Constraint

From Dyna

trmonc4t boricnoc If you are doing constrained optimization with DynaMITE, your program should specify what the constraints are. You should assert or derive items of the form

constrain(item==value)

or

constrain(item >= value)

For example, suppose you have written a probabilistic CKY parser. You want to require that all the rewrite rules with a given left-hand side sum to one. So you write

sum_lhs(Lhs) += rewrite(Lhs,_).              % unary rewrite rule
sum_lhs(Lhs) += rewrite(Lhs,_,_).            % binary rewrite rule
constrain(sum_lhs(Lhs)==1) |= ?sum_lhs(Lhs). % we constrain sum_lhs(np) if it was derived,
                                             % i.e., if there were any rules with np as lhs

If your rewrite rule probabilities are in the logarithmic domain, you would write

logsum_lhs(Lhs) log+= rewrite(Lhs,_).       
logsum_lhs(Lhs) log+= rewrite(Lhs,_,_).     
constrain(logsum_lhs(Lhs)==0) |= ?sum_lhs(Lhs).

Of course, a given version of DynaMITE can only handle certain kinds of constraints. The current version can handle sum-to-one constraints in the log domain, as shown above.

At the moment, DynaMITE expects a slightly different form: constrain_eq(item,value). Also at the moment, you need to explicitly declare :- oldquery(constraints, constrain_eq(_,_)). This will become unnecessary in future (and perhaps even invalid, since oldquery is deprecated).