grid_even_share.cuh

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/******************************************************************************
 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
 * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
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#pragma once

#include "../util_namespace.cuh"
#include "../util_macro.cuh"
#include "grid_mapping.cuh"

CUB_NS_PREFIX

namespace cub {


template <typename OffsetT>
struct GridEvenShare
{
private:

    OffsetT     total_tiles;
    int         big_shares;
    OffsetT     big_share_items;
    OffsetT     normal_share_items;
    OffsetT     normal_base_offset;

public:

    OffsetT     num_items;

    int         grid_size;

    OffsetT     block_offset;

    OffsetT     block_end;

    OffsetT     block_stride;


    __host__ __device__ __forceinline__ GridEvenShare() :
        total_tiles(0),
        big_shares(0),
        big_share_items(0),
        normal_share_items(0),
        normal_base_offset(0),
        num_items(0),
        grid_size(0),
        block_offset(0),
        block_end(0),
        block_stride(0)
    {}


    __host__ __device__ __forceinline__ void DispatchInit(
        OffsetT num_items,          
        int     max_grid_size,      
        int     tile_items)         
    {
        this->block_offset          = num_items;    // Initialize past-the-end
        this->block_end             = num_items;    // Initialize past-the-end
        this->num_items             = num_items;
        this->total_tiles           = (num_items + tile_items - 1) / tile_items;
        this->grid_size             = CUB_MIN(total_tiles, max_grid_size);
        OffsetT avg_tiles_per_block = total_tiles / grid_size;
        this->big_shares            = total_tiles - (avg_tiles_per_block * grid_size);        // leftover grains go to big blocks
        this->normal_share_items    = avg_tiles_per_block * tile_items;
        this->normal_base_offset    = big_shares * tile_items;
        this->big_share_items       = normal_share_items + tile_items;
    }


    template <int TILE_ITEMS>
    __device__ __forceinline__ void BlockInit(
        int block_id,
        Int2Type<GRID_MAPPING_RAKE> /*strategy_tag*/)
    {
        block_stride = TILE_ITEMS;
        if (block_id < big_shares)
        {
            // This thread block gets a big share of grains (avg_tiles_per_block + 1)
            block_offset = (block_id * big_share_items);
            block_end = block_offset + big_share_items;
        }
        else if (block_id < total_tiles)
        {
            // This thread block gets a normal share of grains (avg_tiles_per_block)
            block_offset = normal_base_offset + (block_id * normal_share_items);
            block_end = CUB_MIN(num_items, block_offset + normal_share_items);
        }
        // Else default past-the-end
    }


    template <int TILE_ITEMS>
    __device__ __forceinline__ void BlockInit(
        int block_id,
        Int2Type<GRID_MAPPING_STRIP_MINE> /*strategy_tag*/)
    {
        block_stride = grid_size * TILE_ITEMS;
        block_offset = (block_id * TILE_ITEMS);
        block_end = num_items;
    }


    template <
        int TILE_ITEMS,
        GridMappingStrategy STRATEGY>
    __device__ __forceinline__ void BlockInit()
    {
        BlockInit<TILE_ITEMS>(blockIdx.x, Int2Type<STRATEGY>());
    }


    template <int TILE_ITEMS>
    __device__ __forceinline__ void BlockInit(
        OffsetT block_offset,                       
        OffsetT block_end)                          
    {
        this->block_offset = block_offset;
        this->block_end = block_end;
        this->block_stride = TILE_ITEMS;
    }


};




       // end group GridModule

}               // CUB namespace
CUB_NS_POSTFIX  // Optional outer namespace(s)