---
name: "pvmfnrecv"
section: "3"
platform: "linux"
package: "pvm-dev"
version: "3.4.2-8"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/pvm_nrecv"
---

# pvmfnrecv(3)

Non-blocking receive.

Part of [pvm\_nrecv(3)](/pvm_nrecv/3.md).

## NAME

pvm\_nrecv - Non-blocking receive.

## SYNOPSIS

```
C	int bufid = pvm_nrecv( int tid, int msgtag )
Fortran	call pvmfnrecv( tid, msgtag, bufid )
```

## PARAMETERS

- tid

  **Integer task identifier of sending process supplied by the user.**\

- msgtag

  **Integer message tag supplied by the user.** **msgtag should be \>= 0.**\

- bufid

  **Integer returning the value of the new active receive buffer** **identifier.  Values less than zero indicate an error.**

## DESCRIPTION

**The routine** *pvm\_nrecv* **checks to see if a message with** **label** *msgtag* **has arrived from** *tid.* **and also clears the current receive buffer if any,** **If a matching message has arrived pvm\_nrecv immediately** **places the message in a new** *active* receive buffer, and returns the buffer identifier in *bufid.*

If the requested message has not arrived, then pvm\_nrecv immediately returns with a 0 in *bufid.* If some error occurs *bufid* will be \< 0.

A -1 in *msgtag* or *tid* matches anything. This allows the user the following options. If tid = -1 and msgtag is defined by the user, then pvm\_nrecv will accept a message from any process which has a matching msgtag. If msgtag = -1 and tid is defined by the user, then pvm\_nrecv will accept any message that is sent from process tid. If tid = -1 and msgtag = -1, then pvm\_nrecv will accept any message from any process.

The PVM model guarantees the following about message order. If task 1 sends message A to task 2, then task 1 sends message B to task 2, message A will arrive at task 2 before message B. Moreover, if both messages arrive before task 2 does a receive, then a wildcard receive will always return message A.

pvm\_nrecv is non-blocking in the sense that the routine always returns immediately either with the message or with the information that the message has not arrived at the local pvmd yet. pvm\_nrecv can be called multiple times to check if a given message has arrived yet. In addition the blocking receive pvm\_recv can be called for the same message if the application runs out of work it could do before the data arrives.

If pvm\_nrecv returns with the message, then the data in the message can be unpacked into the user's memory using the unpack routines.

## EXAMPLES

```
C:
	tid = pvm_parent();
	msgtag = 4 ;
	arrived = pvm_nrecv( tid, msgtag );
	if ( arrived > 0)
		info = pvm_upkint( tid_array, 10, 1 );
	else
		/* go do other computing */

Fortran:
	CALL PVMFNRECV( -1, 4, ARRIVED )
	IF ( ARRIVED .gt. 0 ) THEN
	   CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
	   CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
	ELSE
*	   GO DO USEFUL WORK
	ENDIF
```

## ERRORS

These error conditions can be returned by *pvm\_nrecv.*

- PvmBadParam

  giving an invalid tid value or msgtag.

- PvmSysErr

  pvmd not responding.

## SEE ALSO

pvm\_bufinfo(3PVM), pvm\_getminfo(3PVM), pvm\_recv(3PVM), pvm\_unpack(3PVM), pvm\_send(3PVM), pvm\_mcast(3PVM)