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Man Pages


Manual Reference Pages  -  PVM_REG_HOSTER (3)

NAME

pvm_reg_hoster - Register task as PVM slave starter.

CONTENTS

Synopsis
Description
See Also

SYNOPSIS


C       #include <pvmsdpro.h>

        int cc = pvm_reg_hoster()

Fortran Not Available

DESCRIPTION

Registers the calling task as a PVM slave pvmd starter. When the master pvmd receives a DM_ADD message, instead of starting the new slave pvmd processes itself, it passes a message to the hoster, which does the dirty work and sends a message back to the pvmd.

Note: This function isn’t for beginners. If you don’t grok what it does, you probably don’t need it. 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 just a man page. That said...

When the master pvmd receives a DM_ADD message (request to add hosts to the virtual machine), it looks up the new host IP addresses, gets parameters from the host file if it was started with one, and sets default parameters. It then either attempts to start the processes (using rsh or rexec()) or, if a hoster has registered, sends it a SM_STHOST message.

The format of the SM_STHOST message is:

    int nhosts                // number of hosts
    {
        int tid               // of host
        string options        // from hostfile so= field
        string login          // in form ‘‘[username@]hostname.domain’’
        string command        // to run on remote host
    } [nhosts]

The hoster should attempt to run each command on each host and record the result. A command usually looks like:
    $PVM_ROOT/lib/pvmd -s -d8 -nhonk 1 80a9ca95:0f5a 4096 3 80a95c43:0000

and a reply from a slave pvmd like:
    ddpro<2312> arch<ALPHA> ip<80a95c43:0b3f> mtu<4096>

When finished, the hoster should send a SM_STHOSTACK message back to the address of the sender (the master pvmd). The format of the reply message is:

    {
        int tid               // of host, must match request
        string status         // result line from slave or error code
    } []                      // implied count

The TIDs in the reply must match those in the request. They may be in a different order, however.

The result string should contain the entire reply (a single line) from each new slave pvmd, or an error code if something went wrong. Legal error codes are the literal names of the pvm_errno codes, for example ‘‘PvmCantStart’’. The default PVM hoster can return PvmDSysErr or PvmCantStart, and the slave pvmd itself can return PvmDupHost.

The hoster must use pvm_setmwid() to set the wait ID in the reply message to the same value as in the request. The wait ID in the request is obtained by calling pvm_getmwid().

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

pvm_reg_hoster() returns PvmOk when successful.

SEE ALSO

pvm_addhosts(3PVM), pvm_config(3PVM), pvm_setmwid(3PVM)
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REG_HOSTER (3PVM) 4 March, 1994

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