layout.cpp

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#include "layout.h"

static const char rcsid[] = "$Id: layout.cpp 942 2013-07-22 06:50:06Z aoym $";

// prototype declaration
namespace {
  static int pe_logical_layout(const int ndim, const int *dims, int nproc, int *npe);
  static int find_primes(const int n, int *p);
}

// static members
int Communicator_impl::Layout::m_ndim  = 0;
int *Communicator_impl::Layout::m_dims = 0;  //< lattice extent

// logical layout
int *Communicator_impl::Layout::m_grid_dims  = 0;
int *Communicator_impl::Layout::m_grid_coord = 0;

int *Communicator_impl::Layout::m_ipe_up = 0;
int *Communicator_impl::Layout::m_ipe_dn = 0;

// physical mapping
char Communicator_impl::Layout::m_map_grid[16];
int  *Communicator_impl::Layout::m_physical_to_logical = 0; //< map between physical and logical grid

// subdimensional-slices
MPI_Comm *Communicator_impl::Layout::m_sub_comm = 0;


// communicator_impl methods

int Communicator_impl::Layout::ipe(const int idir)
{
  return m_grid_coord[idir];
}


int Communicator_impl::Layout::npe(const int idir)
{
  return m_grid_dims[idir];
}


int Communicator_impl::Layout::grid_dims(int *dims)
{
  for (int i = 0; i < m_ndim; ++i) {
    dims[i] = m_grid_dims[i];
  }
  return EXIT_SUCCESS;
}


// tag() : identify transfer channel by source rank and direction (incl fw/bw)
int Communicator_impl::Layout::tag(int rank, int idir, int ipm)
{
  return 2 * m_ndim * rank + idir + ((ipm > 0) ? 0 : m_ndim);
}



int Communicator_impl::Layout::layout_setup()
{
  m_ndim = CommonParameters::Ndim();

  // lattice size
  m_dims = new int [m_ndim];

  m_dims[0] = CommonParameters::Lx();
  m_dims[1] = CommonParameters::Ly();
  m_dims[2] = CommonParameters::Lz();
  m_dims[3] = CommonParameters::Lt();

  // suggested logical layout
  m_grid_dims = new int [m_ndim];

  m_grid_dims[0] = CommonParameters::NPEx();
  m_grid_dims[1] = CommonParameters::NPEy();
  m_grid_dims[2] = CommonParameters::NPEz();
  m_grid_dims[3] = CommonParameters::NPEt();

  // suggested local volume
  int *local_dims = new int [m_ndim];

  local_dims[0] = CommonParameters::Nx();
  local_dims[1] = CommonParameters::Ny();
  local_dims[2] = CommonParameters::Nz();
  local_dims[3] = CommonParameters::Nt();

  for (int i = 0; i < m_ndim; ++i) {
    if (local_dims[i] != 0) {  // there is a suggestion of local extent.
      if (m_grid_dims[i] != 0) {
        if (m_grid_dims[i] * local_dims[i] != m_dims[i]) {
          fprintf(stderr, "layout mismatch.\n");
          abort();
        } else {
          // ok. m_grid_dims[i] is as specified.
        }
      } else {  // use specified local size and find number of divisions.
        if (m_dims[i] % local_dims[i] != 0) {
          fprintf(stderr, "layout mismatch. lattice undivisable by local volume.\n");
          abort();
        } else {
          m_grid_dims[i] = m_dims[i] / local_dims[i];
        }
      }
    }
  }

  // find logical layout
  int retv = pe_logical_layout(m_ndim, m_dims, m_grid_size, m_grid_dims);

  if (retv != EXIT_SUCCESS) {
    fprintf(stderr, "layout failed.\n");
    abort();
  }

  // physical to logical map
  physical_map_setup();

  // find logical coordinate of my rank
  m_grid_coord = new int [m_ndim];
  grid_coord(m_grid_coord, m_grid_rank);

  // find neighbour rank
  m_ipe_up = new int [m_ndim];
  m_ipe_dn = new int [m_ndim];

  int *coord = new int [m_ndim];
  for (int i = 0; i < m_ndim; ++i) {
    for (int j = 0; j < m_ndim; ++j) {
      coord[j] = m_grid_coord[j];
    }

    // upward
    coord[i] = (m_grid_coord[i] + 1) % m_grid_dims[i];
    grid_rank(&m_ipe_up[i], coord);

    // downward
    coord[i] = (m_grid_coord[i] - 1 + m_grid_dims[i]) % m_grid_dims[i];
    grid_rank(&m_ipe_dn[i], coord);
  }
  delete [] coord;


#ifdef DEBUG
  printf("rank %d: up=(%d,%d,%d,%d), dn=(%d,%d,%d,%d)\n",
         Communicator::self(),
         m_ipe_up[0], m_ipe_up[1], m_ipe_up[2], m_ipe_up[3],
         m_ipe_dn[0], m_ipe_dn[1], m_ipe_dn[2], m_ipe_dn[3]);
#endif


  // subgrid of reduced dimension.
  subgrid_setup();

  return EXIT_SUCCESS;
}


int Communicator_impl::Layout::layout_delete()
{
  subgrid_delete();

  physical_map_delete();

  delete [] m_dims;
  delete [] m_grid_dims;
  delete [] m_grid_coord;
  delete [] m_ipe_up;
  delete [] m_ipe_dn;

  return EXIT_SUCCESS;
}


// subgrid for communication in reduced dimensional subsets

int Communicator_impl::Layout::subgrid_setup()
{
  m_sub_comm = new MPI_Comm [(1 << m_ndim)];

  for (int imask = 0; imask < (1 << m_ndim); ++imask) {
    int coord[m_ndim];
    for (int i = 0; i < m_ndim; ++i) {
      coord[i] = m_grid_coord[i];
    }

    for (int i = 0; i < m_ndim; ++i) {
      bool mask = ((imask >> i) & 1) == 1 ? true : false;
      if (!mask) coord[i] = 0;
    }

    int rank = 0;
    grid_rank(coord, &rank);

/*
  printf("split %2d: rank %2d: (%d,%d,%d,%d) -> (%d,%d,%d,%d), %2d\n",
  imask,
  m_grid_rank,
  m_grid_coord[0], m_grid_coord[1], m_grid_coord[2], m_grid_coord[3],
  coord[0], coord[1], coord[2], coord[3],
  rank);
*/
    MPI_Comm_split(m_comm, rank, 0 /* key */, &m_sub_comm[imask]);
  }

  return EXIT_SUCCESS;
}


int Communicator_impl::Layout::subgrid_delete()
{
  delete [] m_sub_comm;

  return EXIT_SUCCESS;
}


namespace { // anonymous namespace
// layout
  static const int prime_table[] =
  {
    2,     3,   5,   7,  11,  13,  17,  19,
    23,   29,  31,  37,  41,  43,  47,  53,
    59,   61,  67,  71,  73,  79,  83,  89,
    97,  101, 103, 107, 109, 113, 127, 131,
    137, 139, 149, 151, 157, 163, 167, 173,
    179, 181, 191, 193, 197, 199, 211, 223,
    227, 229, 233, 239, 241, 251, 257, 263,
    269, 271, 277, 281, 283, 293, 307, 311,
  };

  static const int nprime = sizeof(prime_table) / sizeof(int);

//* find logical layout
//*   divide dims_mu into npe_mu x local_mu where prod npe_mu = nproc.
//*   npe_mu != 0 is kept intact.
  static int pe_logical_layout(const int ndim, const int *dims, int nproc, int *npe)
  {
    int retv = EXIT_SUCCESS;

    int nfreedim  = 0;
    int nfreeproc = nproc;

    for (int i = 0; i < ndim; ++i) {
      if (npe[i] == 0) {
        ++nfreedim;
      } else {
        if (npe[i] < 0) {
          fprintf(stderr, "illegal value: npe[%d]=%d.\n", i, npe[i]);
          return EXIT_FAILURE;
        } else if (nproc % npe[i] != 0) {
          fprintf(stderr, "illegal value: npe[%d]=%d does not divide NPE=%d.\n", i, npe[i], nproc);
          return EXIT_FAILURE;
        } else if (nfreeproc % npe[i] != 0) {
          fprintf(stderr, "illegal value: NPE=%d is not divisable by %d.\n", nproc, nproc / nfreeproc * npe[i]);
          return EXIT_FAILURE;
        } else if (dims[i] % npe[i] != 0) {
          fprintf(stderr, "illegal value: npe[%d]=%d does not divide L=%d.\n", i, npe[i], dims[i]);
          return EXIT_FAILURE;
        } else {
          nfreeproc /= npe[i];
        }
      }
    }

    if (nfreeproc < 1) {
      fprintf(stderr, "impossible layout.\n");
      return EXIT_FAILURE;
    } else if (nfreeproc == 1) {
      for (int i = 0; i < ndim; ++i) {
        if (npe[i] == 0) npe[i] = 1;
      }
      return EXIT_SUCCESS;  // complete.
    } else {
      if (nfreedim == 0) {
        fprintf(stderr, "impossible layout. no room to divide.\n");
        return EXIT_FAILURE;
      }
    }

    // divide nfreeproc to nfreedim npe's.
    int np = nfreeproc;

    int *subdims = new int [ndim];
    int nf       = 0;
    for (int i = 0; i < ndim; ++i) {
      if (npe[i] == 0) subdims[nf++] = dims[i]; }

    int *count = new int [nprime];
    for (int i = 0; i < nprime; ++i) {
      count[i] = 0;
    }

    for (int i = 0; i < nprime; ++i) {
      int p = prime_table[i];
      while (np > 1 && np % p == 0)
      {
        ++count[i];
        np /= p;
      }
      if (np == 1) break;
    }

//   printf("%d = (", nfreeproc);
//   for (int i=0; i<nprime; ++i) {
//     printf("%d, ", count[i]);
//   }
//   printf(")\n");

    if (np > 1) {
      fprintf(stderr, "insufficient prime table.\n");
      retv = EXIT_FAILURE;
      goto finalize;
    }

//   printf("subdims=(");
//   for (int i=0; i<nf; ++i) {
//     printf("%d, ", subdims[i]);
//   }
//   printf(")\n");

    for (int i = nprime - 1; i >= 0; --i) {
      if (count[i] == 0) continue;

      int p = prime_table[i];

      for (int j = 0; j < count[i]; ++j) {
        int maxsubdim = 0;
        int maxk      = -1;
        for (int k = 0; k < nf; ++k) {
          if ((subdims[k] >= maxsubdim) && (subdims[k] % p == 0)) {
            maxsubdim = subdims[k];
            maxk      = k;
          }
        }
//      printf("prime=%d, maxk=%d, maxsubdim=%d\n", p, maxk, maxsubdim);

        if (maxk == -1) {
          fprintf(stderr, "not divisable. %d\n", p);
          retv = EXIT_FAILURE;
          goto finalize;
        }

        subdims[maxk] /= p;
      }
    }

/*
  printf("subdims=(");
  for (int i=0; i<nf; ++i) {
  printf("%d, ", subdims[i]);
  }
  printf(")\n");
*/
    // store
    for (int i = 0, k = 0; i < ndim; ++i) {
      if (npe[i] == 0) {
        npe[i] = dims[i] / subdims[k];
        ++k;
      }
    }

finalize:
    delete [] subdims;
    delete [] count;

    return retv;
  }


//* find n primes.
  static int find_primes(const int n, int *p)
  {
    if (n < 1) return EXIT_FAILURE;

    int i = 0;
    int k = 2;

    p[i++] = k++;

    while (1)
    {
      int j;
      for (j = 0; j < i; ++j) {
        if (k % p[j] == 0) break;
      }

      if (j >= i) {  // not divisable by p[0]..p[i-1]. found new prime.
        p[i++] = k;
        if (i >= n) return EXIT_FAILURE;
      }

      ++k;
    }

    return EXIT_SUCCESS;
  }
} // anonymous namespace