cub::ShuffleIndex#

template<int LOGICAL_WARP_THREADS, typename T>
T cub::ShuffleIndex(
T input,
int src_lane,
unsigned int member_mask,
)#

Shuffle-broadcast for any data type.

Each warp-lane obtains the value input contributed by warp-lane. For src_lane < 0 or src_lane >= WARP_THREADS, then the thread’s own input is returned to the thread. ../../_images/shfl_broadcast_logo.png

  • Available only for SM3.0 or newer

Snippet

The code snippet below illustrates each thread obtaining a double value from warp-lane0.

#include <cub/cub.cuh>   // or equivalently <cub/util_ptx.cuh>

__global__ void ExampleKernel(...)
{
    // Obtain one input item per thread
    double thread_data = ...

    // Obtain item from thread 0
    double peer_data = ShuffleIndex<32>(thread_data, 0, 0xffffffff);

Suppose the set of input thread_data across the first warp of threads is {1.0, 2.0, 3.0, 4.0, 5.0, ..., 32.0}. The corresponding output peer_data will be {1.0, 1.0, 1.0, 1.0, 1.0, ..., 1.0}.

Template Parameters:

  • LOGICAL_WARP_THREADS – The number of threads per “logical” warp. Must be a power-of-two <= 32.

  • T – [inferred] The input/output element type

Parameters:

  • input – [in] The value to broadcast

  • src_lane – [in] Which warp lane is to do the broadcasting

  • member_mask – [in] 32-bit mask of participating warp lanes

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