/************************************************************************************\
 *                                                                                  *
 * 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                           *
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\************************************************************************************/

#ifndef KERNEL_H
#define KERNEL_H

#include "hip/hip_runtime.h"

#define BIGNUM 99999999

/**
* init kernel
* @param s_array   set array
* @param c_array   status array
* @param cu_array  status update array
* @param num_nodes number of vertices
* @param num_edges number of edges
*/
__global__ void
init(int *s_array, int *c_array, int *cu_array, int num_nodes, int num_edges)
{
    // Get my workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;
    if (tid < num_nodes) {
        // Set the status array: not processed
        c_array[tid] = -1;
        cu_array[tid] = -1;
        s_array[tid] = 0;
    }
}

/**
* mis1 kernel
* @param row          csr pointer array
* @param col          csr column index array
* @param node_value   node value array
* @param s_array      set array
* @param c_array node status array
* @param min_array    node value array
* @param stop node    value array
* @param num_nodes    number of vertices
* @param num_edges    number of edges
*/
__global__ void
mis1(int *row, int *col, int *node_value, int *s_array, int *c_array,
     int *min_array, int *stop, int num_nodes, int num_edges)
{
    // Get workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;
    if (tid < num_nodes) {
        // If the vertex is not processed
        if (c_array[tid] == -1) {
            *stop = 1;
            // Get the start and end pointers
            int start = row[tid];
            int end;
            if (tid + 1 < num_nodes) {
                end = row[tid + 1];
            } else {
                end = num_edges;
            }

            // Navigate the neighbor list and find the min
            int min = BIGNUM;
            for (int edge = start; edge < end; edge++) {
                if (c_array[col[edge]] == -1) {
                    if (node_value[col[edge]] < min) {
                        min = node_value[col[edge]];
                    }
                }
            }
            min_array[tid] = min;
        }
    }
}

/**
* mis2 kernel
* @param row          csr pointer array
* @param col          csr column index array
* @param node_value   node value array
* @param s_array      set array
* @param c_array      status array
* @param cu_array     status update array
* @param min_array    node value array
* @param num_nodes    number of vertices
* @param num_edges    number of edges
*/
__global__ void
mis2(int *row, int *col, int *node_value, int *s_array, int *c_array,
     int *cu_array, int *min_array, int num_nodes, int num_edges)
{
    // Get my workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;

    if (tid < num_nodes) {
        if (node_value[tid] <= min_array[tid]  && c_array[tid] == -1) {
            // -1: Not processed -2: Inactive 2: Independent set
            // Put the item into the independent set
            s_array[tid] = 2;

            // Get the start and end pointers
            int start = row[tid];
            int end;

            if (tid + 1 < num_nodes) {
                end = row[tid + 1];
            } else {
                end = num_edges;
            }

            // Set the status to inactive
            c_array[tid] = -2;

            // Mark all the neighbors inactive
            for (int edge = start; edge < end; edge++) {
                if (c_array[col[edge]] == -1) {
                    //use status update array to avoid race
                    cu_array[col[edge]] = -2;
                }
            }
        }
    }
}

/**
* mis3 kernel
* @param cu_array     status update array
* @param  c_array     status array
* @param num_nodes    number of vertices
*/
__global__ void
mis3(int *cu_array, int *c_array, int num_nodes)
{
    //get my workitem id
    int tid = hipBlockDim_x * hipBlockIdx_x + hipThreadIdx_x;

    //set the status array
    if (tid < num_nodes && cu_array[tid] == -2) {
        c_array[tid] = cu_array[tid];
    }
}

#endif // KERNEL_H