.\" $Id: pvm_reg_tasker.3,v 1.1 1996/09/23 22:06:06 pvmsrc Exp $
.TH REG_TASKER 3PVM "16 March, 1994" "" "PVM Version 3.4"
.SH NAME
pvm_reg_tasker \- Register task as PVM task starter.

.SH SYNOPSIS
.nf
.ft B
C	#include <pvmsdpro.h>

	int cc = pvm_reg_tasker()
.br

Fortran	Not Available
.fi

.SH DESCRIPTION

Registers the calling task as a PVM task starter.
When a tasker is registered with a pvmd,
and the pvmd receives a DM_EXEC message,
instead of fork()ing and exec()ing the task itself,
it passes a message to the tasker,
which does the dirty work and sends a message back to the pvmd.

Note:  If this doesn't make sense,
don't worry about it.
This function is for folks who are writing stuff like debugger servers
and so on.
For a more complete explanation of what's going on here,
you should refer to the PVM source code and/or user guide section
on implementation;
this is only a man page.
That said...

When the pvmd receives a \fIDM_EXEC\fR message (request to exec new
tasks),
it searches \fIepath\fR (the PVM executable search path)
for the file name.
If it finds the file,
it then either attempts to start the processes (using \fIfork()\fR and
\fIexec()\fR)
or, if a tasker has registered,
sends it a \fISM_STTASK\fR message.

The format of the SM_STTASK message is:
.ta 4 26
.nf
	int tid	// of task
	int flags	// as passed to spawn()
	string path	// absolute path of the executable
	int argc	// number of args to process
	string argv[argc]	// args
	int nenv	// number of envars to pass to task
	string env[nenv]	// environment strings
.fi

The tasker must attempt to start the process when it gets one of
these messages.
The tasker doesn't reply to the pvmd if the task is successfully started;
the task will reconnect to the pvmd on its own,
using the cookie in envar \fIPVMEPID\fR to identify itself
to the pvmd.

The tasker must send a \fISM_TASKX\fR message to the pvmd when any
task that it owns (has started) exits,
or if it can't start a particular task.
The format of the SM_TASKX message is:

.nf
	int tid	// of task
	int status	// the Unix exit status (from \fIwait()\fR)
	int u_sec	// user time used by the task, seconds
	int u_usec	// microseconds
	int s_sec	// system time used by the task, seconds
	int s_usec	// microseconds
.fi

The tasker task
must use pvm_setopt(PvmResvTids, 1) to allow sending reserved messages.
Messages should be packed using encoding \fIPvmDataDefault\fR to
ensure they can be unpacked anywhere in the system.

pvm_reg_tasker()
returns PvmOk when successful.

.SH SEE ALSO
pvm_spawn(3PVM),
pvm_tasks(3PVM),