pvm_reg_tasker(3) Register task as PVM task starter.

SYNOPSIS


C #include <pvmsdpro.h>
int cc = pvm_reg_tasker()
Fortran Not Available

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 DM_EXEC message (request to exec new tasks), it searches epath (the PVM executable search path) for the file name. If it finds the file, it then either attempts to start the processes (using fork() and exec()) or, if a tasker has registered, sends it a SM_STTASK message.

The format of the SM_STTASK message is: 

    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

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 PVMEPID to identify itself to the pvmd.

The tasker must send a SM_TASKX 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: 

    int tid               // of task
    int status            // the Unix exit status (from wait())
    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

The tasker 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_tasker() returns PvmOk when successful.

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