREAD]; |
| |
| // Set flag for first thread-item |
| if (linear_tid == 0) |
| { |
| head_flags[0] = 1; |
| } |
| else |
| { |
| preds[0] = temp_storage.last_items[linear_tid - 1]; |
| head_flags[0] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| preds[0], |
| input[0], |
| linear_tid * ITEMS_PER_THREAD); |
| } |
| |
| // Set flag for last thread-item |
| T successor_item = (linear_tid == BLOCK_THREADS - 1) ? |
| tile_successor_item : // Last thread |
| temp_storage.first_items[linear_tid + 1]; |
| |
| tail_flags[ITEMS_PER_THREAD - 1] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| successor_item, |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
| /** |
| * @brief Sets both head and tail flags indicating discontinuities between items partitioned |
| * across the thread block. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns @p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is compared |
| * against @p tile_predecessor_item. |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns @p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is always flagged. |
| * - \blocked |
| * - \granularity |
| * - \smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head- and tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Have thread0 obtain the predecessor item for the entire tile |
| * int tile_predecessor_item; |
| * if (threadIdx.x == 0) tile_predecessor_item == ... |
| * |
| * // Have thread127 obtain the successor item for the entire tile |
| * int tile_successor_item; |
| * if (threadIdx.x == 127) tile_successor_item == ... |
| * |
| * // Collectively compute head and flags for discontinuities in the segment |
| * int head_flags[4]; |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails( |
| * head_flags, tile_predecessor_item, tail_flags, tile_successor_item, |
| * thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt>, |
| * that the @p tile_predecessor_item is @p 0, and that the |
| * @p tile_successor_item is @p 125. The corresponding output @p head_flags |
| * in those threads will be <tt>{ [0,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * and the corresponding output @p tail_flags in those threads will be |
| * <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,1] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning @p true |
| * if a discontinuity exists between @p a and @p b, otherwise @p false. @p b_index is the rank |
| * of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] tile_predecessor_item |
| * <b>[<em>thread</em><sub>0</sub> only]</b> Item with which to compare the first tile item |
| * (<tt>input<sub>0</sub></tt> from <em>thread</em><sub>0</sub>). |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeadsAndTails(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T tile_predecessor_item, |
| FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share first and last items |
| temp_storage.first_items[linear_tid] = input[0]; |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| T preds[ITEMS_PER_THREAD]; |
| |
| // Set flag for first thread-item |
| preds[0] = (linear_tid == 0) ? |
| tile_predecessor_item : // First thread |
| temp_storage.last_items[linear_tid - 1]; |
| |
| head_flags[0] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| preds[0], |
| input[0], |
| linear_tid * ITEMS_PER_THREAD); |
| |
| // Set flag for last thread-item |
| tail_flags[ITEMS_PER_THREAD - 1] = (linear_tid == BLOCK_THREADS - 1) ? |
| 1 : // Last thread |
| ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| temp_storage.first_items[linear_tid + 1], |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
| /** |
| * @brief Sets both head and tail flags indicating discontinuities between items partitioned |
| * across the thread block. |
| * |
| * @par |
| * - The flag <tt>head_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(</tt><em>previous-item</em><tt>, input<sub><em>i</em></sub>)</tt> |
| * returns @p true (where <em>previous-item</em> is either the preceding item |
| * in the same thread or the last item in the previous thread). |
| * - For <em>thread</em><sub>0</sub>, item <tt>input<sub>0</sub></tt> is compared |
| * against @p tile_predecessor_item. |
| * - The flag <tt>tail_flags<sub><em>i</em></sub></tt> is set for item |
| * <tt>input<sub><em>i</em></sub></tt> when |
| * <tt>flag_op(input<sub><em>i</em></sub>, </tt><em>next-item</em><tt>)</tt> |
| * returns @p true (where <em>next-item</em> is either the next item |
| * in the same thread or the first item in the next thread). |
| * - For <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>, item |
| * <tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> is compared |
| * against @p tile_successor_item. |
| * - @blocked |
| * - @granularity |
| * - @smemreuse |
| * |
| * @par Snippet |
| * The code snippet below illustrates the head- and tail-flagging of 512 integer items that |
| * are partitioned in a [<em>blocked arrangement</em>](index.html#sec5sec3) across 128 threads |
| * where each thread owns 4 consecutive items. |
| * @par |
| * @code |
| * #include <cub/cub.cuh> // or equivalently <cub/block/block_discontinuity.cuh> |
| * |
| * __global__ void ExampleKernel(...) |
| * { |
| * // Specialize BlockDiscontinuity for a 1D block of 128 threads of type int |
| * typedef cub::BlockDiscontinuity<int, 128> BlockDiscontinuity; |
| * |
| * // Allocate shared memory for BlockDiscontinuity |
| * __shared__ typename BlockDiscontinuity::TempStorage temp_storage; |
| * |
| * // Obtain a segment of consecutive items that are blocked across threads |
| * int thread_data[4]; |
| * ... |
| * |
| * // Have thread0 obtain the predecessor item for the entire tile |
| * int tile_predecessor_item; |
| * if (threadIdx.x == 0) tile_predecessor_item == ... |
| * |
| * // Have thread127 obtain the successor item for the entire tile |
| * int tile_successor_item; |
| * if (threadIdx.x == 127) tile_successor_item == ... |
| * |
| * // Collectively compute head and flags for discontinuities in the segment |
| * int head_flags[4]; |
| * int tail_flags[4]; |
| * BlockDiscontinuity(temp_storage).FlagTails( |
| * head_flags, tile_predecessor_item, tail_flags, tile_successor_item, |
| * thread_data, cub::Inequality()); |
| * |
| * @endcode |
| * @par |
| * Suppose the set of input @p thread_data across the block of threads is |
| * <tt>{ [0,0,1,1], [1,1,1,1], [2,3,3,3], ..., [124,125,125,125] }</tt>, |
| * that the @p tile_predecessor_item is @p 0, and that the |
| * @p tile_successor_item is @p 125. The corresponding output @p head_flags |
| * in those threads will be <tt>{ [0,0,1,0], [0,0,0,0], [1,1,0,0], [0,1,0,0], ... }</tt>. |
| * and the corresponding output @p tail_flags in those threads will be |
| * <tt>{ [0,1,0,0], [0,0,0,1], [1,0,0,...], ..., [1,0,0,0] }</tt>. |
| * |
| * @tparam ITEMS_PER_THREAD |
| * <b>[inferred]</b> The number of consecutive items partitioned onto each thread. |
| * |
| * @tparam FlagT |
| * <b>[inferred]</b> The flag type (must be an integer type) |
| * |
| * @tparam FlagOp |
| * <b>[inferred]</b> Binary predicate functor type having member |
| * <tt>T operator()(const T &a, const T &b)</tt> or member |
| * <tt>T operator()(const T &a, const T &b, unsigned int b_index)</tt>, and returning @p true |
| * if a discontinuity exists between @p a and @p b, otherwise @p false. @p b_index is the rank |
| * of b in the aggregate tile of data. |
| * |
| * @param[out] head_flags |
| * Calling thread's discontinuity head_flags |
| * |
| * @param[in] tile_predecessor_item |
| * <b>[<em>thread</em><sub>0</sub> only]</b> Item with which to compare the first tile item |
| * (<tt>input<sub>0</sub></tt> from <em>thread</em><sub>0</sub>). |
| * |
| * @param[out] tail_flags |
| * Calling thread's discontinuity tail_flags |
| * |
| * @param[in] tile_successor_item |
| * <b>[<em>thread</em><sub><tt>BLOCK_THREADS</tt>-1</sub> only]</b> Item with which to compare |
| * the last tile item (<tt>input</tt><sub><em>ITEMS_PER_THREAD</em>-1</sub> from |
| * <em>thread</em><sub><em>BLOCK_THREADS</em>-1</sub>). |
| * |
| * @param[in] input |
| * Calling thread's input items |
| * |
| * @param[in] flag_op |
| * Binary boolean flag predicate |
| */ |
| template <int ITEMS_PER_THREAD, typename FlagT, typename FlagOp> |
| __device__ __forceinline__ void FlagHeadsAndTails(FlagT (&head_flags)[ITEMS_PER_THREAD], |
| T tile_predecessor_item, |
| FlagT (&tail_flags)[ITEMS_PER_THREAD], |
| T tile_successor_item, |
| T (&input)[ITEMS_PER_THREAD], |
| FlagOp flag_op) |
| { |
| // Share first and last items |
| temp_storage.first_items[linear_tid] = input[0]; |
| temp_storage.last_items[linear_tid] = input[ITEMS_PER_THREAD - 1]; |
| |
| CTA_SYNC(); |
| |
| T preds[ITEMS_PER_THREAD]; |
| |
| // Set flag for first thread-item |
| preds[0] = (linear_tid == 0) ? |
| tile_predecessor_item : // First thread |
| temp_storage.last_items[linear_tid - 1]; |
| |
| head_flags[0] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| preds[0], |
| input[0], |
| linear_tid * ITEMS_PER_THREAD); |
| |
| // Set flag for last thread-item |
| T successor_item = (linear_tid == BLOCK_THREADS - 1) ? |
| tile_successor_item : // Last thread |
| temp_storage.first_items[linear_tid + 1]; |
| |
| tail_flags[ITEMS_PER_THREAD - 1] = ApplyOp<FlagOp>::FlagT( |
| flag_op, |
| input[ITEMS_PER_THREAD - 1], |
| successor_item, |
| (linear_tid * ITEMS_PER_THREAD) + ITEMS_PER_THREAD); |
| |
| // Set head_flags for remaining items |
| Iterate::FlagHeads(linear_tid, head_flags, input, preds, flag_op); |
| |
| // Set tail_flags for remaining items |
| Iterate::FlagTails(linear_tid, tail_flags, input, flag_op); |
| } |
| |
|
|
|
|
|
|
| //@} end member group |
| |
| }; |
|
|
|
|
| CUB_NAMESPACE_END |
|
|
