Parallel operations

Parallel operations

This is an example of cs_user_extra_operations which performs parallel operations.

Example 1

Sum of an integer counter 'ii', here the number of cells.

  cs_gnum_t g_ii = n_cells;

  cs_parall_sum(1, CS_GNUM_TYPE, &g_ii);

  bft_printf("%s: total number of cells = %ld\n", __func__, (long)g_ii);

Example 2

Maximum of an integer counter 'ii', here the number of cells.

  cs_lnum_t ii = n_cells;

  cs_parall_max(1, CS_LNUM_TYPE, &ii);

  bft_printf("%s: max. number of cells per rank = %d\n", __func__, ii);

Example 3

Sum of a real 'rrr', here the volume.

  cs_real_t rrr = cs_sum(n_cells, cell_vol);

  cs_parall_sum(1, CS_REAL_TYPE, &rrr);

  bft_printf("%s: total domain volume = %14.5e\n", __func__, rrr);

Example 4

Minimum of a real 'rrr', here the volume.

  rrr = 0;
  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    if (rrr < cell_vol[c_id])
      rrr = cell_vol[c_id];
  }

  cs_parall_max(1, CS_REAL_TYPE, &rrr);

  bft_printf("%s: max cell volume = %14.5e\n", __func__, rrr);

Example 5

Maximum of a real 'rrr', here the volume.

  rrr = cs_math_big_r;
  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    if (rrr > cell_vol[c_id])
      rrr = cell_vol[c_id];
  }

  cs_parall_min(1, CS_REAL_TYPE, &rrr);

  bft_printf("%s: min cell volume = %14.5e\n", __func__, rrr);

Example 6

Maximum of a real and associated real values; here the volume and its location (3 coordinates).

  rrr = -1;
  cs_real_t xyz[3] = {0, 0, 0};

  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    if (rrr < cell_vol[c_id]) {
      rrr = cell_vol[c_id];
      for (int i = 0; i < 3; i++)
        xyz[i] = cell_cen[c_id][i];
    }
  }

  cs_parall_max_loc_vals(3, &rrr, xyz);

  bft_printf("%s: Max. volume = %14.5e.\n", __func__, rrr);
  bft_printf("Location(x,y,z) = %14.5e, %14.5e, %14.5e\n",
             xyz[0], xyz[1], xyz[2]);

Example 7

Minimum of a real and associated real values; here the volume and its location (3 coordinates).

  rrr = 1e30;
  xyz[0] = 0;
  xyz[1] = 0;
  xyz[2] = 0;

  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    if (rrr > cell_vol[c_id]) {
      rrr = cell_vol[c_id];
      for (int i = 0; i < 3; i++)
        xyz[i] = cell_cen[c_id][i];
    }
  }

  cs_parall_min_loc_vals(3, &rrr, xyz);

  bft_printf("%s: Min. volume = %14.5e.\n ", __func__, rrr);
  bft_printf("           Location (x,y,z) = %14.5e, %14.5e, %14.5e\n",
             xyz[0], xyz[1], xyz[2]);

Example 8

Sum of an array of integers; here, the number of cells, faces, and boundary faces.

local values; note that to avoid counting interior faces on parallel boundaries twice, we check if 'ifacel(1,ifac) .le. ncel', as on a parallel boundary, this is always true for one domain and false for the other.

  cs_gnum_t g_itab[3] = {n_cells, 0, n_b_faces};

  for (cs_lnum_t f_id = 0; f_id < n_i_faces; f_id++)
    if (i_face_cells[f_id][0] <= n_cells)
      g_itab[1]++;

  cs_parall_sum(3, CS_GNUM_TYPE, g_itab);

  bft_printf("%s:\n"
             "Number of cells = %ld\n"
             "Number of interior faces = %ld\n"
             "Number of boundary faces = %ld\n\n",
             __func__, (long)g_itab[0], (long)g_itab[1], (long)g_itab[2]);

Example 9

Maxima from an array of integers; here, the number of cells, faces, and boundary faces.

  cs_lnum_t itab[3];
  itab[0] = n_cells;
  itab[1] = n_i_faces;
  itab[2] = n_b_faces;

  /* global maxima */
  cs_parall_max(3, CS_LNUM_TYPE, itab);

  bft_printf("%s:\n"
             " Max. number of cells per rank = %d\n"
             " Max. number of interior faces per rank = %d\n"
             " Max. number of boundary faces per rank = %d\n\n",
             __func__, (int)itab[0], (int)itab[1], (int)itab[2]);

Example 10

Minima from an array of integers; here, the number of cells, faces, and boundary faces.

  itab[0] = n_cells;
  itab[1] = n_i_faces;
  itab[2] = n_b_faces;

  /* global minima */
  cs_parall_min(3, CS_LNUM_TYPE, itab);

  bft_printf("%s:\n"
             " Min. number of cells per rank = %d\n"
             " Min. number of interior faces per rank = %d\n"
             " Min. number of boundary faces per rank = %d\n\n",
             __func__, (int)itab[0], (int)itab[1], (int)itab[2]);

Example 11

Sum of an array of reals; here, the 3 velocity components (so as to compute a mean for example).

  xyz[0] = 0;
  xyz[1] = 0;
  xyz[2] = 0;

  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    for (cs_lnum_t i = 0; i < 3; i++)
      xyz[i] += cvar_vel[c_id][i];
  }

  /* global sum */
  cs_parall_sum(3, CS_REAL_TYPE, xyz);

  bft_printf("%s:\n"
             " Sum of U on the domain = %14.5e\n"
             " Sum of V on the domain = %14.5e\n"
             " Sum of V on the domain = %14.5e\n\n",
             __func__, xyz[0], xyz[1], xyz[2]);

Example 12

Maximum of an array of reals; here, the 3 velocity components.

  xyz[0] = cvar_vel[0][0];
  xyz[1] = cvar_vel[0][1];
  xyz[2] = cvar_vel[0][2];

  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    for (cs_lnum_t i = 0; i < 3; i++)
      xyz[i] = cs_math_fmax(cvar_vel[c_id][i], xyz[i]);
  }

  /* global maximum */
  cs_parall_max(3, CS_REAL_TYPE, xyz);

  bft_printf("%s:\n"
             " Max. of U on the domain = %14.5e\n"
             " Max. of V on the domain = %14.5e\n"
             " Max. of V on the domain = %14.5e\n\n",
             __func__, xyz[0], xyz[1], xyz[2]);

Example 13

Maximum of an array of reals; here, the 3 velocity components.

  xyz[0] = cvar_vel[0][0];
  xyz[1] = cvar_vel[0][1];
  xyz[2] = cvar_vel[0][2];

  for (cs_lnum_t c_id = 0; c_id < n_cells; c_id++) {
    for (int i = 0; i < 3; i++)
      xyz[i] = cs_math_fmin(cvar_vel[c_id][i], xyz[i]);
  }

  /* global maximum */
  cs_parall_min(3, CS_REAL_TYPE, xyz);

  bft_printf("%s:\n"
             " Min. of U on the domain = %14.5e\n"
             " Min. of V on the domain = %14.5e\n"
             " Min. of V on the domain = %14.5e\n\n",
             __func__, xyz[0], xyz[1], xyz[2]);

Example 14

Broadcast an array of local integers to other ranks; in this example, we use the number of cells, interior faces, and boundary faces from process rank 0 (root_rank).

  int root_rank = 0;
  itab[0] = n_cells;
  itab[1] = n_i_faces;
  itab[2] = n_b_faces;

  /* broadcast from root_rank to all others */
  cs_parall_bcast(root_rank, 3, CS_LNUM_TYPE, itab);

  bft_printf("%s: On rank %d\n"
             "              Number of cells          = %d\n"
             "              Number of interior faces = %d\n"
             "              Number of boundary faces = %d\n\n",
             __func__, root_rank, (int)itab[0], (int)itab[1], (int)itab[2]);

Example 15

Broadcast an array of local reals to other ranks; in this example, we use 3 velocity values from process rank 0 (root_rank).

  xyz[0] = cvar_vel[0][0];
  xyz[1] = cvar_vel[0][1];
  xyz[2] = cvar_vel[0][2];

  /* broadcast from rank irangv to all others */
  cs_parall_bcast(root_rank, 3, CS_REAL_TYPE, xyz);

  bft_printf("%s: On rank %d\n"
             "          Velocity U in first cell = %14.5e\n"
             "          Velocity V in first cell = %14.5e\n"
             "          Velocity W in first cell = %14.5e\n\n",
             __func__, root_rank, xyz[0], xyz[1], xyz[2]);