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

#pragma once

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

#include "dispatch/dispatch_spmv_orig.cuh"
#include "../util_namespace.cuh"

/// Optional outer namespace(s)
CUB_NS_PREFIX

/// CUB namespace
namespace cub {


/**
 * \brief DeviceSpmv provides device-wide parallel operations for performing sparse-matrix * dense-vector multiplication (SpMV).
 * \ingroup SingleModule
 *
 * \par Overview
 * The [<em>SpMV computation</em>](http://en.wikipedia.org/wiki/Sparse_matrix-vector_multiplication)
 * performs the matrix-vector operation
 * <em>y</em> = <em>alpha</em>*<b>A</b>*<em>x</em> + <em>beta</em>*<em>y</em>,
 * where:
 *  - <b>A</b> is an <em>m</em>x<em>n</em> sparse matrix whose non-zero structure is specified in
 *    [<em>compressed-storage-row (CSR) format</em>](http://en.wikipedia.org/wiki/Sparse_matrix#Compressed_row_Storage_.28CRS_or_CSR.29)
 *    (i.e., three arrays: <em>values</em>, <em>row_offsets</em>, and <em>column_indices</em>)
 *  - <em>x</em> and <em>y</em> are dense vectors
 *  - <em>alpha</em> and <em>beta</em> are scalar multiplicands
 *
 * \par Usage Considerations
 * \cdp_class{DeviceSpmv}
 *
 */
struct DeviceSpmv
{
    /******************************************************************//**
     * \name CSR matrix operations
     *********************************************************************/
    //@{

    /**
     * \brief This function performs the matrix-vector operation <em>y</em> = <b>A</b>*<em>x</em>.
     *
     * \par Snippet
     * The code snippet below illustrates SpMV upon a 9x9 CSR matrix <b>A</b>
     * representing a 3x3 lattice (24 non-zeros).
     *
     * \par
     * \code
     * #include <cub/cub.cuh>   // or equivalently <cub/device/device_spmv.cuh>
     *
     * // Declare, allocate, and initialize device-accessible pointers for input matrix A, input vector x,
     * // and output vector y
     * int    num_rows = 9;
     * int    num_cols = 9;
     * int    num_nonzeros = 24;
     *
     * float* d_values;  // e.g., [1, 1, 1, 1, 1, 1, 1, 1,
     *                   //        1, 1, 1, 1, 1, 1, 1, 1,
     *                   //        1, 1, 1, 1, 1, 1, 1, 1]
     *
     * int*   d_column_indices; // e.g., [1, 3, 0, 2, 4, 1, 5, 0,
     *                          //        4, 6, 1, 3, 5, 7, 2, 4,
     *                          //        8, 3, 7, 4, 6, 8, 5, 7]
     *
     * int*   d_row_offsets;    // e.g., [0, 2, 5, 7, 10, 14, 17, 19, 22, 24]
     *
     * float* d_vector_x;       // e.g., [1, 1, 1, 1, 1, 1, 1, 1, 1]
     * float* d_vector_y;       // e.g., [ ,  ,  ,  ,  ,  ,  ,  ,  ]
     * ...
     *
     * // Determine temporary device storage requirements
     * void*    d_temp_storage = NULL;
     * size_t   temp_storage_bytes = 0;
     * cub::DeviceSpmv::CsrMV(d_temp_storage, temp_storage_bytes, d_values,
     *     d_row_offsets, d_column_indices, d_vector_x, d_vector_y,
     *     num_rows, num_cols, num_nonzeros, alpha, beta);
     *
     * // Allocate temporary storage
     * cudaMalloc(&d_temp_storage, temp_storage_bytes);
     *
     * // Run SpMV
     * cub::DeviceSpmv::CsrMV(d_temp_storage, temp_storage_bytes, d_values,
     *     d_row_offsets, d_column_indices, d_vector_x, d_vector_y,
     *     num_rows, num_cols, num_nonzeros, alpha, beta);
     *
     * // d_vector_y <-- [2, 3, 2, 3, 4, 3, 2, 3, 2]
     *
     * \endcode
     *
     * \tparam ValueT       <b>[inferred]</b> Matrix and vector value type (e.g., /p float, /p double, etc.)
     */
    template <
        typename            ValueT>
    CUB_RUNTIME_FUNCTION
    static cudaError_t CsrMV(
        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
        ValueT*             d_values,                           ///< [in] Pointer to the array of \p num_nonzeros values of the corresponding nonzero elements of matrix <b>A</b>.
        int*                d_row_offsets,                      ///< [in] Pointer to the array of \p m + 1 offsets demarcating the start of every row in \p d_column_indices and \p d_values (with the final entry being equal to \p num_nonzeros)
        int*                d_column_indices,                   ///< [in] Pointer to the array of \p num_nonzeros column-indices of the corresponding nonzero elements of matrix <b>A</b>.  (Indices are zero-valued.)
        ValueT*             d_vector_x,                         ///< [in] Pointer to the array of \p num_cols values corresponding to the dense input vector <em>x</em>
        ValueT*             d_vector_y,                         ///< [out] Pointer to the array of \p num_rows values corresponding to the dense output vector <em>y</em>
        int                 num_rows,                           ///< [in] number of rows of matrix <b>A</b>.
        int                 num_cols,                           ///< [in] number of columns of matrix <b>A</b>.
        int                 num_nonzeros,                       ///< [in] number of nonzero elements of matrix <b>A</b>.
        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.
    {
        SpmvParams<ValueT, int> spmv_params;
        spmv_params.d_values             = d_values;
        spmv_params.d_row_end_offsets    = d_row_offsets + 1;
        spmv_params.d_column_indices     = d_column_indices;
        spmv_params.d_vector_x           = d_vector_x;
        spmv_params.d_vector_y           = d_vector_y;
        spmv_params.num_rows             = num_rows;
        spmv_params.num_cols             = num_cols;
        spmv_params.num_nonzeros         = num_nonzeros;
        spmv_params.alpha                = 1.0;
        spmv_params.beta                 = 0.0;

        return DispatchSpmv<ValueT, int>::Dispatch(
            d_temp_storage,
            temp_storage_bytes,
            spmv_params,
            stream,
            debug_synchronous);
    }

    //@}  end member group
};



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