mymalloc.cc

Go to the documentation of this file.

/*******************************************************************************
 * \copyright   This file is part of the GADGET4 N-body/SPH code developed
 * \copyright   by Volker Springel. Copyright (C) 2014-2020 by Volker Springel
 * \copyright   (vspringel@mpa-garching.mpg.de) and all contributing authors.
 *******************************************************************************/
#include "gadgetconfig.h"
 
#include <fcntl.h>
#include <math.h>
#include <mpi.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
 
#include "../data/allvars.h"
#include "../data/dtypes.h"
#include "../data/mymalloc.h"
#include "../logs/logs.h"
#include "../main/simulation.h"
#include "../mpi_utils/mpi_utils.h"
#include "../mpi_utils/shared_mem_handler.h"
#include "../system/system.h"
 
void memory::mymalloc_init(int maxmemsize, enum restart_options restartflag)
{
  BlockSize                    = (size_t *)malloc(MAXBLOCKS * sizeof(size_t));
  Table                        = (char **)malloc(MAXBLOCKS * sizeof(void *));
  MovableFlag                  = (char *)malloc(MAXBLOCKS * sizeof(char));
  GenericFlag                  = (char *)malloc(MAXBLOCKS * sizeof(char));
  BasePointers                 = (char ***)malloc(MAXBLOCKS * sizeof(void **));
  VarName                      = (char *)malloc(MAXBLOCKS * MAXCHARS * sizeof(char));
  FunctionName                 = (char *)malloc(MAXBLOCKS * MAXCHARS * sizeof(char));
  ParentFileName               = (char *)malloc(MAXBLOCKS * MAXCHARS * sizeof(char));
  FileName                     = (char *)malloc(MAXBLOCKS * MAXCHARS * sizeof(char));
  LineNumber                   = (int *)malloc(MAXBLOCKS * sizeof(int));
  HighMarkTabBuf               = (char *)malloc((100 + 4 * MAXCHARS) * (MAXBLOCKS + 10));
  HighMarkTabBufWithoutGeneric = (char *)malloc((100 + 4 * MAXCHARS) * (MAXBLOCKS + 10));
 
  memset(VarName, 0, MAXBLOCKS * MAXCHARS);
  memset(FunctionName, 0, MAXBLOCKS * MAXCHARS);
  memset(ParentFileName, 0, MAXBLOCKS * MAXCHARS);
  memset(FileName, 0, MAXBLOCKS * MAXCHARS);
 
  size_t n = maxmemsize * ((size_t)1024 * 1024);
  n        = roundup_to_multiple_of_cacheline_size(n);
 
  // add an extra cache line size to make sure we can guarantee that base returned from MPI_Win_allocate_shared is aligned
  n += CACHELINESIZE;
 
  RestartFlag = restartflag;
 
  MPI_Barrier(MPI_COMM_WORLD);  // wait until both regular and ghost processors are here
 
  double t0 = Logs.second();
 
  MPI_Info win_info;
  MPI_Info_create(&win_info);
  MPI_Info_set(win_info, "alloc_shared_noncontig", "true");
 
  if(myMPI_Win_allocate_shared(n, 1, win_info, Shmem.SharedMemComm, &Base, &Shmem.SharedMemWin) != MPI_SUCCESS)
    Terminate("Failed to allocate memory for `Base' (%d Mbytes).\n", All.MaxMemSize);
 
  /* we now make sure that the allocated local buffer is really aligned, not all MPI libraries guarantee this */
 
  int off = 0;
  if((long long)Base / CACHELINESIZE > 0)
    off = ((long long)Base / CACHELINESIZE + 1) * CACHELINESIZE - (long long)Base;
 
  /* allign our base */
  Base += off;
 
  MPI_Info_free(&win_info);
 
  double t1 = Logs.second();
  if(Shmem.World_ThisTask == 0)
    mpi_printf("MALLOC: Allocation of shared memory took %g sec\n", Logs.timediff(t0, t1));
 
  TotBytes = FreeBytes = n - CACHELINESIZE;
 
  AllocatedBytes                  = 0;
  Nblocks                         = 0;
  HighMarkBytes                   = 0;
  HighMarkBytesWithoutGeneric     = 0;
  OldGlobHighMarkMB               = 0;
  OldGlobHighMarkMBWithoutGeneric = 0;
 
  char mode[2], buf[MAXLEN_PATH_EXTRA];
 
  if(All.RestartFlag == RST_BEGIN)
    strcpy(mode, "w");
  else
    strcpy(mode, "a");
 
  MPI_Bcast(All.OutputDir, sizeof(All.OutputDir), MPI_BYTE, 0, MPI_COMM_WORLD);
 
  if(Shmem.GhostRank == 0)
    sprintf(buf, "%s%s", All.OutputDir, "memory.txt");
  else
    sprintf(buf, "%s%s", All.OutputDir, "memory_ghostranks.txt");
 
  if(!(FdMemory = fopen(buf, mode)))
    Terminate("error in opening file '%s'\n", buf);
 
  /* tell also the ghost ranks about the total size of the simulation partition */
  MPI_Bcast(&Shmem.Sim_NTask, 1, MPI_INT, 0, MPI_COMM_WORLD);
 
  Shmem.GetGhostRankForSimulCommRank = (int *)mymalloc("GetGhostRankForSimulCommRank", Shmem.Sim_NTask * sizeof(int));
  Shmem.GetShmRankForSimulCommRank   = (int *)mymalloc("GetShmRankForSimulCommRank", Shmem.Sim_NTask * sizeof(int));
  Shmem.GetNodeIDForSimulCommRank    = (int *)mymalloc("GetNodeIDForSimulCommRank", Shmem.Sim_NTask * sizeof(int));
 
  if(Shmem.GhostRank == 0)
    {
      MPI_Allgather(&Shmem.MyShmRankInGlobal, 1, MPI_INT, Shmem.GetGhostRankForSimulCommRank, 1, MPI_INT, Shmem.SimulationComm);
      MPI_Allgather(&Shmem.Island_ThisTask, 1, MPI_INT, Shmem.GetShmRankForSimulCommRank, 1, MPI_INT, Shmem.SimulationComm);
      MPI_Allgather(&Shmem.Island_Smallest_WorldTask, 1, MPI_INT, Shmem.GetNodeIDForSimulCommRank, 1, MPI_INT, Shmem.SimulationComm);
    }
 
  // to make sure that also the ghost processors have this table
  MPI_Bcast(Shmem.GetGhostRankForSimulCommRank, Shmem.Sim_NTask, MPI_INT, 0, MPI_COMM_WORLD);
  MPI_Bcast(Shmem.GetShmRankForSimulCommRank, Shmem.Sim_NTask, MPI_INT, 0, MPI_COMM_WORLD);
 
  /* we also need the base offsets of the other MPI ranks in the same shared memory island */
  Shmem.SharedMemBaseAddr = (void **)mymalloc("SharedMemBaseAddr", Shmem.Island_NTask * sizeof(void *));
 
  for(int i = 0; i < Shmem.Island_NTask; i++)
    {
      MPI_Aint size;
      int disp_unit;
      myMPI_Win_shared_query(Shmem.SharedMemWin, i, &size, &disp_unit, &Shmem.SharedMemBaseAddr[i]);
    }
 
  // now propagte the alignment correction also to the base addresses that all the other processes see
  int *off_list = (int *)Mem.mymalloc("off_list", Shmem.Island_NTask * sizeof(int));
 
  MPI_Allgather(&off, 1, MPI_INT, off_list, 1, MPI_INT, Shmem.SharedMemComm);
 
  for(int i = 0; i < Shmem.Island_NTask; i++)
    Shmem.SharedMemBaseAddr[i] = (char *)Shmem.SharedMemBaseAddr[i] + off_list[i];
 
  Mem.myfree(off_list);
}
 
int memory::myMPI_Win_allocate_shared(MPI_Aint size, int disp_unit, MPI_Info info, MPI_Comm comm, void *baseptr, MPI_Win *win)
{
#ifndef ALLOCATE_SHARED_MEMORY_VIA_POSIX
  return MPI_Win_allocate_shared(size, disp_unit, info, comm, baseptr, win);
#else
 
  char shmpath[NAME_MAX];
 
  /* Base offsets of the other MPI ranks in our shared memory mapping */
  Shmem.SharedMemBaseAddrRaw = (char **)malloc(Shmem.Island_NTask * sizeof(char *));
 
  long long *size_list = (long long *)malloc(Shmem.Island_NTask * sizeof(long long));
 
  long long loc_bytes = size;
  MPI_Allgather(&loc_bytes, 1, MPI_LONG_LONG, size_list, 1, MPI_LONG_LONG, comm);
 
  long long tot_bytes = 0;
  for(int i = 0; i < Shmem.Island_NTask; i++)
    tot_bytes += size_list[i];
 
  if(Shmem.Island_ThisTask == 0)
    {
      sprintf(shmpath, "/G4-%lld.dat", (long long)getpid());
 
      int fd = shm_open(shmpath, O_CREAT | O_EXCL | O_RDWR, S_IRUSR | S_IWUSR);
      if(fd == -1)
        Terminate("shm_open failed in creation");
 
      if(ftruncate(fd, tot_bytes) == -1)
        Terminate("ftruncate failed");
 
      /* Map the object into the caller's address space. */
 
      void *buf = mmap(NULL, tot_bytes, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
      if(buf == MAP_FAILED)
        Terminate("mmap failed");
 
      Shmem.SharedMemBaseAddrRaw[0] = (char *)buf;
    }
 
  MPI_Bcast(shmpath, NAME_MAX, MPI_BYTE, 0, comm);
 
  if(Shmem.Island_ThisTask != 0)
    {
      int fd = shm_open(shmpath, O_RDWR, 0);
      if(fd == -1)
        Terminate("shm open failed in access");
 
      void *buf = mmap(NULL, tot_bytes, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
      if(buf == MAP_FAILED)
        Terminate("mmap failed");
 
      Shmem.SharedMemBaseAddrRaw[0] = (char *)buf;
    }
 
  for(int i = 1; i < Shmem.Island_NTask; i++)
    Shmem.SharedMemBaseAddrRaw[i] = (char *)Shmem.SharedMemBaseAddrRaw[i - 1] + size_list[i - 1];
 
  char **p = (char **)baseptr;
 
  *p = Shmem.SharedMemBaseAddrRaw[Shmem.Island_ThisTask];
 
  free(size_list);
 
  MPI_Barrier(comm);
 
  if(Shmem.Island_ThisTask == 0)
    shm_unlink(shmpath);
 
  return MPI_SUCCESS;
#endif
}
 
int memory::myMPI_Win_shared_query(MPI_Win win, int rank, MPI_Aint *size, int *disp_unit, void *baseptr)
{
#ifndef ALLOCATE_SHARED_MEMORY_VIA_POSIX
  return MPI_Win_shared_query(win, rank, size, disp_unit, baseptr);
#else
 
  char **p = (char **)baseptr;
 
  *p = Shmem.SharedMemBaseAddrRaw[rank];
 
  return MPI_SUCCESS;
#endif
}
 
void memory::report_memory_usage(int rank, char *tabbuf)
{
  int thistask;
  MPI_Comm_rank(Communicator, &thistask);
 
  if(thistask == rank)
    {
      char *buf = (char *)mymalloc("buf", (100 + 4 * MAXCHARS) * (Nblocks + 10));
      int cc    = 0;
      cc += sprintf(buf + cc, "\nMEMORY:  Largest Allocation = %g Mbyte  |  Largest Allocation Without Generic = %g Mbyte\n\n",
                    OldGlobHighMarkMB, OldGlobHighMarkMBWithoutGeneric);
 
      cc += sprintf(buf + cc, "%s", tabbuf);
      if(thistask == 0)
        {
          if(RestartFlag == RST_BEGIN || RestartFlag == RST_RESUME || RestartFlag == RST_STARTFROMSNAP)
            {
              fprintf(FdMemory, "%s", buf);
              fflush(FdMemory);
            }
        }
      else
        {
          MPI_Send(&cc, 1, MPI_INT, 0, TAG_N, Communicator);
          MPI_Send(buf, cc + 1, MPI_BYTE, 0, TAG_PDATA, Communicator);
        }
      myfree(buf);
    }
 
  if(thistask == 0 && rank > 0)
    {
      int cc;
      MPI_Recv(&cc, 1, MPI_INT, rank, TAG_N, Communicator, MPI_STATUS_IGNORE);
      char *buf = (char *)mymalloc("buf", cc + 1);
      MPI_Recv(buf, cc + 1, MPI_BYTE, rank, TAG_PDATA, Communicator, MPI_STATUS_IGNORE);
      if(RestartFlag == RST_BEGIN || RestartFlag == RST_RESUME || RestartFlag == RST_STARTFROMSNAP)
        {
          fprintf(FdMemory, "%s", buf);
          fflush(FdMemory);
        }
      myfree(buf);
    }
}
 
void memory::report_detailed_memory_usage_of_largest_task(void)
{
  int flag = 0;
  int thistask;
  MPI_Comm_rank(Communicator, &thistask);
 
  struct
  {
    double mem;
    int rank;
  } local, global;
 
  local.mem  = HighMarkBytes * TO_MBYTE_FAC;
  local.rank = thistask;
 
  MPI_Allreduce(&local, &global, 1, MPI_DOUBLE_INT, MPI_MAXLOC, Communicator);
 
  if(global.mem >= 1.05 * OldGlobHighMarkMB)
    {
      OldGlobHighMarkMB = global.mem;
      flag |= 1;
    }
 
  local.mem  = HighMarkBytesWithoutGeneric * TO_MBYTE_FAC;
  local.rank = thistask;
 
  MPI_Allreduce(&local, &global, 1, MPI_DOUBLE_INT, MPI_MAXLOC, Communicator);
 
  if(global.mem >= 1.05 * OldGlobHighMarkMBWithoutGeneric)
    {
      OldGlobHighMarkMBWithoutGeneric = global.mem;
      flag |= 2;
    }
 
  if(flag & 2)
    report_memory_usage(global.rank, HighMarkTabBufWithoutGeneric);
 
  if(flag & 1)
    report_memory_usage(global.rank, HighMarkTabBuf);
}
 
void memory::dump_memory_table(void)
{
  char *buf = (char *)malloc(200 * (Nblocks + 10));
  dump_memory_table_buffer(buf);
  printf("%s", buf);
  free(buf);
}
 
int memory::dump_memory_table_buffer(char *p)
{
  int cc              = 0;
  size_t totBlocksize = 0;
  int thistask;
  MPI_Comm_rank(Communicator, &thistask);
 
  cc +=
      sprintf(p + cc, "-------------------------- Allocated Memory Blocks---- ( Step %8d )------------------\n", All.NumCurrentTiStep);
  cc += sprintf(p + cc, "Task    Nr F                  Variable      MBytes   Cumulative  Function|File|Linenumber\n");
  cc += sprintf(p + cc, "------------------------------------------------------------------------------------------\n");
  for(int i = 0; i < Nblocks; i++)
    {
      totBlocksize += BlockSize[i];
 
      cc += sprintf(p + cc, "%4d %5d %d %40s  %10.4f   %10.4f  %s%s()|%s|%d\n", thistask, i, MovableFlag[i], VarName + i * MAXCHARS,
                    BlockSize[i] * TO_MBYTE_FAC, totBlocksize * TO_MBYTE_FAC, ParentFileName + i * MAXCHARS,
                    FunctionName + i * MAXCHARS, FileName + i * MAXCHARS, LineNumber[i]);
    }
  cc += sprintf(p + cc, "------------------------------------------------------------------------------------------\n");
 
  return cc;
}
 
void *memory::mymalloc_movable_fullinfo(void *ptr, const char *varname, size_t n, const char *func, const char *file, int line,
                                        int movable_flag, int clear_flag, char *callorigin)
{
  if((n % CACHELINESIZE) > 0)
    n = (n / CACHELINESIZE + 1) * CACHELINESIZE;
 
  if(n < CACHELINESIZE)
    n = CACHELINESIZE;
 
  if(Nblocks >= MAXBLOCKS)
    Terminate("No blocks left in mymalloc_fullinfo() at %s()/%s/line %d. MAXBLOCKS=%d\n", func, file, line, MAXBLOCKS);
 
  if(n > FreeBytes)
    {
      dump_memory_table();
      Terminate(
          "\nNot enough memory in mymalloc_fullinfo() to allocate %g MB for variable '%s' at %s()/%s/line %d (FreeBytes=%g MB).\n",
          n * TO_MBYTE_FAC, varname, func, file, line, FreeBytes * TO_MBYTE_FAC);
    }
  Table[Nblocks] = Base + (TotBytes - FreeBytes);
  FreeBytes -= n;
 
  strncpy(VarName + Nblocks * MAXCHARS, varname, MAXCHARS - 1);
  if(callorigin)
    {
      strncpy(ParentFileName + Nblocks * MAXCHARS, callorigin, MAXCHARS - 1);
      GenericFlag[Nblocks] = 1;
      AllocatedBytesGeneric += n;
    }
  else
    {
      memset(ParentFileName + Nblocks * MAXCHARS, 0, MAXCHARS);
      GenericFlag[Nblocks] = 0;
    }
  strncpy(FunctionName + Nblocks * MAXCHARS, func, MAXCHARS - 1);
  strncpy(FileName + Nblocks * MAXCHARS, file, MAXCHARS - 1);
  LineNumber[Nblocks] = line;
 
  AllocatedBytes += n;
  BlockSize[Nblocks]    = n;
  MovableFlag[Nblocks]  = movable_flag;
  BasePointers[Nblocks] = (char **)ptr;
 
  Nblocks += 1;
 
  if(AllocatedBytes - AllocatedBytesGeneric > HighMarkBytesWithoutGeneric)
    {
      HighMarkBytesWithoutGeneric = AllocatedBytes - AllocatedBytesGeneric;
      dump_memory_table_buffer(HighMarkTabBufWithoutGeneric);
    }
 
  if(AllocatedBytes > HighMarkBytes)
    {
      HighMarkBytes = AllocatedBytes;
      dump_memory_table_buffer(HighMarkTabBuf);
    }
 
  if(clear_flag)
    memset(Table[Nblocks - 1], 0, n);
 
  return Table[Nblocks - 1];
}
 
size_t memory::roundup_to_multiple_of_cacheline_size(size_t n)
{
  if((n % CACHELINESIZE) > 0)
    n = (n / CACHELINESIZE + 1) * CACHELINESIZE;
 
  return n;
}
 
void *memory::myfree_query_last_block(void)
{
  if(Nblocks == 0)
    Terminate("no allocated blocks that could be returned");
 
  return Table[Nblocks - 1];
}
 
void memory::myfree_movable_fullinfo(void *p, const char *func, const char *file, int line, int movable_flag)
{
  if(Nblocks == 0)
    Terminate("no allocated blocks that could be freed");
 
  /* first, let's find the block */
  int nr;
 
  if(movable_flag)
    {
      for(nr = Nblocks - 1; nr >= 0; nr--)
        if(p == Table[nr])
          break;
 
      if(nr < 0)
        {
          dump_memory_table();
          Terminate("Wrong call of myfree_movable() from %s()/%s/line %d - this block has not been allocated!\n", func, file, line);
        }
 
      if(nr < Nblocks - 1) /* the block is not the last allocated block */
        {
          /* check that all subsequent blocks are actually movable */
          for(int i = nr + 1; i < Nblocks; i++)
            if(MovableFlag[i] == 0)
              {
                dump_memory_table();
                myflush(stdout);
                Terminate(
                    "Wrong call of myfree_movable() from %s()/%s/line %d - behind block=%d there are subsequent non-movable allocated "
                    "blocks\n",
                    func, file, line, nr);
              }
        }
    }
  else
    {
      nr = Nblocks - 1;
      if(p != Table[nr])
        {
          dump_memory_table();
          Terminate("Wrong call of myfree() at %s()/%s/line %d: not the last allocated block!\n", func, file, line);
        }
    }
 
  if(GenericFlag[nr])
    AllocatedBytesGeneric -= BlockSize[nr];
 
  AllocatedBytes -= BlockSize[nr];
  FreeBytes += BlockSize[nr];
 
  if(BasePointers[nr])
    *BasePointers[nr] = NULL;
 
  if(movable_flag)
    {
      ptrdiff_t offset = -BlockSize[nr];
      size_t length    = 0;
 
      for(int i = nr + 1; i < Nblocks; i++)
        length += BlockSize[i];
 
      if(nr < Nblocks - 1)
        memmove(Table[nr + 1] + offset, Table[nr + 1], length);
 
      for(int i = nr + 1; i < Nblocks; i++)
        {
          Table[i] += offset;
          *BasePointers[i] = *BasePointers[i] + offset;
        }
 
      for(int i = nr + 1; i < Nblocks; i++)
        {
          Table[i - 1]        = Table[i];
          BasePointers[i - 1] = BasePointers[i];
          BlockSize[i - 1]    = BlockSize[i];
          MovableFlag[i - 1]  = MovableFlag[i];
          GenericFlag[i - 1]  = GenericFlag[i];
 
          memmove(VarName + (i - 1) * MAXCHARS, VarName + i * MAXCHARS, MAXCHARS);
          memmove(FunctionName + (i - 1) * MAXCHARS, FunctionName + i * MAXCHARS, MAXCHARS);
          memmove(ParentFileName + (i - 1) * MAXCHARS, ParentFileName + i * MAXCHARS, MAXCHARS);
          memmove(FileName + (i - 1) * MAXCHARS, FileName + i * MAXCHARS, MAXCHARS);
          LineNumber[i - 1] = LineNumber[i];
        }
    }
 
  Nblocks -= 1;
}
 
void *memory::myrealloc_movable_fullinfo(void *p, size_t n, const char *func, const char *file, int line, int movable_flag)
{
  if((n % CACHELINESIZE) > 0)
    n = (n / CACHELINESIZE + 1) * CACHELINESIZE;
 
  if(n < CACHELINESIZE)
    n = CACHELINESIZE;
 
  if(Nblocks == 0)
    Terminate("no allocated blocks that could be reallocated");
 
  /* first, let's find the block */
  int nr;
 
  if(movable_flag)
    {
      for(nr = Nblocks - 1; nr >= 0; nr--)
        if(p == Table[nr])
          break;
 
      if(nr < 0)
        {
          dump_memory_table();
          Terminate("Wrong call of myrealloc_movable() from %s()/%s/line %d - this block has not been allocated!\n", func, file, line);
        }
 
      if(nr < Nblocks - 1) /* the block is not the last allocated block */
        {
          /* check that all subsequent blocks are actually movable */
          for(int i = nr + 1; i < Nblocks; i++)
            if(MovableFlag[i] == 0)
              {
                dump_memory_table();
                Terminate(
                    "Wrong call of myrealloc_movable() from %s()/%s/line %d - behind block=%d there are subsequent non-movable "
                    "allocated blocks\n",
                    func, file, line, nr);
              }
        }
    }
  else
    {
      nr = Nblocks - 1;
 
      if(p != Table[nr])
        {
          dump_memory_table();
          Terminate("Wrong call of myrealloc() at %s()/%s/line %d - not the last allocated block!\n", func, file, line);
        }
    }
 
  if(GenericFlag[nr])
    Terminate("unexpected");
 
  AllocatedBytes -= BlockSize[nr];
  FreeBytes += BlockSize[nr];
 
  if(n > FreeBytes)
    {
      dump_memory_table();
      Terminate("At %s()/%s/line %d: Not enough memory in myremalloc_movable(n=%g MB). previous=%g FreeBytes=%g MB\n", func, file,
                line, n * TO_MBYTE_FAC, BlockSize[nr] * TO_MBYTE_FAC, FreeBytes * TO_MBYTE_FAC);
    }
 
  ptrdiff_t offset = n - BlockSize[nr];
  size_t length    = 0;
 
  for(int i = nr + 1; i < Nblocks; i++)
    length += BlockSize[i];
 
  if(nr < Nblocks - 1)
    memmove(Table[nr + 1] + offset, Table[nr + 1], length);
 
  for(int i = nr + 1; i < Nblocks; i++)
    {
      Table[i] += offset;
 
      *BasePointers[i] = *BasePointers[i] + offset;
    }
 
  FreeBytes -= n;
  AllocatedBytes += n;
  BlockSize[nr] = n;
 
  if(AllocatedBytes > HighMarkBytes)
    {
      HighMarkBytes = AllocatedBytes;
      dump_memory_table_buffer(HighMarkTabBuf);
    }
 
  return Table[nr];
}
 
void memory::check_maxmemsize_setting(int maxmemsize)
{
  int errflag = 0, errflag_tot;
 
  if(maxmemsize > (MemoryOnNode / 1024.0 / TasksInThisNode) && RankInThisNode == 0)
    {
      char name[MPI_MAX_PROCESSOR_NAME];
      int len;
      MPI_Get_processor_name(name, &len);
 
      printf("On node '%s', we have %d MPI ranks and at most %g MB available. This is not enough space for MaxMemSize = %g MB\n", name,
             TasksInThisNode, MemoryOnNode / 1024.0, (double)maxmemsize);
      errflag = 1;
      fflush(stdout);
    }
 
  if(maxmemsize > (SharedMemoryOnNode / 1024.0 / TasksInThisNode) && RankInThisNode == 0)
    {
      char name[MPI_MAX_PROCESSOR_NAME];
      int len;
      MPI_Get_processor_name(name, &len);
 
      printf(
          "On node '%s', we have %d MPI ranks and at most %g MB of *shared* memory available. This is not enough space for MaxMemSize "
          "= %g MB\n",
          name, TasksInThisNode, SharedMemoryOnNode / 1024.0, (double)maxmemsize);
      errflag = 1;
      fflush(stdout);
    }
 
  MPI_Allreduce(&errflag, &errflag_tot, 1, MPI_INT, MPI_MAX, Communicator);
 
  if(errflag_tot)
    Terminate("At least one node has insufficient memory");
}