Schema_Comm.h

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#ifndef Schema_Comm_included
#define Schema_Comm_included
 
#include <TRUSTArray.h>
#include <TRUST_Ref.h>
 
class Comm_Group;
 
// These objects store a communication graph between
// processors: each proc. has a list of processors to send to
// and a list of processors to receive from.
//
// The group is the set of processors on which it is GUARANTEED
// that the following methods will be called SIMULTANEOUSLY on all
// processors in the group:
// - begin_comm()
// - set_send_recv_pe_list(...)
// - echange_taille_et_messages()
// - end_comm()
//
// In particular: it is forbidden to use these methods inside
// a loop that is not executed the same number of times by all
// processors in the group, nor inside an "if() { }" whose
// execution is not identical on all processors in the group.
//
// It is forbidden to start a new communication while another is
// in progress (a communication always ends with "end_comm()")
// In particular, it is forbidden to use "envoyer", "recevoir" and
// shared disk files between the first call to schema.send_buffer()
// and "terminer()". Be very careful about all methods used between
// these two calls!
//
// On a given PE, an exchange sequence must be built as follows:
// schema.begin_comm()
// schema.send_buffer(pe1) << data_to_send;
// schema.send_buffer(pe2) << data_to_send;
// ...
// schema.echanger_taille_et_messages();
// schema.recv_buffer(pe2) >> data_to_recv;
// schema.recv_buffer(pe3) >> data_to_recv;
// ...
// schema.end_comm();
//
// Communication is not necessarily symmetric: a processor can send
// a message to one processor and receive from another.
// However, the user guarantees that the processor lists provided in
//  send_pe_list and recv_pe_list satisfy the principle "you listen when I speak!"
//  (i.e., processor A belongs to send_pe_list on processor B
//   if and only if processor B belongs to recv_pe_list on processor A).
 
// Modif BM 20/06/2013: adding set_all_to_allv_flag. If the flag is set, the communication
//  scheme uses MPI_alltoallv instead of ISend IRecv. To try to solve
//  problems encountered on supermuc in the file read/write routine
//  (schema where everyone writes to processor 0 => error allocating MPI_requests).
 
class OutputCommBuffer;
class InOutCommBuffers;
class InputCommBuffer;
class Comm_Group;
class Entree;
class Sortie;
 
class Schema_Comm
{
public:
  Schema_Comm();
  Schema_Comm(const Schema_Comm&);
  ~Schema_Comm();
 
  void set_group(const Comm_Group& group);  // Obsolete
  const Comm_Group& get_group() const;
 
  const Schema_Comm& operator= (const Schema_Comm&);
  void set_send_recv_pe_list(const ArrOfInt& send_pe_list, const ArrOfInt& recv_pe_list, const int me_to_me = 0);
 
  void begin_comm() const;                 // Status transitions to WRITING
  // Allowed when status_ == WRITING:
  Sortie& send_buffer(int num_PE) const;
  void echange_taille_et_messages() const; // Status transitions to EXCHANGED
  void echange_messages(const ArrOfInt& recv_size) const;  // Status transitions to EXCHANGED
  // Allowed when status_ == EXCHANGED:
  Entree& recv_buffer(int num_PE) const;
  void end_comm() const;                   // Status transitions to RESET
  // Accessors:
  const ArrOfInt& get_send_pe_list() const;
  const ArrOfInt& get_recv_pe_list() const;
 
  void set_all_to_allv_flag(int x) { use_all_to_allv_ = x; }
 
protected:
  void echange_taille(const ArrOfInt& send_size, ArrOfInt& recv_size) const;
  void echange_messages(const ArrOfInt& send_size, const ArrOfInt& recv_size) const;
  // Status transitions to EXCHANGED
  void check_send_recv_pe_list() const;
 
  // A single status for all exchanges: concurrent access to the class is not supported
  // because we want to limit the number of buffers and the number of "outstanding requests".
  // Therefore: it is forbidden to start a new communication if the buffers
  // are currently in use.
  enum Static_Status { UNINITIALIZED, RESET, WRITING, EXCHANGED };
  static Static_Status status_;
  static OutputCommBuffer& obuffer(int pe);
  static InputCommBuffer&   ebuffer(int pe);
 
  ArrOfInt send_pe_list_; // List of processors to send to
  ArrOfInt recv_pe_list_; // List of processors to receive from
  int   me_to_me_;     // Flag: is sending messages to oneself allowed?
  OBS_PTR(Comm_Group) ref_group_;// Group of processors that will communicate
 
  int use_all_to_allv_; // Flag, which type of communication should be used?
private:
  // Pointers are stored in a specific class (destructor of static members
  // called automatically at end of execution to free memory).
  static InOutCommBuffers buffers_;
  static int n_buffers_;
};
 
class Schema_Comm_statique : public Schema_Comm
{
public:
  //void echange_taille();
  //void echange_messages() const;           // Statut passe a EXCHANGED
  const ArrOfInt& get_send_size() const;
  const ArrOfInt& get_recv_size() const;
protected:
  ArrOfInt send_size_;    // Size of messages to send in bytes
  ArrOfInt recv_size_;    // Size of messages to receive in bytes
};
 
#endif