12.4.7 Checkpoint and Restart Options
Since conformational searches can execute for long periods of time,
it is necessary to be able to save the state of search and restart it at
a later point in time. The CHECKPOINT and RESTART options
provide this capability. The frequency of checkpoints are also used to
specify the frequency of status writing operations. Finally, a checkpoint
is written at the end of the run, so that a long run that is terminated
by your options can be continued at greater length later.
The CHECKPOINT options are as follows:
- The UNIT options specifies what file unit the checkpoints
should be written to. If this is omitted or given a value of -1, then
no checkpoints are written. CONGEN handles the file attached to this
unit in a special way. When a checkpoint is about to be written, CONGEN
attempts to determine the name of the file associated with the unit.
It then issues an operating system command to rename or move the file
to a different name made up of the original name concatenated with _bak.
On VMS systems, any previous _bak file is deleted first.
Then, a new file with the original name is opened, and the checkpoint is
written. Thus, one good checkpoint file is always maintained, and usually there
- The NODEFREQ option specifies how many nodes must be allocated between writing
a checkpoint. The default is 100000.
- The TIMEFREQ option specifies the time in minutes between writing
checkpoint files. Checkpoints are written when either NODEFREQ or
TIMEFREQ tests are passed, and both the counters and timers are
reset when the checkpoint is written.
- This options controls when CONGEN periodically flushes the output
buffers for the log file (Fortran unit 6) and the output files specified
in the write coordinate degrees of freedom. This option is normally on,
but it can be turned off using NOFLUSH.
To restart a CONGEN run, one should edit the CONGEN input file that used
for the checkpoint file, and a RESTART option should be used. The
unit number specified in the RESTART option should be a valid
checkpoint from a previous run. It is permitted to change the options
which control the operation of search such as MAXNODE and
MAXLEAF, but the degrees of freedom must not be changed. Only
limited testing of option changing has been performed after restarting,
so be careful.