request.h

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// The TIMPI Message-Passing Parallelism Library.
// Copyright (C) 2002-2025 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


#ifndef TIMPI_REQUEST_H
#define TIMPI_REQUEST_H

// TIMPI includes
#include "timpi/timpi_config.h"
#include "timpi/status.h"

// C/C++ includes
#ifdef TIMPI_HAVE_MPI
#  include "timpi/ignore_warnings.h"
#  include "mpi.h"
#  include "timpi/restore_warnings.h"
#endif // TIMPI_HAVE_MPI

#include <memory>
#include <vector>
#include <utility>

namespace TIMPI
{

// Forward declarations
struct PostWaitWork;

#ifdef TIMPI_HAVE_MPI

//-------------------------------------------------------------------
typedef MPI_Request request;

#else

// This shouldn't actually be needed, but must be
// a unique type for function overloading to work
// properly.
//
// We'll want some actual data in here, to make it possible for
// waitany() to be used in loops that degrade cleanly.
typedef unsigned int request;
#endif // TIMPI_HAVE_MPI


//-------------------------------------------------------------------
class Request
{
public:
  Request ();

  Request (const request & r);

  Request (const Request & other);

  void cleanup();

  Request & operator = (const Request & other);

  Request & operator = (const request & r);

  ~Request ();

  request * get() { return &_request; }

  const request * get() const { return &_request; }

  Status wait ();

  bool test ();

  bool test (status & status);

  // Breaking non-blocking sends into multiple requests can require
  // chaining multiple requests into a single Request.  After using
  // add_prior_request, any wait() on this request automatically
  // begins with a wait() on a copy of the added Request \p req.
  //
  // The added request should not already have a prior request of its
  // own.  However, if \p this request already has a prior, it will be
  // moved to and thus invoked prior to the new prior request \p req.
  void add_prior_request(const Request & req);

  // Objects of a PostWaitWork subclass can be added to this request,
  // and they will automatically be run() after a wait() on this
  // request completes.  The \p work object must be heap allocated,
  // and will be deleted once \p this Request and any Request copies
  // made from \p this have been cleaned up.
  void add_post_wait_work(PostWaitWork * work);

  static const request null_request;

private:
  request _request;

  std::unique_ptr<Request> _prior_request;

  // post_wait_work->first is a vector of work to do after a wait
  // finishes; post_wait_work->second is a reference count so that
  // Request objects will behave roughly like a shared_ptr and be
  // usable in STL containers
  //
  // FIXME - we require C++11 now, so we can be smarter about this.
  std::pair<std::vector <PostWaitWork * >, unsigned int> * post_wait_work;

  // waitany() takes a container of Requests, so it can't be a member
  // function, but it needs access to each Request's _prior_request
  // and _post_wait_work
  friend std::size_t waitany (std::vector<Request> &);
};

inline Status wait (Request & r) { return r.wait(); }

void wait (std::vector<Request> & r);

std::size_t waitany (std::vector<Request> & r);


} // namespace TIMPI

#endif // TIMPI_REQUEST_H