Ascend FD-23R Manual do Utilizador descarregar pdf (Página 32)

20 CHAPTER 1. The TOY(FD) System

fd statistics’ :: bool

• Deﬁnition: fd statistics’ always returns true and displays a set of useful statistics

(usually in the console).

• Example at the TOY(FD) command level

TOY(FD)> L== [X,Y,Z], domain L 1 4,

all_different’ L [complete true],

labeling [] L, fd_statistics’

Resumptions: 4

Entailments: 1

Prunings: 9

Backtracks: 0

Constraints created: 1

yes

L == [ 1, 2, 3 ]

X == 1

Y == 2

Z == 3

Elapsed time: 0 ms.

more solutions (y/n/d) [y]?

..........

fd statistics’/2

• Type declaration:

fd statistics :: statistics → int → bool

• Deﬁnition: ‘fd statistics Key V’ returns true if either

– V uniﬁes with the number of constraints created and also Key == con-

straints’ or

– V uniﬁes with the number of times that

1. a constraint is resumed and ‘Key == resumptions’,

2. a (dis) entailment was detected by a constraint and ‘Key == entailments’,

3. a domain was pruned and Key == prunings’‘,

4. a backtracking was executed because a domain becomes empty and Key ==

backtracks’.

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Ascend FD-23R Manual do Utilizador Página 32