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c:mpi:wave-algorithm-leader-election-spanning-tree [2024/01/19 13:42] – removed - external edit (Unknown date) 127.0.0.1c:mpi:wave-algorithm-leader-election-spanning-tree [2024/01/19 13:42] (current) – ↷ Page name changed from c:mpi:rwave-algorithm-leader-election-spanning-tree to c:mpi:wave-algorithm-leader-election-spanning-tree odefta
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 +====== MPI Wave algorithm with leader election and spanning tree construction ======
 +
 +Implementing a wave algorithm with leader election and spanning tree construction in MPI is a complex task that involves multiple phases: **leader election** using a heartbeat algorithm, constructing a **spanning tree**, and optionally, **broadcasting the tree structure** to all nodes. 
 +
 +The following implementation assumes a simple network where each process can communicate directly with any other process. In a real-world scenario, the network topology might be more complex, affecting how processes communicate.
 +
 +<code c mpi-wave-algorithm-advanced.c>
 +#include <mpi.h>
 +#include <stdio.h>
 +#include <stdlib.h>
 +#include <limits.h>
 +
 +#define MAX_ITERATIONS 5
 +
 +int main(int argc, char** argv) {
 +    MPI_Init(&argc, &argv);
 +
 +    int world_rank, world_size;
 +    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
 +    MPI_Comm_size(MPI_COMM_WORLD, &world_size);
 +
 +    // Phase 1: Leader Election
 +    int leader = world_rank;
 +    for (int iteration = 0; iteration < MAX_ITERATIONS; iteration++) {
 +        for (int i = 0; i < world_size; i++) {
 +            if (i != world_rank) {
 +                MPI_Send(&leader, 1, MPI_INT, i, 0, MPI_COMM_WORLD);
 +                int received_leader;
 +                MPI_Recv(&received_leader, 1, MPI_INT, i, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
 +                if (received_leader > leader) {
 +                    leader = received_leader;
 +                }
 +            }
 +        }
 +    }
 +
 +    // Phase 2: Spanning Tree Construction
 +    int parent = -1;
 +    if (world_rank == leader) {
 +        for (int i = 0; i < world_size; i++) {
 +            if (i != leader) {
 +                MPI_Send(&leader, 1, MPI_INT, i, 0, MPI_COMM_WORLD);
 +            }
 +        }
 +    } else {
 +        MPI_Recv(&parent, 1, MPI_INT, MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
 +        for (int i = 0; i < world_size; i++) {
 +            if (i != world_rank && i != parent) {
 +                MPI_Send(&leader, 1, MPI_INT, i, 0, MPI_COMM_WORLD);
 +            }
 +        }
 +    }
 +
 +    // Phase 3: Broadcasting the Tree Structure (Optional)
 +    int* tree = malloc(world_size * sizeof(int));
 +    if (world_rank == leader) {
 +        // Initialize tree structure
 +        for (int i = 0; i < world_size; i++) {
 +            tree[i] = -1; // -1 indicates no parent
 +        }
 +    } else {
 +        MPI_Recv(tree, world_size, MPI_INT, parent, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
 +    }
 +    tree[world_rank] = parent;
 +
 +    // Propagate the tree structure to children
 +    for (int i = 0; i < world_size; i++) {
 +        if (i != world_rank && i != parent) {
 +            MPI_Send(tree, world_size, MPI_INT, i, 0, MPI_COMM_WORLD);
 +        }
 +    }
 +
 +    // Display the tree structure
 +    printf("Process %d: Leader is %d, Parent is %d\n", world_rank, leader, tree[world_rank]);
 +    for (int i = 0; i < world_size; i++) {
 +        printf("Process %d: Parent of %d is %d\n", world_rank, i, tree[i]);
 +    }
 +
 +    free(tree);
 +    MPI_Finalize();
 +    return 0;
 +}
 +</code>
 +
 +**Leader Election**: Each process sends and receives leader values to determine the global leader.
 +
 +**Spanning Tree Construction**: The leader initiates the spanning tree construction. Each node sets its parent and forwards the message to other nodes.
 +
 +**Broadcasting the Tree**: The leader initializes the tree structure and sends it to its children. Each node then propagates this structure down the tree.
 +
 +The output will display the leader and parent of each process, along with the spanning tree structure.
 +
 +<note>
 +This is a simplified and idealized implementation. Practical distributed systems may need to handle various complexities such as network failures, dynamic joining and leaving of nodes, and non-uniform communication delays.
 +</note>