skalar

#include<stdio.h>
#include<stdlib.h>
#include<mpi.h>

void get_dims(int *n_p, int *local_n_p, int my_rank, int comm_sz, MPI_Comm comm);
void allocate(double **local_a_pp, double **local_b_pp, double **local_c_pp, int n, int local_n, MPI_Comm comm);
void read_vector(double local_vector[], int n, int local_n, int my_rank, MPI_Comm comm);
void print_vector(double local_vector[], int n, int local_n, int my_rank, MPI_Comm comm);
void multiply(double local_a[], double local_b[], double local_c[], double* local_sum, int local_n);
void print_sum(double local_sum, double global_sum, int my_rank, MPI_Comm comm);

int main(void) {
    int comm_sz, my_rank, n, local_n;
    double local_sum = 0.0; double global_sum = 0.0;
    double* local_a; double* local_b; double* local_c;
    MPI_Comm comm;

    MPI_Init(NULL, NULL);
    comm = MPI_COMM_WORLD;
    MPI_Comm_size(comm, &comm_sz);
    MPI_Comm_rank(comm, &my_rank);

    get_dims(&n, &local_n, my_rank, comm_sz, comm);
    allocate(&local_a, &local_b, &local_c, n, local_n, comm);

    read_vector(local_a, n, local_n, my_rank, comm);
    print_vector(local_a, n, local_n, my_rank, comm);

    read_vector(local_b, n, local_n, my_rank, comm);
    print_vector(local_b, n, local_n, my_rank, comm);

    multiply(local_a, local_b, local_c, &local_sum, local_n);
    print_vector(local_c, n, local_n, my_rank, comm);
    print_sum(local_sum, global_sum, my_rank, comm);

    free(local_a); free(local_b); free(local_c);
    MPI_Finalize();

    return 0;
}

void get_dims(int *n_p, int *local_n_p, int my_rank, int comm_sz, MPI_Comm comm) {
    if (my_rank == 0) {
        printf("Unesite velicinu vektora - n: \n");
        scanf("%d", n_p);
    }
    MPI_Bcast(n_p, 1, MPI_INT, 0, comm);

    if (*n_p <= 0 || *n_p % comm_sz != 0) {
        if (my_rank == 0) {
            fprintf(stderr, "Proc %d > In %s, %s\n", my_rank, "get_dims", "input invalid.");
            fflush(stderr);
        }
        MPI_Finalize();
        exit(-1);
    }


    *local_n_p = *n_p / comm_sz;
}

void allocate(double **local_a_pp, double **local_b_pp, double **local_c_pp, int n, int local_n, MPI_Comm comm) {
    *local_a_pp = calloc(local_n, sizeof(double));
    *local_b_pp = calloc(local_n, sizeof(double));
    *local_c_pp = calloc(local_n, sizeof(double));
}

void read_vector(double local_vector[], int n, int local_n, int my_rank, MPI_Comm comm) {
    double* vector = NULL;
    if (my_rank == 0) {
        vector = calloc(n, sizeof(double));
        printf("Enter the vector:\n");
        for (int i = 0; i < n; i++)
            scanf("%lf", &vector[i]);

        MPI_Scatter(vector, local_n, MPI_DOUBLE, local_vector, local_n, MPI_DOUBLE, 0, comm);
        free(vector);
    } else {
        MPI_Scatter(vector, local_n, MPI_DOUBLE, local_vector, local_n, MPI_DOUBLE, 0, comm);
    }
}

void print_vector(double local_vector[], int n, int local_n, int my_rank, MPI_Comm comm) {
    double* vector = NULL;
    if (my_rank == 0) {
        vector = calloc(n, sizeof(double));
        MPI_Gather(local_vector, local_n, MPI_DOUBLE, vector, local_n, MPI_DOUBLE, 0, comm);

        printf("\nVector: [ ");
        for (int i = 0; i < n; i++)
            printf("%.2lf ", vector[i]);

        printf("]\n");

        free(vector);
    } else {
        MPI_Gather(local_vector, local_n, MPI_DOUBLE, vector, local_n, MPI_DOUBLE, 0, comm);
    }
}

void multiply(double local_a[], double local_b[], double local_c[], double* local_sum, int local_n) {
    for (int local_i = 0; local_i < local_n; local_i++) {
        local_c[local_i] = local_a[local_i] * local_b[local_i];
        *local_sum += local_c[local_i];
    }
}

void print_sum(double local_sum, double global_sum, int my_rank, MPI_Comm comm) {
    MPI_Reduce(&local_sum, &global_sum, 1, MPI_DOUBLE, MPI_SUM, 0, comm);

    if (my_rank == 0) {
        printf("Skalarni proizvod vektora je %lf\n", global_sum);
    }
}