/************************************************************************************\
 *                                                                                  *
 * Copyright � 2014 Advanced Micro Devices, Inc.                                    *
 * Copyright (c) 2015 Mark D. Hill and David A. Wood                                *
 * Copyright (c) 2021 Gaurav Jain and Matthew D. Sinclair                           *
 * All rights reserved.                                                             *
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\************************************************************************************/

#ifndef KERNEL_H
#define KERNEL_H

#include "hip/hip_runtime.h"

/**
 * @brief   pagerank 1
 * @param   row         csr pointer array
 * @param   col         csr column array
 * @param   data        weight array
 * @param   page_rank1  pagerank array 1
 * @param   page_rank2  pagerank array 2
 * @param   num_nodes   number of vertices
 * @param   num_edges   number of edges
 */
__global__ void
pagerank1(int *row, int *col, int *data, float *page_rank1, float *page_rank2,
          const int num_nodes, const int num_edges)
{
    // Get my workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;

    if (tid < num_nodes) {
        // Get the starting and ending pointers of the neighborlist
        int start = row[tid];
        int end;
        if (tid + 1 < num_nodes) {
            end = row[tid + 1];
        } else {
            end = num_edges;
        }

        int nid;
        // Navigate the neighbor list
        for (int edge = start; edge < end; edge++) {
            nid = col[edge];
            // Transfer the PageRank value to neighbors
            atomicAdd(&page_rank2[nid], page_rank1[tid] / (float)(end - start));
        }
    }
}

/**
 * @brief   pagerank 2
 * @param   row         csr pointer array
 * @param   col         csr column array
 * @param   data        weight array
 * @param   page_rank1  pagerank array 1
 * @param   page_rank2  pagerank array 2
 * @param   num_nodes   number of vertices
 * @param   num_edges   number of edges
 */
__global__ void
pagerank2(int *row, int *col, int *data, float *page_rank1, float *page_rank2,
          const int num_nodes, const int num_edges)
{
    // Get my workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;

    // Update pagerank value with the damping factor
    if (tid < num_nodes) {
        page_rank1[tid]	= 0.15 / (float)num_nodes + 0.85 * page_rank2[tid];
        page_rank2[tid] = 0.0f;
    }
}

/**
 * @brief   inibuffer
 * @param   row         csr pointer array
 * @param   page_rank1  pagerank array 1
 * @param   page_rank2  pagerank array 2
 * @param   num_nodes   number of vertices
 */
__global__ void
inibuffer(int *row, float *page_rank1, float *page_rank2, const int num_nodes,
          const int num_edges)
{
    // Get my thread id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;

    if (tid < num_nodes) {
        page_rank1[tid] = 1 / (float)num_nodes;
        page_rank2[tid] = 0.0f;
    }
}

#endif // KERNEL_H