.\" $Id: pvm_psend.3,v 1.1 1996/09/23 22:05:55 pvmsrc Exp $
.TH PSEND 3PVM "15 March, 1994" "" "PVM Version 3.4"
.SH NAME
pvm_psend \- Pack and send data in one call.

.SH SYNOPSIS
.nf
.ft B
C	int info = pvm_psend( int tid, int msgtag, char *buf,
.br
	                      int len, int datatype )
.br

Fortran	call pvmfpsend( tid, msgtag, buf, len, datatype,
.br
                        info )
.fi

.SH PARAMETERS
.IP tid 0.8i
Integer task identifier of destination process.
.br
.IP msgtag
Integer message tag supplied by the user.
msgtag should be >= 0.
.br
.IP buf
Pointer to a buffer to send.
.br
.IP len
Length of buffer (in multiple of data type size).
.br
.IP datatype
Type of data to which buf points (see below).
.br
.IP info
Integer status code returned by the routine.

.SH DESCRIPTION
The routine
.I pvm_psend
takes a pointer to a buffer
.I buf
its length
.I len
and its data type
.I datatype
and
sends this data directly to the PVM task identified by
.I tid.
.I msgtag
is used to label the content of the message.
If pvm_psend is successful,
.I info
will be 0. If some error occurs then
.I info
will be < 0.
.PP
pvm_psend data can be received by pvm_precv, pvm_recv, pvm_trecv, or pvm_nrecv.
.PP
The pvm_psend routine is asynchronous.
Computation on the sending processor resumes as soon as the buffer 
is safe for reuse.
This is in
contrast to synchronous communication, during which computation on
the sending processor halts until the matching receive is
executed by the receiving processor.
.PP
In C the \fIdatatype\fR parameter must be one of the following,
depending on the type of data to be sent:
[Version 3.3.0 - This parameter only determines message length,
not data conversion.  It only sends raw bytes]
.ta 4 16
.nf
	\fIdatatype\fR	Data Type
	PVM_STR	string
	PVM_BYTE	byte
	PVM_SHORT	short
	PVM_INT	int
	PVM_FLOAT	real
	PVM_CPLX	complex
	PVM_DOUBLE	double
	PVM_DCPLX	double complex
	PVM_LONG	long integer
	PVM_USHORT	unsigned short int
	PVM_UINT	unsigned int
	PVM_ULONG	unsigned long int
.fi

In Fortran the same data types specified for pack should be used.
.PP
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.
.PP
pvm_psend does not affect the state of the current outgoing message buffer
(created by pvm_initsend and used by pvm_send).
.SH WARNINGS
In some versions of PVM (CM5, I860 and PGON),
messages sent using pvm_psend must be received only by pvm_precv,
likewise those sent with pvm_send
must be received by pvm_recv, pvm_nrecv or pvm_trecv.
pvm_psend is not compatible with pvm_recv
(nor pvm_send with pvm_precv).
In addition, pvm_probe is not interoperable with pvm_psend.
.PP
This problem occurs
because nonstandard message headers are used for efficiency
in the pvm_psend function.
In the generic Unix version of PVM,
the calls are fully interoperable.
.PP
The message tag space is shared between pvm_send and pvm_psend,
so you must be careful to avoid selecting the wrong message
(for example by using a wildcard to match the message).
.SH EXAMPLES
.nf
C:
	info = pvm_psend( tid, msgtag, array, 1000, PVM_FLOAT );
.sp
Fortran:
	CALL PVMFPSEND( TID, MSGTAG, BUF, CNT, REAL4, INFO )
.fi

.SH ERRORS
These error conditions can be returned by
.I pvm_psend
.IP PvmBadParam
giving an invalid tid, msgtag, or datatype.
.IP PvmSysErr
pvmd not responding.
.PP
.SH SEE ALSO
pvm_precv(3PVM),
pvm_send(3PVM)