/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */

#include "mpidimpl.h"

/* FIXME: HOMOGENEOUS SYSTEMS ONLY -- no data conversion is performed */

/* FIXME: The routines MPID_Isend, MPID_Issend, MPID_Irsend are nearly 
   identical. It would be better if these did roughly:

   MPID_Irsend -> always eager send (with ready mode for error detection)
   MPID_Issend -> always rendezvous send
   MPID_Isend  -> chose eager/rendezvous based on a threshold (and consider
   making the threshold configurable at either compile time (for best 
   low-latency performance) or run-time (for application tuning).

   Then the 3 routines share little code, particularly if the eager/rendezvous 
   implementations are in their own routine
   */
/*
 * MPID_Isend()
 */
#undef FUNCNAME
#define FUNCNAME MPID_Isend
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
int MPID_Isend(const void * buf, MPI_Aint count, MPI_Datatype datatype, int rank,
	       int tag, MPID_Comm * comm, int context_offset,
               MPID_Request ** request)
{
    MPIDI_msg_sz_t data_sz;
    int dt_contig;
    MPI_Aint dt_true_lb;
    MPID_Datatype * dt_ptr;
    MPID_Request * sreq;
    MPIDI_VC_t * vc=0;
#if defined(MPID_USE_SEQUENCE_NUMBERS)
    MPID_Seqnum_t seqnum;
#endif    
    int eager_threshold = -1;
    int mpi_errno = MPI_SUCCESS;
    MPIDI_STATE_DECL(MPID_STATE_MPID_ISEND);

    MPIDI_FUNC_ENTER(MPID_STATE_MPID_ISEND);

    MPIU_DBG_MSG_FMT(CH3_OTHER,VERBOSE,(MPIU_DBG_FDEST,
                  "rank=%d, tag=%d, context=%d", 
                  rank, tag, comm->context_id + context_offset));

    /* Check to make sure the communicator hasn't already been revoked */
    if (comm->revoked &&
            MPIR_AGREE_TAG != MPIR_TAG_MASK_ERROR_BITS(tag & ~MPIR_Process.tagged_coll_mask) &&
            MPIR_SHRINK_TAG != MPIR_TAG_MASK_ERROR_BITS(tag & ~MPIR_Process.tagged_coll_mask)) {
        MPIU_DBG_MSG(CH3_OTHER,VERBOSE,"Communicator revoked. MPID_ISEND returning");
        MPIR_ERR_SETANDJUMP(mpi_errno,MPIX_ERR_REVOKED,"**revoked");
    }
    
    if (rank == comm->rank && comm->comm_kind != MPID_INTERCOMM)
    {
	mpi_errno = MPIDI_Isend_self(buf, count, datatype, rank, tag, comm, 
			    context_offset, MPIDI_REQUEST_TYPE_SEND, &sreq);
	goto fn_exit;
    }

    if (rank != MPI_PROC_NULL) {
        MPIDI_Comm_get_vc_set_active(comm, rank, &vc);
#ifdef ENABLE_COMM_OVERRIDES
        /* this needs to come before the sreq is created, since the override
         * function is responsible for creating its own request */
        if (vc->comm_ops && vc->comm_ops->isend)
        {
            mpi_errno = vc->comm_ops->isend( vc, buf, count, datatype, rank, tag, comm, context_offset, &sreq);
            goto fn_exit;
        }
#endif
    }

    MPIDI_Request_create_sreq(sreq, mpi_errno, goto fn_exit);
    MPIDI_Request_set_type(sreq, MPIDI_REQUEST_TYPE_SEND);

    if (rank == MPI_PROC_NULL)
    {
	MPIU_Object_set_ref(sreq, 1);
        MPID_cc_set(&sreq->cc, 0);
	goto fn_exit;
    }

    MPIDI_Datatype_get_info(count, datatype, dt_contig, data_sz, dt_ptr, 
			    dt_true_lb);
    
    if (data_sz == 0)
    {
	MPIDI_CH3_Pkt_t upkt;
	MPIDI_CH3_Pkt_eager_send_t * const eager_pkt = &upkt.eager_send;

	MPIDI_Request_set_msg_type(sreq, MPIDI_REQUEST_EAGER_MSG);
	sreq->dev.OnDataAvail = 0;
	    
	MPIU_DBG_MSG(CH3_OTHER,VERBOSE,"sending zero length message");
	MPIDI_Pkt_init(eager_pkt, MPIDI_CH3_PKT_EAGER_SEND);
	eager_pkt->match.parts.rank = comm->rank;
	eager_pkt->match.parts.tag = tag;
	eager_pkt->match.parts.context_id = comm->context_id + context_offset;
	eager_pkt->sender_req_id = sreq->handle;
	eager_pkt->data_sz = 0;
	
	MPIDI_VC_FAI_send_seqnum(vc, seqnum);
	MPIDI_Pkt_set_seqnum(eager_pkt, seqnum);
	MPIDI_Request_set_seqnum(sreq, seqnum);
	
	MPID_THREAD_CS_ENTER(POBJ, vc->pobj_mutex);
	mpi_errno = MPIDI_CH3_iSend(vc, sreq, eager_pkt, sizeof(*eager_pkt));
	MPID_THREAD_CS_EXIT(POBJ, vc->pobj_mutex);
	/* --BEGIN ERROR HANDLING-- */
	if (mpi_errno != MPI_SUCCESS)
	{
            MPID_Request_release(sreq);
	    sreq = NULL;
            MPIR_ERR_SET(mpi_errno, MPI_ERR_OTHER, "**ch3|eagermsg");
	    goto fn_exit;
	}
	/* --END ERROR HANDLING-- */

	goto fn_exit;
    }

    MPIDI_CH3_GET_EAGER_THRESHOLD(&eager_threshold, comm, vc);

    /* FIXME: flow control: limit number of outstanding eager messages
       containing data and need to be buffered by the receiver */
    if (data_sz + sizeof(MPIDI_CH3_Pkt_eager_send_t) <= eager_threshold)
    {
	if (dt_contig)
	{
	    mpi_errno = MPIDI_CH3_EagerContigIsend( &sreq, 
						    MPIDI_CH3_PKT_EAGER_SEND,
						    (char*)buf + dt_true_lb, 
						    data_sz, rank, tag, 
						    comm, context_offset );
	}
	else
	{
	    mpi_errno = MPIDI_CH3_EagerNoncontigSend( &sreq, 
                                                      MPIDI_CH3_PKT_EAGER_SEND,
                                                      buf, count, datatype,
                                                      data_sz, rank, tag, 
                                                      comm, context_offset );
	    /* If we're not complete, then add a reference to the datatype */
	    if (sreq && sreq->dev.OnDataAvail) {
		sreq->dev.datatype_ptr = dt_ptr;
		MPID_Datatype_add_ref(dt_ptr);
	    }
	}
    }
    else
    {
	/* Note that the sreq was created above */
	MPIDI_Request_set_msg_type( sreq, MPIDI_REQUEST_RNDV_MSG );
	mpi_errno = vc->rndvSend_fn( &sreq, buf, count, datatype, dt_contig,
                                     data_sz, dt_true_lb, rank, tag, comm, 
                                     context_offset );
	/* FIXME: fill temporary IOV or pack temporary buffer after send to 
	   hide some latency.  This requires synchronization
           because the CTS packet could arrive and be processed before the 
	   above iStartmsg completes (depending on the progress
           engine, threads, etc.). */
	
	if (sreq && dt_ptr != NULL)
	{
	    sreq->dev.datatype_ptr = dt_ptr;
	    MPID_Datatype_add_ref(dt_ptr);
	}
    }

  fn_exit:
    *request = sreq;

    MPIU_DBG_STMT(CH3_OTHER,VERBOSE,
    {
	if (sreq != NULL)
	{
	    MPIU_DBG_MSG_P(CH3_OTHER,VERBOSE,"request allocated, handle=0x%08x", sreq->handle);
	}
    }
		  );
    
  fn_fail:
    MPIDI_FUNC_EXIT(MPID_STATE_MPID_ISEND);
    return mpi_errno;
}