src/gpu/pannotia/pagerank/kernel_spmv.h

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#ifndef KERNEL_SPMV_H
#define KERNEL_SPMV_H

#include "hip/hip_runtime.h"

/**
 * @brief   inibuffer
 * @param   page_rank1   PageRank array 1
 * @param   page_rank2   PageRank array 2
 * @param   num_nodes    number of vertices
 */
__global__ void
inibuffer(float *page_rank1, float *page_rank2, const int num_nodes)
{
    // Get my workitem id
    int tid = blockDim.x * blockIdx.x + threadIdx.x;
    // Initialize two pagerank arrays
    if (tid < num_nodes) {
        page_rank1[tid] = 1 / (float)num_nodes;
        page_rank2[tid] = 0.0f;
    }
}

/**
 * @brief   inicsr
 * @param   row        csr pointer array
 * @param   col        csr col array
 * @param   data       csr weigh array
 * @param   col_cnt    array for #. out-going edges
 * @param   num_nodes  number of vertices
 * @param   num_edges  number of edges
 */
__global__ void
inicsr(int *row, int *col, float *data, int *col_cnt, int num_nodes,
       int num_edges)
{
    // Get my workitem id
    int tid = blockDim.x * blockIdx.x + threadIdx.x;
    if (tid < num_nodes) {
        // Get the starting and ending pointers
        int start = row[tid];
        int end;
        if (tid + 1 < num_nodes) {
            end = row[tid + 1] ;
        } else {
            end = num_edges;
        }

        int nid;
        // Navigate one row of data
        for (int edge = start; edge < end; edge++) {
            nid = col[edge];
            // Each neighbor will get equal amount of pagerank
            data[edge] = 1.0 / (float)col_cnt[nid];
        }
    }
}

/**
 * @brief   spmv_csr_scalar_kernel (simple spmv)
 * @param   num_nodes  number of vertices
 * @param   row        csr pointer array
 * @param   col        csr col array
 * @param   data       csr weigh array
 * @param   x          input vector
 * @param   y          output vector
 */
__global__ void
spmv_csr_scalar_kernel(const int num_nodes, int *row, int *col, float *data,
                       float *x, float *y)
{
    // Get my workitem id
    int tid = blockDim.x * blockIdx.x + threadIdx.x;
    if (tid < num_nodes) {
        // Get the start and end pointers
        int row_start = row[tid];
        int row_end = row[tid + 1];
        float sum = 0;
        //navigate one row and sum all the elements
        for (int j = row_start; j < row_end; j++) {
            sum += data[j] * x[col[j]];
        }
        y[tid] += sum;
    }
}

/**
 * @brief   pagerank2
 * @param   page_rank1   PageRank array 1
 * @param   page_rank2   PageRank array 2
 * @param   num_nodes    number of vertices
 */
__global__ void
pagerank2(float *page_rank1, float *page_rank2, const int num_nodes)
{
    // Get my workitem id
    int tid = blockDim.x * blockIdx.x + threadIdx.x;
    // Update pagerank value with damping factor
    if (tid < num_nodes) {
        page_rank1[tid]	= 0.15f / (float)num_nodes + 0.85f * page_rank2[tid];
        page_rank2[tid] = 0.0f;
    }
}

#endif // KERNEL_SPMV_H