Saved-states are just a special case of PO files. The
save_program/[1,2] predicate will save the execution state
in a file. The state consists of all predicates
and modules except built-in predicates and clauses
of volatile predicates, the current operator
declarations, the current character-conversion mapping,
the values of all writable Prolog flags except those marked as volatile
in ref-lps-flg,
any blackboard data (see ref-mdb-bbd), database data
(see ref-mdb-bas), and profiling data (see Execution Profiling); but no information for source-linked debugging.
A saved-state, can be restored using the restore/1
predicate from within Prolog:
| ?- restore(File).
which will replace the current program state by the one in File.
A saved-state can also be given as an option to the sicstus command:
% sicstus -r File
which will start execution by restoring File.
The save_program/2 predicate can be used to specify an initial goal
that will be run when the saved-state is restored. For example:
| ?- save_program(saved_state,initial_goal([a,b,c])).
When saved_state is loaded initial_goal/1 will be called. This allows
saved-states to be generated that will immediately start running the user's
program when they are restored. In addition to this save_program/2
facility, see also the initialization/1 facility to declare
goal to be executed upon loading (see Initializations).