
/******************************************************************************
 * 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::DeviceSpmv provides device-wide parallel operations for performing sparse-matrix * vector multiplication (SpMV).
 */

#pragma once

#include <stdio.h>
#include <iterator>

#include "../../agent/single_pass_scan_operators.cuh"
#include "../../agent/agent_segment_fixup.cuh"
#include "../../agent/agent_spmv_orig.cuh"
#include "../../util_type.cuh"
#include "../../util_debug.cuh"
#include "../../util_device.cuh"
#include "../../util_math.cuh"
#include "../../thread/thread_search.cuh"
#include "../../grid/grid_queue.cuh"
#include "../../config.cuh"

#include <thrust/system/cuda/detail/core/triple_chevron_launch.h>

CUB_NAMESPACE_BEGIN


/******************************************************************************
 * SpMV kernel entry points
 *****************************************************************************/

/**
 * Spmv search kernel. Identifies merge path starting coordinates for each tile.
 */
template <
    typename    AgentSpmvPolicyT,           ///< Parameterized SpmvPolicy tuning policy type
    typename    ValueT,                     ///< Matrix and vector value type
    typename    OffsetT>                    ///< Signed integer type for sequence offsets
__global__ void DeviceSpmv1ColKernel(
    SpmvParams<ValueT, OffsetT> spmv_params)                ///< [in] SpMV input parameter bundle
{
    typedef CacheModifiedInputIterator<
            AgentSpmvPolicyT::VECTOR_VALUES_LOAD_MODIFIER,
            ValueT,
            OffsetT>
        VectorValueIteratorT;

    VectorValueIteratorT wrapped_vector_x(spmv_params.d_vector_x);

    int row_idx = (blockIdx.x * blockDim.x) + threadIdx.x;
    if (row_idx < spmv_params.num_rows)
    {
        OffsetT     end_nonzero_idx = spmv_params.d_row_end_offsets[row_idx];
        OffsetT     nonzero_idx = spmv_params.d_row_end_offsets[row_idx - 1];

        ValueT value = 0.0;
        if (end_nonzero_idx != nonzero_idx)
        {
            value = spmv_params.d_values[nonzero_idx] * wrapped_vector_x[spmv_params.d_column_indices[nonzero_idx]];
        }

        spmv_params.d_vector_y[row_idx] = value;
    }
}


/**
 * Spmv search kernel. Identifies merge path starting coordinates for each tile.
 */
template <
    typename    SpmvPolicyT,                    ///< Parameterized SpmvPolicy tuning policy type
    typename    OffsetT,                        ///< Signed integer type for sequence offsets
    typename    CoordinateT,                    ///< Merge path coordinate type
    typename    SpmvParamsT>                    ///< SpmvParams type
__global__ void DeviceSpmvSearchKernel(
    int             num_merge_tiles,            ///< [in] Number of SpMV merge tiles (spmv grid size)
    CoordinateT*    d_tile_coordinates,         ///< [out] Pointer to the temporary array of tile starting coordinates
    SpmvParamsT     spmv_params)                ///< [in] SpMV input parameter bundle
{
    /// Constants
    enum
    {
        BLOCK_THREADS           = SpmvPolicyT::BLOCK_THREADS,
        ITEMS_PER_THREAD        = SpmvPolicyT::ITEMS_PER_THREAD,
        TILE_ITEMS              = BLOCK_THREADS * ITEMS_PER_THREAD,
    };

    typedef CacheModifiedInputIterator<
            SpmvPolicyT::ROW_OFFSETS_SEARCH_LOAD_MODIFIER,
            OffsetT,
            OffsetT>
        RowOffsetsSearchIteratorT;

    // Find the starting coordinate for all tiles (plus the end coordinate of the last one)
    int tile_idx = (blockIdx.x * blockDim.x) + threadIdx.x;
    if (tile_idx < num_merge_tiles + 1)
    {
        OffsetT                         diagonal = (tile_idx * TILE_ITEMS);
        CoordinateT                     tile_coordinate;
        CountingInputIterator<OffsetT>  nonzero_indices(0);

        // Search the merge path
        MergePathSearch(
            diagonal,
            RowOffsetsSearchIteratorT(spmv_params.d_row_end_offsets),
            nonzero_indices,
            spmv_params.num_rows,
            spmv_params.num_nonzeros,
            tile_coordinate);

        // Output starting offset
        d_tile_coordinates[tile_idx] = tile_coordinate;
    }
}


/**
 * Spmv agent entry point
 */
template <
    typename        SpmvPolicyT,                ///< Parameterized SpmvPolicy tuning policy type
    typename        ScanTileStateT,             ///< Tile status interface type
    typename        ValueT,                     ///< Matrix and vector value type
    typename        OffsetT,                    ///< Signed integer type for sequence offsets
    typename        CoordinateT,                ///< Merge path coordinate type
    bool            HAS_ALPHA,                  ///< Whether the input parameter Alpha is 1
    bool            HAS_BETA>                   ///< Whether the input parameter Beta is 0
__launch_bounds__ (int(SpmvPolicyT::BLOCK_THREADS))
__global__ void DeviceSpmvKernel(
    SpmvParams<ValueT, OffsetT>     spmv_params,                ///< [in] SpMV input parameter bundle
    CoordinateT*                    d_tile_coordinates,         ///< [in] Pointer to the temporary array of tile starting coordinates
    KeyValuePair<OffsetT,ValueT>*   d_tile_carry_pairs,         ///< [out] Pointer to the temporary array carry-out dot product row-ids, one per block
    int                             num_tiles,                  ///< [in] Number of merge tiles
    ScanTileStateT                  tile_state,                 ///< [in] Tile status interface for fixup reduce-by-key kernel
    int                             num_segment_fixup_tiles)    ///< [in] Number of reduce-by-key tiles (fixup grid size)
{
    // Spmv agent type specialization
    typedef AgentSpmv<
            SpmvPolicyT,
            ValueT,
            OffsetT,
            HAS_ALPHA,
            HAS_BETA>
        AgentSpmvT;

    // Shared memory for AgentSpmv
    __shared__ typename AgentSpmvT::TempStorage temp_storage;

    AgentSpmvT(temp_storage, spmv_params).ConsumeTile(
        d_tile_coordinates,
        d_tile_carry_pairs,
        num_tiles);

    // Initialize fixup tile status
    tile_state.InitializeStatus(num_segment_fixup_tiles);

}


/**
 * Multi-block reduce-by-key sweep kernel entry point
 */
template <
    typename    AgentSegmentFixupPolicyT,       ///< Parameterized AgentSegmentFixupPolicy tuning policy type
    typename    PairsInputIteratorT,            ///< Random-access input iterator type for keys
    typename    AggregatesOutputIteratorT,      ///< Random-access output iterator type for values
    typename    OffsetT,                        ///< Signed integer type for global offsets
    typename    ScanTileStateT>                 ///< Tile status interface type
__launch_bounds__ (int(AgentSegmentFixupPolicyT::BLOCK_THREADS))
__global__ void DeviceSegmentFixupKernel(
    PairsInputIteratorT         d_pairs_in,         ///< [in] Pointer to the array carry-out dot product row-ids, one per spmv block
    AggregatesOutputIteratorT   d_aggregates_out,   ///< [in,out] Output value aggregates
    OffsetT                     num_items,          ///< [in] Total number of items to select from
    int                         num_tiles,          ///< [in] Total number of tiles for the entire problem
    ScanTileStateT              tile_state)         ///< [in] Tile status interface
{
    // Thread block type for reducing tiles of value segments
    typedef AgentSegmentFixup<
            AgentSegmentFixupPolicyT,
            PairsInputIteratorT,
            AggregatesOutputIteratorT,
            cub::Equality,
            cub::Sum,
            OffsetT>
        AgentSegmentFixupT;

    // Shared memory for AgentSegmentFixup
    __shared__ typename AgentSegmentFixupT::TempStorage temp_storage;

    // Process tiles
    AgentSegmentFixupT(temp_storage, d_pairs_in, d_aggregates_out, cub::Equality(), cub::Sum()).ConsumeRange(
        num_items,
        num_tiles,
        tile_state);
}


/******************************************************************************
 * Dispatch
 ******************************************************************************/

/**
 * Utility class for dispatching the appropriately-tuned kernels for DeviceSpmv
 */
template <
    typename    ValueT,                     ///< Matrix and vector value type
    typename    OffsetT>                    ///< Signed integer type for global offsets
struct DispatchSpmv
{
    //---------------------------------------------------------------------
    // Constants and Types
    //---------------------------------------------------------------------

    enum
    {
        INIT_KERNEL_THREADS = 128
    };

    // SpmvParams bundle type
    typedef SpmvParams<ValueT, OffsetT> SpmvParamsT;

    // 2D merge path coordinate type
    typedef typename CubVector<OffsetT, 2>::Type CoordinateT;

    // Tile status descriptor interface type
    typedef ReduceByKeyScanTileState<ValueT, OffsetT> ScanTileStateT;

    // Tuple type for scanning (pairs accumulated segment-value with segment-index)
    typedef KeyValuePair<OffsetT, ValueT> KeyValuePairT;


    //---------------------------------------------------------------------
    // Tuning policies
    //---------------------------------------------------------------------

    /// SM35
    struct Policy350
    {
        typedef AgentSpmvPolicy<
                (sizeof(ValueT) > 4) ? 96 : 128,
                (sizeof(ValueT) > 4) ? 4 : 7,
                LOAD_LDG,
                LOAD_CA,
                LOAD_LDG,
                LOAD_LDG,
                LOAD_LDG,
                (sizeof(ValueT) > 4) ? true : false,
                BLOCK_SCAN_WARP_SCANS>
            SpmvPolicyT;

        typedef AgentSegmentFixupPolicy<
                128,
                3,
                BLOCK_LOAD_VECTORIZE,
                LOAD_LDG,
                BLOCK_SCAN_WARP_SCANS>
            SegmentFixupPolicyT;
    };


    /// SM37
    struct Policy370
    {

        typedef AgentSpmvPolicy<
                (sizeof(ValueT) > 4) ? 128 : 128,
                (sizeof(ValueT) > 4) ? 9 : 14,
                LOAD_LDG,
                LOAD_CA,
                LOAD_LDG,
                LOAD_LDG,
                LOAD_LDG,
                false,
                BLOCK_SCAN_WARP_SCANS>
            SpmvPolicyT;

        typedef AgentSegmentFixupPolicy<
                128,
                3,
                BLOCK_LOAD_VECTORIZE,
                LOAD_LDG,
                BLOCK_SCAN_WARP_SCANS>
            SegmentFixupPolicyT;
    };

    /// SM50
    struct Policy500
    {
        typedef AgentSpmvPolicy<
                (sizeof(ValueT) > 4) ? 64 : 128,
                (sizeof(ValueT) > 4) ? 6 : 7,
                LOAD_LDG,
                LOAD_DEFAULT,
                (sizeof(ValueT) > 4) ? LOAD_LDG : LOAD_DEFAULT,
                (sizeof(ValueT) > 4) ? LOAD_LDG : LOAD_DEFAULT,
                LOAD_LDG,
                (sizeof(ValueT) > 4) ? true : false,
                (sizeof(ValueT) > 4) ? BLOCK_SCAN_WARP_SCANS : BLOCK_SCAN_RAKING_MEMOIZE>
            SpmvPolicyT;


        typedef AgentSegmentFixupPolicy<
                128,
                3,
                BLOCK_LOAD_VECTORIZE,
                LOAD_LDG,
                BLOCK_SCAN_RAKING_MEMOIZE>
            SegmentFixupPolicyT;
    };


    /// SM60
    struct Policy600
    {
        typedef AgentSpmvPolicy<
                (sizeof(ValueT) > 4) ? 64 : 128,
                (sizeof(ValueT) > 4) ? 5 : 7,
                LOAD_DEFAULT,
                LOAD_DEFAULT,
                LOAD_DEFAULT,
                LOAD_DEFAULT,
                LOAD_DEFAULT,
                false,
                BLOCK_SCAN_WARP_SCANS>
            SpmvPolicyT;


        typedef AgentSegmentFixupPolicy<
                128,
                3,
                BLOCK_LOAD_DIRECT,
                LOAD_LDG,
                BLOCK_SCAN_WARP_SCANS>
            SegmentFixupPolicyT;
    };



    //---------------------------------------------------------------------
    // Tuning policies of current PTX compiler pass
    //---------------------------------------------------------------------

#if (CUB_PTX_ARCH >= 600)
    typedef Policy600 PtxPolicy;

#elif (CUB_PTX_ARCH >= 500)
    typedef Policy500 PtxPolicy;

#elif (CUB_PTX_ARCH >= 370)
    typedef Policy370 PtxPolicy;

#else
    typedef Policy350 PtxPolicy;

#endif

    // "Opaque" policies (whose parameterizations aren't reflected in the type signature)
    struct PtxSpmvPolicyT : PtxPolicy::SpmvPolicyT {};
    struct PtxSegmentFixupPolicy : PtxPolicy::SegmentFixupPolicyT {};


    //---------------------------------------------------------------------
    // Utilities
    //---------------------------------------------------------------------

    /**
     * Initialize kernel dispatch configurations with the policies corresponding to the PTX assembly we will use
     */
    template <typename KernelConfig>
    CUB_RUNTIME_FUNCTION __forceinline__
    static void InitConfigs(
        int             ptx_version,
        KernelConfig    &spmv_config,
        KernelConfig    &segment_fixup_config)
    {
        if (CUB_IS_DEVICE_CODE)
        {
            #if CUB_INCLUDE_DEVICE_CODE
                // We're on the device, so initialize the kernel dispatch configurations with the current PTX policy
                spmv_config.template Init<PtxSpmvPolicyT>();
                segment_fixup_config.template Init<PtxSegmentFixupPolicy>();
            #endif
        }
        else
        {
            #if CUB_INCLUDE_HOST_CODE
                // We're on the host, so lookup and initialize the kernel dispatch configurations with the policies that match the device's PTX version
                if (ptx_version >= 600)
                {
                    spmv_config.template            Init<typename Policy600::SpmvPolicyT>();
                    segment_fixup_config.template   Init<typename Policy600::SegmentFixupPolicyT>();
                }
                else if (ptx_version >= 500)
                {
                    spmv_config.template            Init<typename Policy500::SpmvPolicyT>();
                    segment_fixup_config.template   Init<typename Policy500::SegmentFixupPolicyT>();
                }
                else if (ptx_version >= 370)
                {
                    spmv_config.template            Init<typename Policy370::SpmvPolicyT>();
                    segment_fixup_config.template   Init<typename Policy370::SegmentFixupPolicyT>();
                }
                else
                {
                    spmv_config.template            Init<typename Policy350::SpmvPolicyT>();
                    segment_fixup_config.template   Init<typename Policy350::SegmentFixupPolicyT>();
                }
            #endif
        }
    }


    /**
     * Kernel kernel dispatch configuration.
     */
    struct KernelConfig
    {
        int block_threads;
        int items_per_thread;
        int tile_items;

        template <typename PolicyT>
        CUB_RUNTIME_FUNCTION __forceinline__
        void Init()
        {
            block_threads       = PolicyT::BLOCK_THREADS;
            items_per_thread    = PolicyT::ITEMS_PER_THREAD;
            tile_items          = block_threads * items_per_thread;
        }
    };


    //---------------------------------------------------------------------
    // Dispatch entrypoints
    //---------------------------------------------------------------------

    /**
     * Internal dispatch routine for computing a device-wide reduction using the
     * specified kernel functions.
     *
     * If the input is larger than a single tile, this method uses two-passes of
     * kernel invocations.
     */
    template <
        typename                Spmv1ColKernelT,                    ///< Function type of cub::DeviceSpmv1ColKernel
        typename                SpmvSearchKernelT,                  ///< Function type of cub::AgentSpmvSearchKernel
        typename                SpmvKernelT,                        ///< Function type of cub::AgentSpmvKernel
        typename                SegmentFixupKernelT>                ///< Function type of cub::DeviceSegmentFixupKernelT
    CUB_RUNTIME_FUNCTION __forceinline__
    static cudaError_t Dispatch(
        void*                   d_temp_storage,                     ///< [in] Device-accessible allocation of temporary storage.  When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
        size_t&                 temp_storage_bytes,                 ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
        SpmvParamsT&            spmv_params,                        ///< SpMV input parameter bundle
        cudaStream_t            stream,                             ///< [in] CUDA stream to launch kernels within.  Default is stream<sub>0</sub>.
        bool                    debug_synchronous,                  ///< [in] Whether or not to synchronize the stream after every kernel launch to check for errors.  Also causes launch configurations to be printed to the console.  Default is \p false.
        Spmv1ColKernelT         spmv_1col_kernel,                   ///< [in] Kernel function pointer to parameterization of DeviceSpmv1ColKernel
        SpmvSearchKernelT       spmv_search_kernel,                 ///< [in] Kernel function pointer to parameterization of AgentSpmvSearchKernel
        SpmvKernelT             spmv_kernel,                        ///< [in] Kernel function pointer to parameterization of AgentSpmvKernel
        SegmentFixupKernelT     segment_fixup_kernel,               ///< [in] Kernel function pointer to parameterization of cub::DeviceSegmentFixupKernel
        KernelConfig            spmv_config,                        ///< [in] Dispatch parameters that match the policy that \p spmv_kernel was compiled for
        KernelConfig            segment_fixup_config)               ///< [in] Dispatch parameters that match the policy that \p segment_fixup_kernel was compiled for
    {
#ifndef CUB_RUNTIME_ENABLED

        // Kernel launch not supported from this device
        return CubDebug(cudaErrorNotSupported );

#else
        cudaError error = cudaSuccess;
        do
        {
            if (spmv_params.num_rows < 0 || spmv_params.num_cols < 0)
            {
              return cudaErrorInvalidValue;
            }

            if (spmv_params.num_rows == 0 || spmv_params.num_cols == 0)
            { // Empty problem, no-op.
                if (d_temp_storage == NULL)
                {
                    temp_storage_bytes = 1;
                }

                break;
            }

            if (spmv_params.num_cols == 1)
            {
                if (d_temp_storage == NULL)
                {
                    // Return if the caller is simply requesting the size of the storage allocation
                    temp_storage_bytes = 1;
                    break;
                }

                // Get search/init grid dims
                int degen_col_kernel_block_size = INIT_KERNEL_THREADS;
                int degen_col_kernel_grid_size = cub::DivideAndRoundUp(spmv_params.num_rows, degen_col_kernel_block_size);

                if (debug_synchronous) _CubLog("Invoking spmv_1col_kernel<<<%d, %d, 0, %lld>>>()\n",
                    degen_col_kernel_grid_size, degen_col_kernel_block_size, (long long) stream);

                // Invoke spmv_search_kernel
                THRUST_NS_QUALIFIER::cuda_cub::launcher::triple_chevron(
                    degen_col_kernel_grid_size, degen_col_kernel_block_size, 0,
                    stream
                ).doit(spmv_1col_kernel,
                    spmv_params);

                // Check for failure to launch
                if (CubDebug(error = cudaPeekAtLastError())) break;

                // Sync the stream if specified to flush runtime errors
                if (debug_synchronous && (CubDebug(error = SyncStream(stream)))) break;

                break;
            }

            // Get device ordinal
            int device_ordinal;
            if (CubDebug(error = cudaGetDevice(&device_ordinal))) break;

            // Get SM count
            int sm_count;
            if (CubDebug(error = cudaDeviceGetAttribute (&sm_count, cudaDevAttrMultiProcessorCount, device_ordinal))) break;

            // Get max x-dimension of grid
            int max_dim_x;
            if (CubDebug(error = cudaDeviceGetAttribute(&max_dim_x, cudaDevAttrMaxGridDimX, device_ordinal))) break;

            // Total number of spmv work items
            int num_merge_items = spmv_params.num_rows + spmv_params.num_nonzeros;

            // Tile sizes of kernels
            int merge_tile_size              = spmv_config.block_threads * spmv_config.items_per_thread;
            int segment_fixup_tile_size     = segment_fixup_config.block_threads * segment_fixup_config.items_per_thread;

            // Number of tiles for kernels
            int num_merge_tiles            = cub::DivideAndRoundUp(num_merge_items, merge_tile_size);
            int num_segment_fixup_tiles    = cub::DivideAndRoundUp(num_merge_tiles, segment_fixup_tile_size);

            // Get SM occupancy for kernels
            int spmv_sm_occupancy;
            if (CubDebug(error = MaxSmOccupancy(
                spmv_sm_occupancy,
                spmv_kernel,
                spmv_config.block_threads))) break;

            int segment_fixup_sm_occupancy;
            if (CubDebug(error = MaxSmOccupancy(
                segment_fixup_sm_occupancy,
                segment_fixup_kernel,
                segment_fixup_config.block_threads))) break;

            // Get grid dimensions
            dim3 spmv_grid_size(
                CUB_MIN(num_merge_tiles, max_dim_x),
                cub::DivideAndRoundUp(num_merge_tiles, max_dim_x),
                1);

            dim3 segment_fixup_grid_size(
                CUB_MIN(num_segment_fixup_tiles, max_dim_x),
                cub::DivideAndRoundUp(num_segment_fixup_tiles, max_dim_x),
                1);

            // Get the temporary storage allocation requirements
            size_t allocation_sizes[3];
            if (CubDebug(error = ScanTileStateT::AllocationSize(num_segment_fixup_tiles, allocation_sizes[0]))) break;    // bytes needed for reduce-by-key tile status descriptors
            allocation_sizes[1] = num_merge_tiles * sizeof(KeyValuePairT);       // bytes needed for block carry-out pairs
            allocation_sizes[2] = (num_merge_tiles + 1) * sizeof(CoordinateT);   // bytes needed for tile starting coordinates

            // Alias the temporary allocations from the single storage blob (or compute the necessary size of the blob)
            void* allocations[3] = {};
            if (CubDebug(error = AliasTemporaries(d_temp_storage, temp_storage_bytes, allocations, allocation_sizes))) break;
            if (d_temp_storage == NULL)
            {
                // Return if the caller is simply requesting the size of the storage allocation
                break;
            }

            // Construct the tile status interface
            ScanTileStateT tile_state;
            if (CubDebug(error = tile_state.Init(num_segment_fixup_tiles, allocations[0], allocation_sizes[0]))) break;

            // Alias the other allocations
            KeyValuePairT*  d_tile_carry_pairs      = (KeyValuePairT*) allocations[1];  // Agent carry-out pairs
            CoordinateT*    d_tile_coordinates      = (CoordinateT*) allocations[2];    // Agent starting coordinates

            // Get search/init grid dims
            int search_block_size   = INIT_KERNEL_THREADS;
            int search_grid_size    = cub::DivideAndRoundUp(num_merge_tiles + 1, search_block_size);

            if (search_grid_size < sm_count)
//            if (num_merge_tiles < spmv_sm_occupancy * sm_count)
            {
                // Not enough spmv tiles to saturate the device: have spmv blocks search their own staring coords
                d_tile_coordinates = NULL;
            }
            else
            {
                // Use separate search kernel if we have enough spmv tiles to saturate the device

                // Log spmv_search_kernel configuration
                if (debug_synchronous) _CubLog("Invoking spmv_search_kernel<<<%d, %d, 0, %lld>>>()\n",
                    search_grid_size, search_block_size, (long long) stream);

                // Invoke spmv_search_kernel
                THRUST_NS_QUALIFIER::cuda_cub::launcher::triple_chevron(
                    search_grid_size, search_block_size, 0, stream
                ).doit(spmv_search_kernel,
                    num_merge_tiles,
                    d_tile_coordinates,
                    spmv_params);

                // Check for failure to launch
                if (CubDebug(error = cudaPeekAtLastError())) break;

                // Sync the stream if specified to flush runtime errors
                if (debug_synchronous && (CubDebug(error = SyncStream(stream)))) break;
            }

            // Log spmv_kernel configuration
            if (debug_synchronous) _CubLog("Invoking spmv_kernel<<<{%d,%d,%d}, %d, 0, %lld>>>(), %d items per thread, %d SM occupancy\n",
                spmv_grid_size.x, spmv_grid_size.y, spmv_grid_size.z, spmv_config.block_threads, (long long) stream, spmv_config.items_per_thread, spmv_sm_occupancy);

            // Invoke spmv_kernel
            THRUST_NS_QUALIFIER::cuda_cub::launcher::triple_chevron(
                spmv_grid_size, spmv_config.block_threads, 0, stream
            ).doit(spmv_kernel,
                spmv_params,
                d_tile_coordinates,
                d_tile_carry_pairs,
                num_merge_tiles,
                tile_state,
                num_segment_fixup_tiles);

            // Check for failure to launch
            if (CubDebug(error = cudaPeekAtLastError())) break;

            // Sync the stream if specified to flush runtime errors
            if (debug_synchronous && (CubDebug(error = SyncStream(stream)))) break;

            // Run reduce-by-key fixup if necessary
            if (num_merge_tiles > 1)
            {
                // Log segment_fixup_kernel configuration
                if (debug_synchronous) _CubLog("Invoking segment_fixup_kernel<<<{%d,%d,%d}, %d, 0, %lld>>>(), %d items per thread, %d SM occupancy\n",
                    segment_fixup_grid_size.x, segment_fixup_grid_size.y, segment_fixup_grid_size.z, segment_fixup_config.block_threads, (long long) stream, segment_fixup_config.items_per_thread, segment_fixup_sm_occupancy);

                // Invoke segment_fixup_kernel
                THRUST_NS_QUALIFIER::cuda_cub::launcher::triple_chevron(
                    segment_fixup_grid_size, segment_fixup_config.block_threads,
                    0, stream
                ).doit(segment_fixup_kernel,
                    d_tile_carry_pairs,
                    spmv_params.d_vector_y,
                    num_merge_tiles,
                    num_segment_fixup_tiles,
                    tile_state);

                // Check for failure to launch
                if (CubDebug(error = cudaPeekAtLastError())) break;

                // Sync the stream if specified to flush runtime errors
                if (debug_synchronous && (CubDebug(error = SyncStream(stream)))) break;
            }
        }
        while (0);

        return error;

#endif // CUB_RUNTIME_ENABLED
    }


    /**
     * Internal dispatch routine for computing a device-wide reduction
     */
    CUB_RUNTIME_FUNCTION __forceinline__
    static cudaError_t Dispatch(
        void*                   d_temp_storage,                     ///< [in] Device-accessible allocation of temporary storage.  When NULL, the required allocation size is written to \p temp_storage_bytes and no work is done.
        size_t&                 temp_storage_bytes,                 ///< [in,out] Reference to size in bytes of \p d_temp_storage allocation
        SpmvParamsT&            spmv_params,                        ///< SpMV input parameter bundle
        cudaStream_t            stream                  = 0,        ///< [in] <b>[optional]</b> CUDA stream to launch kernels within.  Default is stream<sub>0</sub>.
        bool                    debug_synchronous       = false)    ///< [in] <b>[optional]</b> Whether or not to synchronize the stream after every kernel launch to check for errors.  May cause significant slowdown.  Default is \p false.
    {
        cudaError error = cudaSuccess;
        do
        {
            // Get PTX version
            int ptx_version = 0;
            if (CubDebug(error = PtxVersion(ptx_version))) break;

            // Get kernel kernel dispatch configurations
            KernelConfig spmv_config, segment_fixup_config;
            InitConfigs(ptx_version, spmv_config, segment_fixup_config);

            if (CubDebug(error = Dispatch(
                d_temp_storage, temp_storage_bytes, spmv_params, stream, debug_synchronous,
                DeviceSpmv1ColKernel<PtxSpmvPolicyT, ValueT, OffsetT>,
                DeviceSpmvSearchKernel<PtxSpmvPolicyT, OffsetT, CoordinateT, SpmvParamsT>,
                DeviceSpmvKernel<PtxSpmvPolicyT, ScanTileStateT, ValueT, OffsetT, CoordinateT, false, false>,
                DeviceSegmentFixupKernel<PtxSegmentFixupPolicy, KeyValuePairT*, ValueT*, OffsetT, ScanTileStateT>,
                spmv_config, segment_fixup_config))) break;

        }
        while (0);

        return error;
    }
};


CUB_NAMESPACE_END


