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Parallel PEST
9-14
ppest case /r
where case.pst is the PEST control file for the current case. Alternatively, execution can be
re-commenced at that point at which calculation of the Jacobian matrix had most recently
been completed by typing the command:
ppest case /j
PSLAVE must be started in the usual fashion on each slave machine before issuing either of
these commands. Note, however, that if PSLAVE is already running on each of these
machines, it does not have to be restarted. This is because an already executing PSLAVE can
detect the commencement of a new PEST run.
If PEST is restarted without the “/r” or “/j” switch, it will commence the optimisation process
from the very beginning. Once again, if PSLAVE is already running on each of the slave
machines (having been initially started for the sake of a previous Parallel PEST run), it need
not be restarted on any of these machines. Such a re-commencement of PEST execution
“from scratch” will sometimes be warranted after PEST terminates execution with an error
message, or if the user terminates PEST execution with the “Immediate stop” option; in
neither case does PEST signal to its slaves to cease execution, just in case the user wishes to
restart PEST immediately after rectifying an error in the PEST control file or in a template or
instruction file. Note, however, that if changes are made to the run management file, each of
the slaves should be stopped and then re-started.
If PEST is restarted with the “/r” or “/j” switch, neither the PEST control file, nor any
template or instruction file should have been altered from that supplied to PEST on its
original run. It is important to note, however, that the same does not apply to the run
management file. Thus Parallel PEST can recommence a lengthy execution using more, less,
and/or different slaves than those that were used for the initial part of the Parallel PEST run,
as long as the new run management file is prepared in the correct fashion and PSLAVE
execution is recommenced on each of the slave machines identified in that file before PEST
execution is recommenced.
9.3.5 Parallel PEST Errors
As in normal PEST operation, Parallel PEST run-time error messages are written to both the
screen and the run record file.
9.3.6 Losing Slaves
If, during the course of a Parallel PEST run, a slave machine drops out of the network, under
many circumstances PEST will continue execution. If communications are lost during the
course of a model run, then PSLAVE executing on the lost machine will not be able to inform
PEST of the completion of that model run. PEST will soon grow tired of waiting and allocate
that run to another slave. It will thus continue execution with one less slave at its disposal.
However if the slave machine drops out just while PEST is trying to read a model output file,
PEST will terminate execution with an error message.
Even complete network failure may not result in the termination of a Parallel PEST run, for if
one slave is running on the same machine as PEST, PEST will be able to continue execution