cub/block/block_run_length_decode.cuh
File members: cub/block/block_run_length_decode.cuh
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#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/block/block_scan.cuh>
#include <cub/thread/thread_search.cuh>
#include <cub/util_math.cuh>
#include <cub/util_namespace.cuh>
#include <cub/util_ptx.cuh>
#include <cub/util_type.cuh>
#include <limits>
#include <type_traits>
CUB_NAMESPACE_BEGIN
template <typename ItemT,
int BLOCK_DIM_X,
int RUNS_PER_THREAD,
int DECODED_ITEMS_PER_THREAD,
typename DecodedOffsetT = uint32_t,
int BLOCK_DIM_Y = 1,
int BLOCK_DIM_Z = 1>
class BlockRunLengthDecode
{
//---------------------------------------------------------------------
// CONFIGS & TYPE ALIASES
//---------------------------------------------------------------------
private:
static constexpr int BLOCK_THREADS = BLOCK_DIM_X * BLOCK_DIM_Y * BLOCK_DIM_Z;
static constexpr int BLOCK_RUNS = BLOCK_THREADS * RUNS_PER_THREAD;
using RunOffsetScanT = BlockScan<DecodedOffsetT, BLOCK_DIM_X, BLOCK_SCAN_RAKING_MEMOIZE, BLOCK_DIM_Y, BLOCK_DIM_Z>;
using RunOffsetT = uint32_t;
#ifndef DOXYGEN_SHOULD_SKIP_THIS // Do not document
union _TempStorage
{
typename RunOffsetScanT::TempStorage offset_scan;
struct
{
ItemT run_values[BLOCK_RUNS];
DecodedOffsetT run_offsets[BLOCK_RUNS];
} runs;
}; // union TempStorage
#endif // DOXYGEN_SHOULD_SKIP_THIS
_CCCL_DEVICE _CCCL_FORCEINLINE _TempStorage& PrivateStorage()
{
__shared__ _TempStorage private_storage;
return private_storage;
}
_TempStorage& temp_storage;
uint32_t linear_tid;
public:
struct TempStorage : Uninitialized<_TempStorage>
{};
//---------------------------------------------------------------------
// CONSTRUCTOR
//---------------------------------------------------------------------
template <typename RunLengthT, typename TotalDecodedSizeT>
_CCCL_DEVICE _CCCL_FORCEINLINE BlockRunLengthDecode(
TempStorage& temp_storage,
ItemT (&run_values)[RUNS_PER_THREAD],
RunLengthT (&run_lengths)[RUNS_PER_THREAD],
TotalDecodedSizeT& total_decoded_size)
: temp_storage(temp_storage.Alias())
, linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z))
{
InitWithRunLengths(run_values, run_lengths, total_decoded_size);
}
template <typename UserRunOffsetT>
_CCCL_DEVICE _CCCL_FORCEINLINE BlockRunLengthDecode(
TempStorage& temp_storage, ItemT (&run_values)[RUNS_PER_THREAD], UserRunOffsetT (&run_offsets)[RUNS_PER_THREAD])
: temp_storage(temp_storage.Alias())
, linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z))
{
InitWithRunOffsets(run_values, run_offsets);
}
template <typename RunLengthT, typename TotalDecodedSizeT>
_CCCL_DEVICE _CCCL_FORCEINLINE BlockRunLengthDecode(
ItemT (&run_values)[RUNS_PER_THREAD],
RunLengthT (&run_lengths)[RUNS_PER_THREAD],
TotalDecodedSizeT& total_decoded_size)
: temp_storage(PrivateStorage())
, linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z))
{
InitWithRunLengths(run_values, run_lengths, total_decoded_size);
}
template <typename UserRunOffsetT>
_CCCL_DEVICE _CCCL_FORCEINLINE
BlockRunLengthDecode(ItemT (&run_values)[RUNS_PER_THREAD], UserRunOffsetT (&run_offsets)[RUNS_PER_THREAD])
: temp_storage(PrivateStorage())
, linear_tid(RowMajorTid(BLOCK_DIM_X, BLOCK_DIM_Y, BLOCK_DIM_Z))
{
InitWithRunOffsets(run_values, run_offsets);
}
private:
template <int MAX_NUM_ITEMS, typename InputIteratorT, typename OffsetT, typename T>
_CCCL_DEVICE _CCCL_FORCEINLINE OffsetT StaticUpperBound(InputIteratorT input, OffsetT num_items, T val)
{
OffsetT lower_bound = 0;
OffsetT upper_bound = num_items;
#pragma unroll
for (int i = 0; i <= Log2<MAX_NUM_ITEMS>::VALUE; i++)
{
OffsetT mid = cub::MidPoint<OffsetT>(lower_bound, upper_bound);
mid = (cub::min)(mid, num_items - 1);
if (val < input[mid])
{
upper_bound = mid;
}
else
{
lower_bound = mid + 1;
}
}
return lower_bound;
}
template <typename RunOffsetT>
_CCCL_DEVICE _CCCL_FORCEINLINE void
InitWithRunOffsets(ItemT (&run_values)[RUNS_PER_THREAD], RunOffsetT (&run_offsets)[RUNS_PER_THREAD])
{
// Keep the runs' items and the offsets of each run's beginning in the temporary storage
RunOffsetT thread_dst_offset = static_cast<RunOffsetT>(linear_tid) * static_cast<RunOffsetT>(RUNS_PER_THREAD);
#pragma unroll
for (int i = 0; i < RUNS_PER_THREAD; i++)
{
temp_storage.runs.run_values[thread_dst_offset] = run_values[i];
temp_storage.runs.run_offsets[thread_dst_offset] = run_offsets[i];
thread_dst_offset++;
}
// Ensure run offsets and run values have been writen to shared memory
CTA_SYNC();
}
template <typename RunLengthT, typename TotalDecodedSizeT>
_CCCL_DEVICE _CCCL_FORCEINLINE void InitWithRunLengths(
ItemT (&run_values)[RUNS_PER_THREAD],
RunLengthT (&run_lengths)[RUNS_PER_THREAD],
TotalDecodedSizeT& total_decoded_size)
{
// Compute the offset for the beginning of each run
DecodedOffsetT run_offsets[RUNS_PER_THREAD];
#pragma unroll
for (int i = 0; i < RUNS_PER_THREAD; i++)
{
run_offsets[i] = static_cast<DecodedOffsetT>(run_lengths[i]);
}
DecodedOffsetT decoded_size_aggregate;
RunOffsetScanT(this->temp_storage.offset_scan).ExclusiveSum(run_offsets, run_offsets, decoded_size_aggregate);
total_decoded_size = static_cast<TotalDecodedSizeT>(decoded_size_aggregate);
// Ensure the prefix scan's temporary storage can be reused (may be superfluous, but depends on scan implementation)
CTA_SYNC();
InitWithRunOffsets(run_values, run_offsets);
}
public:
template <typename RelativeOffsetT>
_CCCL_DEVICE _CCCL_FORCEINLINE void RunLengthDecode(
ItemT (&decoded_items)[DECODED_ITEMS_PER_THREAD],
RelativeOffsetT (&item_offsets)[DECODED_ITEMS_PER_THREAD],
DecodedOffsetT from_decoded_offset = 0)
{
// The (global) offset of the first item decoded by this thread
DecodedOffsetT thread_decoded_offset = from_decoded_offset + linear_tid * DECODED_ITEMS_PER_THREAD;
// The run that the first decoded item of this thread belongs to
// If this thread's <thread_decoded_offset> is already beyond the total decoded size, it will be assigned to the
// last run
RunOffsetT assigned_run =
StaticUpperBound<BLOCK_RUNS>(temp_storage.runs.run_offsets, BLOCK_RUNS, thread_decoded_offset)
- static_cast<RunOffsetT>(1U);
DecodedOffsetT assigned_run_begin = temp_storage.runs.run_offsets[assigned_run];
// If this thread is getting assigned the last run, we make sure it will not fetch any other run after this
DecodedOffsetT assigned_run_end =
(assigned_run == BLOCK_RUNS - 1)
? thread_decoded_offset + DECODED_ITEMS_PER_THREAD
: temp_storage.runs.run_offsets[assigned_run + 1];
ItemT val = temp_storage.runs.run_values[assigned_run];
#pragma unroll
for (DecodedOffsetT i = 0; i < DECODED_ITEMS_PER_THREAD; i++)
{
decoded_items[i] = val;
item_offsets[i] = thread_decoded_offset - assigned_run_begin;
// A thread only needs to fetch the next run if this was not the last loop iteration
const bool is_final_loop_iteration = (i + 1 >= DECODED_ITEMS_PER_THREAD);
if (!is_final_loop_iteration && (thread_decoded_offset == assigned_run_end - 1))
{
// We make sure that a thread is not re-entering this conditional when being assigned to the last run already by
// extending the last run's length to all the thread's item
assigned_run++;
assigned_run_begin = temp_storage.runs.run_offsets[assigned_run];
// If this thread is getting assigned the last run, we make sure it will not fetch any other run after this
assigned_run_end = (assigned_run == BLOCK_RUNS - 1)
? thread_decoded_offset + DECODED_ITEMS_PER_THREAD
: temp_storage.runs.run_offsets[assigned_run + 1];
val = temp_storage.runs.run_values[assigned_run];
}
thread_decoded_offset++;
}
}
_CCCL_DEVICE _CCCL_FORCEINLINE void
RunLengthDecode(ItemT (&decoded_items)[DECODED_ITEMS_PER_THREAD], DecodedOffsetT from_decoded_offset = 0)
{
DecodedOffsetT item_offsets[DECODED_ITEMS_PER_THREAD];
RunLengthDecode(decoded_items, item_offsets, from_decoded_offset);
}
};
CUB_NAMESPACE_END