.\" $Id: pvm_addhosts.3,v 1.1 1996/09/23 22:00:57 pvmsrc Exp $
.TH ADDHOSTS 3PVM "22 February, 1994" "" "PVM Version 3.4"
.SH NAME
pvm_addhosts \- Add hosts to the virtual machine.
.SH SYNOPSIS
.nf
.ft B
C	int info = pvm_addhosts( char **hosts, int nhost, int *infos )
.br

Fortran	call pvmfaddhost( host, info )
.fi

.SH PARAMETERS
.IP hosts 0.8i
An array of strings
naming the hosts to be added.
Pvmd must already be installed and
the user must have an account on the specified hosts.
.br
.IP nhost
Integer specifying the length of array hosts.
.br
.IP infos
Integer array of length
.I nhost
which returns the
status for each host.
Values less than zero indicate an error,
while positive values are TIDs of the new hosts.
.br
.IP host
Character string naming the host to be added.
.br
.IP info
Integer status code returned by the routine.
Values less than \fInhost\fR indicate partial failure,
and
values less than 1 indicate total failure.

.SH DESCRIPTION
The routine
.I pvm_addhosts
adds the computers named in
.I hosts
to the configuration of computers making up the virtual machine.
The names should have the same syntax as lines of a pvmd hostfile
(see man page for pvmd3):
A hostname followed by options of the form xx=y.
.PP
If pvm_addhosts is successful,
.I info
will be equal to
.I nhost.
Partial success is indicated by 0 < info < nhost,
and total failure by info < 1.
The array
.I infos
can be checked to determine which host caused the error.
.PP
The Fortran routine
.I pvmfaddhost
adds a single host to the configuration with each call.
.I info
will be 1 if successful or < 0 if error.
.PP
.\"If a host fails, the PVM system will continue to function.
.\"The user can use this routine to increase the fault tolerance
.\"of his PVM application.
The status of hosts can be requested by the application using
\fIpvm_mstat\fR and \fIpvm_config\fR.
If a host fails it will be automatically deleted from the configuration.
Using pvm_addhosts a replacement host can be added by the application,
however
it is the responsibility of the
application developer to make his application tolerant of host failure.
Another use of this feature would be to add more hosts
as they become available, for example on a weekend, or if the
application dynamically determines it could use more computational power.
.\".PP
.\"pvm_addhosts requires the synchronization of the entire virtual machine.

.SH EXAMPLES
.nf
C:
	static char *hosts[] = {
	    "sparky",
	    "thud.cs.utk.edu",
	};
	info = pvm_addhosts( hosts, 2, infos );
.sp
Fortran:
	CALL PVMFADDHOST( 'azure', INFO )
.fi

.SH ERRORS
The following error conditions can be returned by \fIpvm_addhosts\fR:
.IP PvmBadParam
giving an invalid argument value.
.IP PvmAlready
another task is currently adding hosts.
.IP PvmSysErr
local pvmd is not responding.
.PP

and in the \fIinfos\fR vector:
.IP PvmBadParam
bad hostname syntax.
.IP PvmNoHost
no such host.
.IP PvmCantStart
failed to start pvmd on host.
.IP PvmDupHost
host already configured.
.IP PvmBadVersion
pvmd protocol versions don't match.
.IP PvmOutOfRes
PVM has run out of system resources.
.PP
.SH SEE ALSO
pvm_pvmd3(1PVM),
pvm_delhosts(3PVM),
pvm_start_pvmd(3PVM),
pvm_config(3PVM),
pvm_mstat(3PVM)