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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::WarpScanShfl provides SHFL-based variants of parallel prefix scan of items partitioned across a CUDA thread warp.
*/
#pragma once
#include "../../config.cuh"
#include "../../thread/thread_operators.cuh"
#include "../../util_type.cuh"
#include "../../util_ptx.cuh"
/// Optional outer namespace(s)
CUB_NS_PREFIX
/// CUB namespace
namespace cub {
/**
* \brief WarpScanShfl provides SHFL-based variants of parallel prefix scan of items partitioned across a CUDA thread warp.
*
* LOGICAL_WARP_THREADS must be a power-of-two
*/
template <
typename T, ///< Data type being scanned
int LOGICAL_WARP_THREADS, ///< Number of threads per logical warp
int PTX_ARCH> ///< The PTX compute capability for which to to specialize this collective
struct WarpScanShfl
{
//---------------------------------------------------------------------
// Constants and type definitions
//---------------------------------------------------------------------
enum
{
/// Whether the logical warp size and the PTX warp size coincide
IS_ARCH_WARP = (LOGICAL_WARP_THREADS == CUB_WARP_THREADS(PTX_ARCH)),
/// The number of warp scan steps
STEPS = Log2<LOGICAL_WARP_THREADS>::VALUE,
/// The 5-bit SHFL mask for logically splitting warps into sub-segments starts 8-bits up
SHFL_C = (CUB_WARP_THREADS(PTX_ARCH) - LOGICAL_WARP_THREADS) << 8
};
template <typename S>
struct IntegerTraits
{
enum {
///Whether the data type is a small (32b or less) integer for which we can use a single SFHL instruction per exchange
IS_SMALL_UNSIGNED = (Traits<S>::CATEGORY == UNSIGNED_INTEGER) && (sizeof(S) <= sizeof(unsigned int))
};
};
/// Shared memory storage layout type
struct TempStorage {};
//---------------------------------------------------------------------
// Thread fields
//---------------------------------------------------------------------
/// Lane index in logical warp
unsigned int lane_id;
/// Logical warp index in 32-thread physical warp
unsigned int warp_id;
/// 32-thread physical warp member mask of logical warp
unsigned int member_mask;
//---------------------------------------------------------------------
// Construction
//---------------------------------------------------------------------
/// Constructor
__device__ __forceinline__ WarpScanShfl(
TempStorage &/*temp_storage*/)
{
lane_id = LaneId();
warp_id = 0;
member_mask = 0xffffffffu >> (CUB_WARP_THREADS(PTX_ARCH) - LOGICAL_WARP_THREADS);
if (!IS_ARCH_WARP)
{
warp_id = lane_id / LOGICAL_WARP_THREADS;
lane_id = lane_id % LOGICAL_WARP_THREADS;
member_mask = member_mask << (warp_id * LOGICAL_WARP_THREADS);
}
}
//---------------------------------------------------------------------
// Inclusive scan steps
//---------------------------------------------------------------------
/// Inclusive prefix scan step (specialized for summation across int32 types)
__device__ __forceinline__ int InclusiveScanStep(
int input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
int output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .s32 r0;"
" .reg .pred p;"
" shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
" @p add.s32 r0, r0, %4;"
" mov.s32 %0, r0;"
"}"
: "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .s32 r0;"
" .reg .pred p;"
" shfl.up.b32 r0|p, %1, %2, %3;"
" @p add.s32 r0, r0, %4;"
" mov.s32 %0, r0;"
"}"
: "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input));
#endif
return output;
}
/// Inclusive prefix scan step (specialized for summation across uint32 types)
__device__ __forceinline__ unsigned int InclusiveScanStep(
unsigned int input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
unsigned int output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .u32 r0;"
" .reg .pred p;"
" shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
" @p add.u32 r0, r0, %4;"
" mov.u32 %0, r0;"
"}"
: "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .u32 r0;"
" .reg .pred p;"
" shfl.up.b32 r0|p, %1, %2, %3;"
" @p add.u32 r0, r0, %4;"
" mov.u32 %0, r0;"
"}"
: "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input));
#endif
return output;
}
/// Inclusive prefix scan step (specialized for summation across fp32 types)
__device__ __forceinline__ float InclusiveScanStep(
float input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
float output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .f32 r0;"
" .reg .pred p;"
" shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
" @p add.f32 r0, r0, %4;"
" mov.f32 %0, r0;"
"}"
: "=f"(output) : "f"(input), "r"(offset), "r"(shfl_c), "f"(input), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .f32 r0;"
" .reg .pred p;"
" shfl.up.b32 r0|p, %1, %2, %3;"
" @p add.f32 r0, r0, %4;"
" mov.f32 %0, r0;"
"}"
: "=f"(output) : "f"(input), "r"(offset), "r"(shfl_c), "f"(input));
#endif
return output;
}
/// Inclusive prefix scan step (specialized for summation across unsigned long long types)
__device__ __forceinline__ unsigned long long InclusiveScanStep(
unsigned long long input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
unsigned long long output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .u64 r0;"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" mov.b64 {lo, hi}, %1;"
" shfl.sync.up.b32 lo|p, lo, %2, %3, %5;"
" shfl.sync.up.b32 hi|p, hi, %2, %3, %5;"
" mov.b64 r0, {lo, hi};"
" @p add.u64 r0, r0, %4;"
" mov.u64 %0, r0;"
"}"
: "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .u64 r0;"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" mov.b64 {lo, hi}, %1;"
" shfl.up.b32 lo|p, lo, %2, %3;"
" shfl.up.b32 hi|p, hi, %2, %3;"
" mov.b64 r0, {lo, hi};"
" @p add.u64 r0, r0, %4;"
" mov.u64 %0, r0;"
"}"
: "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input));
#endif
return output;
}
/// Inclusive prefix scan step (specialized for summation across long long types)
__device__ __forceinline__ long long InclusiveScanStep(
long long input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
long long output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .s64 r0;"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" mov.b64 {lo, hi}, %1;"
" shfl.sync.up.b32 lo|p, lo, %2, %3, %5;"
" shfl.sync.up.b32 hi|p, hi, %2, %3, %5;"
" mov.b64 r0, {lo, hi};"
" @p add.s64 r0, r0, %4;"
" mov.s64 %0, r0;"
"}"
: "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .s64 r0;"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" mov.b64 {lo, hi}, %1;"
" shfl.up.b32 lo|p, lo, %2, %3;"
" shfl.up.b32 hi|p, hi, %2, %3;"
" mov.b64 r0, {lo, hi};"
" @p add.s64 r0, r0, %4;"
" mov.s64 %0, r0;"
"}"
: "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input));
#endif
return output;
}
/// Inclusive prefix scan step (specialized for summation across fp64 types)
__device__ __forceinline__ double InclusiveScanStep(
double input, ///< [in] Calling thread's input item.
cub::Sum /*scan_op*/, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
double output;
int shfl_c = first_lane | SHFL_C; // Shuffle control (mask and first-lane)
// Use predicate set from SHFL to guard against invalid peers
#ifdef CUB_USE_COOPERATIVE_GROUPS
asm volatile(
"{"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" .reg .f64 r0;"
" mov.b64 %0, %1;"
" mov.b64 {lo, hi}, %1;"
" shfl.sync.up.b32 lo|p, lo, %2, %3, %4;"
" shfl.sync.up.b32 hi|p, hi, %2, %3, %4;"
" mov.b64 r0, {lo, hi};"
" @p add.f64 %0, %0, r0;"
"}"
: "=d"(output) : "d"(input), "r"(offset), "r"(shfl_c), "r"(member_mask));
#else
asm volatile(
"{"
" .reg .u32 lo;"
" .reg .u32 hi;"
" .reg .pred p;"
" .reg .f64 r0;"
" mov.b64 %0, %1;"
" mov.b64 {lo, hi}, %1;"
" shfl.up.b32 lo|p, lo, %2, %3;"
" shfl.up.b32 hi|p, hi, %2, %3;"
" mov.b64 r0, {lo, hi};"
" @p add.f64 %0, %0, r0;"
"}"
: "=d"(output) : "d"(input), "r"(offset), "r"(shfl_c));
#endif
return output;
}
/*
/// Inclusive prefix scan (specialized for ReduceBySegmentOp<cub::Sum> across KeyValuePair<OffsetT, Value> types)
template <typename Value, typename OffsetT>
__device__ __forceinline__ KeyValuePair<OffsetT, Value>InclusiveScanStep(
KeyValuePair<OffsetT, Value> input, ///< [in] Calling thread's input item.
ReduceBySegmentOp<cub::Sum> scan_op, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
KeyValuePair<OffsetT, Value> output;
output.value = InclusiveScanStep(input.value, cub::Sum(), first_lane, offset, Int2Type<IntegerTraits<Value>::IS_SMALL_UNSIGNED>());
output.key = InclusiveScanStep(input.key, cub::Sum(), first_lane, offset, Int2Type<IntegerTraits<OffsetT>::IS_SMALL_UNSIGNED>());
if (input.key > 0)
output.value = input.value;
return output;
}
*/
/// Inclusive prefix scan step (generic)
template <typename _T, typename ScanOpT>
__device__ __forceinline__ _T InclusiveScanStep(
_T input, ///< [in] Calling thread's input item.
ScanOpT scan_op, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset) ///< [in] Up-offset to pull from
{
_T temp = ShuffleUp<LOGICAL_WARP_THREADS>(input, offset, first_lane, member_mask);
// Perform scan op if from a valid peer
_T output = scan_op(temp, input);
if (static_cast<int>(lane_id) < first_lane + offset)
output = input;
return output;
}
/// Inclusive prefix scan step (specialized for small integers size 32b or less)
template <typename _T, typename ScanOpT>
__device__ __forceinline__ _T InclusiveScanStep(
_T input, ///< [in] Calling thread's input item.
ScanOpT scan_op, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset, ///< [in] Up-offset to pull from
Int2Type<true> /*is_small_unsigned*/) ///< [in] Marker type indicating whether T is a small integer
{
return InclusiveScanStep(input, scan_op, first_lane, offset);
}
/// Inclusive prefix scan step (specialized for types other than small integers size 32b or less)
template <typename _T, typename ScanOpT>
__device__ __forceinline__ _T InclusiveScanStep(
_T input, ///< [in] Calling thread's input item.
ScanOpT scan_op, ///< [in] Binary scan operator
int first_lane, ///< [in] Index of first lane in segment
int offset, ///< [in] Up-offset to pull from
Int2Type<false> /*is_small_unsigned*/) ///< [in] Marker type indicating whether T is a small integer
{
return InclusiveScanStep(input, scan_op, first_lane, offset);
}
/******************************************************************************
* Interface
******************************************************************************/
//---------------------------------------------------------------------
// Broadcast
//---------------------------------------------------------------------
/// Broadcast
__device__ __forceinline__ T Broadcast(
T input, ///< [in] The value to broadcast
int src_lane) ///< [in] Which warp lane is to do the broadcasting
{
return ShuffleIndex<LOGICAL_WARP_THREADS>(input, src_lane, member_mask);
}
//---------------------------------------------------------------------
// Inclusive operations
//---------------------------------------------------------------------
/// Inclusive scan
template <typename _T, typename ScanOpT>
__device__ __forceinline__ void InclusiveScan(
_T input, ///< [in] Calling thread's input item.
_T &inclusive_output, ///< [out] Calling thread's output item. May be aliased with \p input.
ScanOpT scan_op) ///< [in] Binary scan operator
{
inclusive_output = input;
// Iterate scan steps
int segment_first_lane = 0;
// Iterate scan steps
#pragma unroll
for (int STEP = 0; STEP < STEPS; STEP++)
{
inclusive_output = InclusiveScanStep(
inclusive_output,
scan_op,
segment_first_lane,
(1 << STEP),
Int2Type<IntegerTraits<T>::IS_SMALL_UNSIGNED>());
}
}
/// Inclusive scan, specialized for reduce-value-by-key
template <typename KeyT, typename ValueT, typename ReductionOpT>
__device__ __forceinline__ void InclusiveScan(
KeyValuePair<KeyT, ValueT> input, ///< [in] Calling thread's input item.
KeyValuePair<KeyT, ValueT> &inclusive_output, ///< [out] Calling thread's output item. May be aliased with \p input.
ReduceByKeyOp<ReductionOpT > scan_op) ///< [in] Binary scan operator
{
inclusive_output = input;
KeyT pred_key = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive_output.key, 1, 0, member_mask);
unsigned int ballot = WARP_BALLOT((pred_key != inclusive_output.key), member_mask);
// Mask away all lanes greater than ours
ballot = ballot & LaneMaskLe();
// Find index of first set bit
int segment_first_lane = CUB_MAX(0, 31 - __clz(ballot));
// Iterate scan steps
#pragma unroll
for (int STEP = 0; STEP < STEPS; STEP++)
{
inclusive_output.value = InclusiveScanStep(
inclusive_output.value,
scan_op.op,
segment_first_lane,
(1 << STEP),
Int2Type<IntegerTraits<T>::IS_SMALL_UNSIGNED>());
}
}
/// Inclusive scan with aggregate
template <typename ScanOpT>
__device__ __forceinline__ void InclusiveScan(
T input, ///< [in] Calling thread's input item.
T &inclusive_output, ///< [out] Calling thread's output item. May be aliased with \p input.
ScanOpT scan_op, ///< [in] Binary scan operator
T &warp_aggregate) ///< [out] Warp-wide aggregate reduction of input items.
{
InclusiveScan(input, inclusive_output, scan_op);
// Grab aggregate from last warp lane
warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive_output, LOGICAL_WARP_THREADS - 1, member_mask);
}
//---------------------------------------------------------------------
// Get exclusive from inclusive
//---------------------------------------------------------------------
/// Update inclusive and exclusive using input and inclusive
template <typename ScanOpT, typename IsIntegerT>
__device__ __forceinline__ void Update(
T /*input*/, ///< [in]
T &inclusive, ///< [in, out]
T &exclusive, ///< [out]
ScanOpT /*scan_op*/, ///< [in]
IsIntegerT /*is_integer*/) ///< [in]
{
// initial value unknown
exclusive = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive, 1, 0, member_mask);
}
/// Update inclusive and exclusive using input and inclusive (specialized for summation of integer types)
__device__ __forceinline__ void Update(
T input,
T &inclusive,
T &exclusive,
cub::Sum /*scan_op*/,
Int2Type<true> /*is_integer*/)
{
// initial value presumed 0
exclusive = inclusive - input;
}
/// Update inclusive and exclusive using initial value using input, inclusive, and initial value
template <typename ScanOpT, typename IsIntegerT>
__device__ __forceinline__ void Update (
T /*input*/,
T &inclusive,
T &exclusive,
ScanOpT scan_op,
T initial_value,
IsIntegerT /*is_integer*/)
{
inclusive = scan_op(initial_value, inclusive);
exclusive = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive, 1, 0, member_mask);
if (lane_id == 0)
exclusive = initial_value;
}
/// Update inclusive and exclusive using initial value using input and inclusive (specialized for summation of integer types)
__device__ __forceinline__ void Update (
T input,
T &inclusive,
T &exclusive,
cub::Sum scan_op,
T initial_value,
Int2Type<true> /*is_integer*/)
{
inclusive = scan_op(initial_value, inclusive);
exclusive = inclusive - input;
}
/// Update inclusive, exclusive, and warp aggregate using input and inclusive
template <typename ScanOpT, typename IsIntegerT>
__device__ __forceinline__ void Update (
T input,
T &inclusive,
T &exclusive,
T &warp_aggregate,
ScanOpT scan_op,
IsIntegerT is_integer)
{
warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive, LOGICAL_WARP_THREADS - 1, member_mask);
Update(input, inclusive, exclusive, scan_op, is_integer);
}
/// Update inclusive, exclusive, and warp aggregate using input, inclusive, and initial value
template <typename ScanOpT, typename IsIntegerT>
__device__ __forceinline__ void Update (
T input,
T &inclusive,
T &exclusive,
T &warp_aggregate,
ScanOpT scan_op,
T initial_value,
IsIntegerT is_integer)
{
warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive, LOGICAL_WARP_THREADS - 1, member_mask);
Update(input, inclusive, exclusive, scan_op, initial_value, is_integer);
}
};
} // CUB namespace
CUB_NS_POSTFIX // Optional outer namespace(s)