NAME
	  ISENDRECV - Sends a message, posts a receive for a reply,
	  and returns immediately. (Asynchronous send-receive)

     SYNOPSIS
	  INCLUDE 'fnx.h'


	  INTEGER FUNCTION ISENDRECV(type, sbuf, scount, node, ptype,
	  typesel, rbuf, rcount)

	  INTEGER type
	  INTEGER sbuf(*)
	  INTEGER scount
	  INTEGER node
	  INTEGER ptype
	  INTEGER typesel
	  INTEGER rbuf(*)
	  INTEGER rcount

     PARAMETERS
	  type	    Type of the	message	to send. Refer to Appendix A
		    of the Paragon(tm) System Fortran Calls Reference
		    Manual for more information	about message types.

	  sbuf	    Buffer containing the message to send. The buffer
		    may	be of any valid	data type.

	  scount    Number of bytes to send in the sbuf	parameter.

	  node	    Node number	of the message destination (the
		    receiving node). Setting node to -1	sends the mes-
		    sage to all	nodes in the application (except the
		    sending node when ptype is the sender's process
		    type).

	  ptype	    Process type of the	message	destination (the
		    receiving process).

	  typesel   Message type(s) to receive.	Refer to Appendix A of
		    the	Paragon(tm) System Fortran Calls Reference
		    Manual for information on message type selectors.

	  rbuf	    Buffer for storing the reply. The buffer can be of
		    any	valid data type, but should match the data
		    type of the	buffer in the corresponding send
		    operation.

	  rcount    Length (in bytes) of the rbuf parameter.

     DESCRIPTION
	  The isendrecv() function sends a message and immediately
	  posts	a receive for a	reply. The isendrecv() function
	  immediately returns a	message	ID that	you can	use with the
	  msgdone() and	msgwait() system calls to determine when the
	  send-receive completes (that is, the reply arrives). When
	  the reply arrives, the calling process receives the message
	  and stores it	in the rbuf buffer.

	  If the reply is too long for the rbuf	buffer,	the receive
	  completes with no error returned, and	the content of the
	  rbuf buffer is undefined.

	  This is an asynchronous system call. The calling process
	  continues to run while the send-receive operation is occur-
	  ring.	To determine if	the message sent is received, do
	  either of the	following:

	  o Use	the msgwait() subroutine to wait until the receive
	    completes.

	  o Loop until the msgdone() function returns 1, indicating
	    that the receive is	complete.

	  You can use the info...() system calls to get	more informa-
	  tion about a message after it	is received.

	  For synchronous message passing applications,	use the	csen-
	  drecv() function instead of the isendrecv() function.

     RETURN VALUES
	  A message ID (mid) for use in	msgcancel(), msgdone(),	msgig-
	  nore(), msgmerge(), or msgwait() system calls

				      NOTE

	       The number of message IDs is limited. The error message
	       ``Too many requests'' is	returned and your application
	       will stop when no message IDs are available for a
	       requested asynchronous send or receive. Your program
	       should release its message IDs as soon as possible by
	       calling msgcancel(), msgdone(), msgignore(), or
	       msgwait().

     ERRORS
				      NOTE

	       The majority of the Fortran I/O errors that you are
	       likely to receive are described in the ``Runtime	Error
	       Messages'' appendix of the Paragon(tm) System Fortran
	       Compiler	User's Guide. This section describes addi-
	       tional errors that you may receive.

     Too many requests

	  Your application has used all	the available message IDs and
	  no message IDs are available.	Use either the msgcancel(),
	  msgdone(), msgignore(), or msgwait() subprogram with the
	  receive to release message IDs.

     EXAMPLES
	  The following	example	shows how to use the isendrecv() func-
	  tion to do an	asynchronous send and receive:

		  include 'fnx.h'

		  integer	   msgid, inode, ipid
		  real		   lbuf, value
		  double precision sbuf0, rbuf0, sbuf1,	rbuf1

		  sbuf0	= 0.0
		  rbuf0	= 0.0
		  sbuf1	= 0.0
		  rbuf1	= 0.0
		  lbuf	= 0.0
		  value	= 3.14

	    c  Identify	self.

		  iam =	mynode()

	    c  If node 0, then ...

		  if(iam .eq. 0) then
		     print *,'Starting ...'
	    c	 Send message to other node(s) and post	receive	for result.

		     sbuf0 = 0.21381
		     msgid = isendrecv(10,sbuf0,8,-1,mypid(),11,rbuf0,8)

	    c	 Do some processing while waiting for results.

		     lbuf = sqrt(value)
		     write (*, 50) value, lbuf
	    50	     format('The square	root of	',F5.2,	' is ',	F5.2)

	    c	 Wait for result.

		     call msgwait(msgid)

	    c	 Display result.

		     write(*, 100) sbuf0, rbuf0
	    100	     format('Arcsin of ', d15.5, ' is ', d15.5)

	    c  If not node 0, then ...

		  else

	    c	 Receive message.

		     call crecv(10, rbuf1, 8)

	    c	 Get sending node and pid (for returning result).

		     inode = infonode()
		     ipid  = infopid()

	    c	 Get value of result.

		     sbuf1 = dasind(rbuf1)

	    c	 Send result to	calling	node.

		     call csend(11, sbuf1, 8, inode, ipid)

		  endif

		  end


     LIMITATIONS AND WORKAROUNDS
	  For information about	limitations and	workarounds, see the
	  release notes	files in /usr/share/release_notes.

     SEE ALSO
	  cprobe(), crecv(), csend(), csendrecv(), hrecv(), hsend(),
	  hsendrecv(), iprobe(), irecv(), isend(), isendrecv(),
	  msgcancel(), msgdone(), msgignore(), msgmerge(), msgwait()