The button panel contains various buttons and menubuttons which control the execution of the slave program:
After executing one labelling step, the status line displays the default message Stopped and all displayed windows are updated to reflect the current state.
If STEP is pressed in the run mode (see RUN), the execution mode changes to the step mode and the program stops in the next labelling step.
When STEP is pressed together with the Shift key, the program executes one fine step: it stops as soon as a domain variable is modified. The updated variable with its new value will be highlighted, the status line shows the message Old domain: DOM, where DOM is the domain of this variable before its modification. The program then waits for a user action; only actions which can be executed asynchronously are accepted.
When the program fails after executing a fine step, the status line displays the message Failing and the program stops again. This gives the user the possibility to inspect the inconsistent state in detail, just before backtracking takes place. A new fine step after a failure will initiate backtracking and the program stops as soon as a new domain variable is modified, but it does not stop after variable domains have been reset to their previous values due to backtracking.
When the RUN button is pressed together with the Shift key, a series of fine steps is executed which stops either on failure, or success of the current labelling step. The former is a quick way to stop the execution immediately before backtracking so that the current state and reasons for failure can be inspected.
The whole process is executed only once, not until a fixpoint is reached and so it is possible that clicking several times on this button will result in more pruning (this is directly visible in the Size status field).
Looking ahead may be quite costly, because checking each domain element includes propagating changes and triggering related constraints. It can however provide important information about the real size of the search space.
CALL -1+7 - _222{[2, 4]}#\=0 EXIT -1+7 - _222{[2, 4]}#\=0 CALL -1-8+7#\=0 EXIT -1-8+7#\=0 CALL -1+8-7#\=0 **FAIL -1+8-7#\=0 CALL -5-7 + _262{[2, 4..7]}#\=0 EXIT -5-7 + _262{[2, 4..7]}#\=0 CALL -5+7 - _262{[2, 4..7]}#\=0 EXIT -5+7 - _262{[4..7]}#\=0