path: root/mg2d_mpi_test.c

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>

#include <mpi.h>

#include "mg2d.h"
#include "mg2d_boundary.h"
#include "mg2d_constants.h"

#include "components.h"

#define ARRAY_ELEMS(x) (sizeof(x) / sizeof(*x))
#define MIN(x, y) ((x) > (y) ? (y) : (x))

#define MAXITER 64
#define TOL 5e-15

#define DOMAIN_SIZE 1.0
#define FD_STENCIL 2

static const double pde_coeffs[MG2D_DIFF_COEFF_NB] = {
    [MG2D_DIFF_COEFF_00] = 1.0,
    [MG2D_DIFF_COEFF_10] = 0.9,
    [MG2D_DIFF_COEFF_01] = 1.1,
    [MG2D_DIFF_COEFF_20] = 1.2,
    [MG2D_DIFF_COEFF_02] = 0.8,
    [MG2D_DIFF_COEFF_11] = 0.7,
};

#if 1
static double sol_00(double x, double y)
{
    return sin(M_PI * x) * sin(M_PI * y);
}
static double sol_10(double x, double y)
{
    return M_PI * cos(M_PI * x) * sin(M_PI * y);
}
static double sol_01(double x, double y)
{
    return M_PI * sin(M_PI * x) * cos(M_PI * y);
}
static double sol_20(double x, double y)
{
    return -M_PI * M_PI * sol_00(x, y);
}
static double sol_02(double x, double y)
{
    return -M_PI * M_PI * sol_00(x, y);
}
static double sol_11(double x, double y)
{
    return M_PI * M_PI * cos(M_PI * x) * cos(M_PI * y);
}
#define BC_TYPE MG2D_BC_TYPE_FIXVAL
#else
static double sol_00(double x, double y)
{
    return cos(M_PI * x) * cos(M_PI * y);
}
static double sol_10(double x, double y)
{
    return -M_PI * sin(M_PI * x) * cos(M_PI * y);
}
static double sol_01(double x, double y)
{
    return -M_PI * cos(M_PI * x) * sin(M_PI * y);
}
static double sol_20(double x, double y)
{
    return -M_PI * M_PI * sol_00(x, y);
}
static double sol_02(double x, double y)
{
    return -M_PI * M_PI * sol_00(x, y);
}
static double sol_11(double x, double y)
{
    return M_PI * M_PI * sin(M_PI * x) * sin(M_PI * y);
}
#define BC_TYPE MG2D_BC_TYPE_REFLECT
#endif

static double (*sol[MG2D_DIFF_COEFF_NB])(double x, double y) = {
    [MG2D_DIFF_COEFF_00] = sol_00,
    [MG2D_DIFF_COEFF_10] = sol_10,
    [MG2D_DIFF_COEFF_01] = sol_01,
    [MG2D_DIFF_COEFF_20] = sol_20,
    [MG2D_DIFF_COEFF_02] = sol_02,
    [MG2D_DIFF_COEFF_11] = sol_11,
};

int main(int argc, char **argv)
{
    MG2DContext *ctx = NULL;
    long int gridsize;
    int ret = 0;

    DomainGeometry *dg = NULL;
    DomainComponent *dc = NULL;

    size_t patch_start, patch_end, patch_size_y;

    char processor_name[MPI_MAX_PROCESSOR_NAME];
    int nb_processes, rank, processor_name_len;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <N>\n", argv[0]);
        return 1;
    }
    gridsize = strtol(argv[1], NULL, 0);
    if (gridsize <= 0) {
        fprintf(stderr, "Invalid parameters: %ld\n", gridsize);
        return 1;
    }

    MPI_Init(NULL, NULL);

    MPI_Comm_size(MPI_COMM_WORLD, &nb_processes);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Get_processor_name(processor_name, &processor_name_len);

    fprintf(stderr, "This is process %d out of %d, running on %s\n",
            rank, nb_processes, processor_name);

    dg = mg2di_dg_alloc(nb_processes);
    if (!dg) {
        fprintf(stderr, "Error allocating domain geometry\n");
        ret = 1;
        goto fail;
    }

    dg->domain_size[0] = gridsize;
    dg->domain_size[1] = gridsize;

    for (unsigned int i = 0; i < dg->nb_components; i++) {
        size_t patch_start, patch_end, patch_size_y;

        patch_size_y = (gridsize + nb_processes - 1) / nb_processes;
        patch_start  = i * patch_size_y;
        patch_end    = MIN((i + 1) * patch_size_y, gridsize);
        patch_size_y = patch_end - patch_start;
        if (patch_size_y <= 0) {
            fprintf(stderr, "Too many processes for grid size %ld: %d\n", gridsize, nb_processes);
            ret = 1;
            goto fail;
        }

        dg->components[i].interior.start[0] = 0;
        dg->components[i].interior.start[1] = patch_start;
        dg->components[i].interior.size[0] = gridsize;
        dg->components[i].interior.size[1] = patch_size_y;

        dg->components[i].exterior.start[0] = -FD_STENCIL;
        dg->components[i].exterior.start[1] = i ? patch_start : -FD_STENCIL;
        dg->components[i].exterior.size[0] = gridsize + 2 * FD_STENCIL;
        dg->components[i].exterior.size[1] = patch_size_y + ((i == 0) * FD_STENCIL) + ((i == nb_processes - 1) * FD_STENCIL);

        dg->components[i].bnd_is_outer[MG2D_BOUNDARY_0L] = 1;
        dg->components[i].bnd_is_outer[MG2D_BOUNDARY_0U] = 1;
        dg->components[i].bnd_is_outer[MG2D_BOUNDARY_1L] = i == 0;
        dg->components[i].bnd_is_outer[MG2D_BOUNDARY_1U] = i == nb_processes - 1;
    }
    dc = &dg->components[rank];

    patch_size_y = (gridsize + nb_processes - 1) / nb_processes;
    patch_start  = rank * patch_size_y;
    patch_end    = MIN((rank + 1) * patch_size_y, gridsize);
    patch_size_y = patch_end - patch_start;
    if (patch_size_y <= 0) {
        fprintf(stderr, "Too many processes for grid size %ld: %d\n", gridsize, nb_processes);
        ret = 1;
        goto fail;
    }

    //while (ret == 0)
    //    sleep(1);

    ctx = mg2d_solver_alloc_mpi(MPI_COMM_WORLD, (size_t [2]){dc->interior.start[0], dc->interior.start[1]},
                                dc->interior.size);
    if (!ctx) {
        fprintf(stderr, "Error allocating the solver context\n");
        return 1;
    }

    ctx->step[0] = DOMAIN_SIZE / (gridsize - 1);
    ctx->step[1] = DOMAIN_SIZE / (gridsize - 1);

    ctx->fd_stencil = FD_STENCIL;

    ctx->maxiter = MAXITER;
    ctx->nb_relax_pre  = 2;
    ctx->nb_cycles     = 1;
    ctx->nb_relax_post = 2;
    ctx->tol = TOL / (ctx->step[0] * ctx->step[1]);
    ctx->nb_threads = 1;
    ctx->log_level = MG2D_LOG_INFO;

    for (int bnd_loc = 0; bnd_loc < ARRAY_ELEMS(ctx->boundaries); bnd_loc++) {
        MG2DBoundary *bnd = ctx->boundaries[bnd_loc];
        const int ci      = mg2d_bnd_coord_idx(bnd_loc);
        const int bnd_dir = mg2d_bnd_out_dir(bnd_loc);

        double coord[2];

        if (!dc->bnd_is_outer[bnd_loc])
            continue;

        bnd->type = BC_TYPE;

        memset(bnd->val, 0, dc->interior.size[!ci] * sizeof(*bnd->val));

        if (bnd->type == MG2D_BC_TYPE_FIXVAL) {
            for (int j = 1; j < ctx->fd_stencil; j++) {
                double *dst = bnd->val + j * bnd->val_stride;

                coord[ci] = mg2d_bnd_is_upper(bnd_loc) * DOMAIN_SIZE + bnd_dir * j * ctx->step[ci];

                for (ptrdiff_t k = -j; k < (ptrdiff_t)dc->interior.size[!ci] + j; k++) {
                    coord[!ci] = (k + dc->interior.start[!ci]) * ctx->step[!ci];
                    dst[k] = sol[MG2D_DIFF_COEFF_00](coord[0], coord[1]);
                }
            }
        }
    }

    for (size_t y = 0; y < dc->interior.size[1]; y++) {
        const double y_coord = (y + dc->interior.start[1]) * ctx->step[1];

        memset(ctx->u + y * ctx->u_stride, 0, sizeof(*ctx->u) * dc->interior.size[0]);

        for (size_t x = 0; x < dc->interior.size[0]; x++) {
            const double x_coord = x * ctx->step[0];
            double rhs = 0.0;

            for (int i = 0; i < MG2D_DIFF_COEFF_NB; i++) {
                ctx->diff_coeffs[i]->data[ctx->diff_coeffs[i]->stride * y + x] = pde_coeffs[i];
                rhs += pde_coeffs[i] * sol[i](x_coord, y_coord);
            }

            ctx->rhs[y * ctx->rhs_stride + x] = rhs;
        }
    }

    ret = mg2d_solve(ctx);
    if (ret < 0) {
        fprintf(stderr, "Error solving the equation\n");
        ret = 1;
        goto fail;
    }

    mg2d_print_stats(ctx, NULL);

    {
        double max_err = 0.0;

        for (size_t y = 0; y < dc->interior.size[1]; y++) {
            const double y_coord = (y + dc->interior.start[1]) * ctx->step[1];

            for (size_t x = 0; x < dc->interior.size[0]; x++) {
                const double x_coord = x * ctx->step[0];
                double err = fabs(ctx->u[y * ctx->u_stride + x] - sol[MG2D_DIFF_COEFF_00](x_coord, y_coord));
                if (err > max_err)
                    max_err = err;
            }
        }
        MPI_Reduce(rank ? &max_err : MPI_IN_PLACE, &max_err, 1, MPI_DOUBLE, MPI_MAX, 0, MPI_COMM_WORLD);
        if (rank == 0) {
            fprintf(stderr, "max(|solution - exact|): %g\n", max_err);
            fprintf(stdout, "%ld %g\n", gridsize, max_err);
        }
    }

fail:
    mg2d_solver_free(&ctx);
    mg2di_dg_free(&dg);
    MPI_Finalize();
    return ret;
}