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PVM Console

PVM Console

Functions

• PVM console is analagous to a console on any multi-tasking computer. It is used to
  • configure the virtual machine

  • start pvm tasks (including the daemon)

  • stop pvm tasks

  • receives information and error messages

Starting the console

pvm

• The console may be started and stopped multiple times on any of the hosts on which PVM is running

• The console responds with the prompt

• The console accepts commands from standard input

Configuration of PVM

conf

• The configuration of the virtual machine may be listed using the conf command

1 host, 1 data format

HOST DTID ARCH SPEED

navaho-atm 40000 SGI5 1000

• This gives a configuration of 1 host called navaho-atm , its pvmd task id, architecture and relative speed rating

add

• Additional hosts may be added using the add command

2 successful

HOST DTID

sioux-atm 100000

mohican-atm 140000

pvm> conf

3 hosts, 1 data format

HOST DTID ARCH SPEED

navaho-atm 40000 SGI5 1000

sioux-atm 100000 SGI5 1000

mohican-atm 140000 SGI5 1000

delete

• Hosts may be removed from the virtual machine using the delete command

1 successful

HOST STATUS

sioux-atm deleted

Executing a program

spawn

• The spawn command may used to execute a program from the pvm console

• This will direct the output from the program to the screen

Leaving PVM

quit, halt

• To exit from the console session while leaving all daemons and jobs running use the quit command

• To kill all pvm processes including the console, and then shut down PVM

Using a hostfile

• PVM may be started using a hostfile to define the virtual machine

• The hostfile lists the hosts in the user's virtual machine. In its simplest form it lists one host per line

• For example

navaho-atm

sioux-atm

• Options such as userid and passwd (lo and pw) may be specified for each host

• On versions prior to 3.3, the first host listed must be the computer on which PVM is initially started.

Error handling

• Generally in Fortran the completion status of a pvm routine may be checked, if the status >= 0 then the routine completed successfully, a negative value indicates that an error has occurred

• When an error occurs, a message is automatically printed that shows the task ID, function and error

• Automatic error reporting may be disabled by calling pvmfserror

• Error reports may be generated manually by calling pvmfperror

Debugging a PVM Application

• A task run by hand can be started under a serial debugger. Add PVMDEBUG to pvmfspawn arguments

• The following steps should be followed when debugging
  • Run program as a single task and debug as any other serial program

  • Run the program on a single host to eliminate network errors and errors in message passing

  • Run the program across a few hosts to locate deadlock and synchronization problems

  • Use XPVM

Fault Detection

• Pvmd will recover automatically, applications must perform their own error recovery

• A dead host will remain dead, but may be reconfigured later

• The pvmd to pvmd message passing system drives all fault detection

• Faults are triggered by retry time-out

Practical

• Logon and getting started

• Using the PVM Console