dress-graph/examples/c/mpi_omp_igraph.c at main · velicast/dress-graph · GitHub

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/* mpi_omp_igraph.c — Rook vs Shrikhande with Δ¹-DRESS (MPI + OpenMP, igraph)
 *
 * Same comparison as mpi_igraph.c but using the CUDA + MPI backend.
 * Including dress/mpi/omp/igraph/dress.h redirects dress_delta_fit()
 * to the GPU + MPI implementation — no source changes required.
 *
 * Build & run:
 *   mpicc -O2 -fopenmp -o mpi_cuda_igraph mpi_omp_igraph.c \
 *       -ldress \
 *       $(pkg-config --cflags --libs igraph) -lm
 *   mpirun -np 4 ./mpi_cuda_igraph
 */
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#include <igraph/igraph.h>
/* Order matters: cuda first, then mpi detects it and routes to GPU + MPI. */
#include <dress/mpi/omp/igraph/dress.h>

static int hist_equal(const dress_hist_pair_t *a, const dress_hist_pair_t *b,
                      int hs_a, int hs_b) {
    if (hs_a != hs_b) return 0;
    for (int i = 0; i < hs_a; i++) {
        if (a[i].value != b[i].value || a[i].count != b[i].count) return 0;
    }
    return 1;
}

static igraph_t make_graph(const int *edges, int n_edges) {
    igraph_t g;
    igraph_vector_int_t ev;
    igraph_vector_int_init(&ev, 2 * n_edges);
    for (int i = 0; i < 2 * n_edges; i++)
        VECTOR(ev)[i] = edges[i];
    igraph_create(&g, &ev, 0, IGRAPH_DIRECTED);
    igraph_vector_int_destroy(&ev);
    return g;
}

int main(int argc, char **argv) {
    MPI_Init(&argc, &argv);
    int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    igraph_set_attribute_table(&igraph_cattribute_table);

    /* Rook L₂(4) = K₄ □ K₄ — 16 vertices, 96 directed edges */
    int rook_e[] = {0,1,0,4,0,2,0,8,0,3,0,12,1,5,1,2,1,9,1,3,1,13,2,6,2,10,2,3,2,14,3,7,3,11,3,15,4,5,4,6,4,8,4,7,4,12,5,6,5,9,5,7,5,13,6,10,6,7,6,14,7,11,7,15,8,9,8,10,8,11,8,12,9,10,9,11,9,13,10,11,10,14,11,15,12,13,12,14,12,15,13,14,13,15,14,15,
                    1,0,4,0,2,0,8,0,3,0,12,0,5,1,2,1,9,1,3,1,13,1,6,2,10,2,3,2,14,2,7,3,11,3,15,3,5,4,6,4,8,4,7,4,12,4,6,5,9,5,7,5,13,5,10,6,7,6,14,6,11,7,15,7,9,8,10,8,11,8,12,8,10,9,11,9,13,9,11,10,14,10,15,11,13,12,14,12,15,12,14,13,15,13,15,14};

    /* Shrikhande — 16 vertices, 96 directed edges */
    int shri_e[] = {0,4,0,12,0,1,0,3,0,5,0,15,1,5,1,13,1,2,1,6,1,12,2,6,2,14,2,3,2,7,2,13,3,7,3,15,3,4,3,14,4,8,4,5,4,7,4,9,5,9,5,6,5,10,6,10,6,7,6,11,7,11,7,8,8,12,8,9,8,11,8,13,9,13,9,10,9,14,10,14,10,11,10,15,11,15,11,12,12,13,12,15,13,14,14,15,
                    4,0,12,0,1,0,3,0,5,0,15,0,5,1,13,1,2,1,6,1,12,1,6,2,14,2,3,2,7,2,13,2,7,3,15,3,4,3,14,3,8,4,5,4,7,4,9,4,9,5,6,5,10,5,10,6,7,6,11,6,11,7,8,7,12,8,9,8,11,8,13,8,13,9,10,9,14,9,14,10,11,10,15,10,15,11,12,11,13,12,15,12,14,13,15,14};

    igraph_t rook = make_graph(rook_e, 96);
    igraph_t shri = make_graph(shri_e, 96);

    delta_dress_result_igraph_t dr, ds;
    dress_delta_fit(&rook, NULL, NULL, DRESS_VARIANT_UNDIRECTED,
                    1, 100, 1e-6, 0, 0, 0, 0, 1, &dr);
    dress_delta_fit(&shri, NULL, NULL, DRESS_VARIANT_UNDIRECTED,
                    1, 100, 1e-6, 0, 0, 0, 0, 1, &ds);

    if (rank == 0) {
        printf("Rook:       %d entries\n", dr.hist_size);
        printf("Shrikhande: %d entries\n", ds.hist_size);

        int same = hist_equal(dr.histogram, ds.histogram,
                              dr.hist_size, ds.hist_size);
        printf("Histograms differ: %s\n", same ? "no" : "yes");
    }

    delta_dress_free(&dr);
    delta_dress_free(&ds);
    igraph_destroy(&rook);
    igraph_destroy(&shri);

    MPI_Finalize();
    return 0;
}