Statistics Predicates

The following predicates can be used to get execution statistics.

fd_statistics(?Key, ?Value)

This allows a program to access execution statistics specific to this solver. General statistics about CPU time and memory consumption etc. is available from the built-in predicate statistics/2.

For each of the possible keys Key, Value is unified with the current value of a counter, which is simultaneously zeroed. The following counters are maintained. See The Constraint System, for details of what they all mean:

resumptions

The number of times a constraint was resumed.

entailments

The number of times a (dis)entailment was detected by a constraint.

prunings

The number of times a domain was pruned.

backtracks

The number of times a contradiction was found by a domain being wiped out, or by a global constraint signalling failure. Other causes of backtracking, such as failed Prolog tests, are not covered by this counter.

constraints

The number of constraints created.

fd_statistics

Displays on the standard error stream a summary of the above statistics. All counters are zeroed.