Re: [gecode-users] ask propagator

[Guido Tack]

Mauricio Toro wrote:

I have some questions about the concurrent constraint programming ask propagator.

I want to have this behavior:



1) In this propagator would it matter if I use domain
consistency or bounds consistency? which one should I use?

\textbf{blocking\_IF} $<boolean\_var>\ x0$ \textbf{then} $<ask\_body> \ procedureBody$ \textbf{else} $<skip>$

I'm not sure which part you're referring to. For the boolean control variable, there's no domain or bounds consistency really. You wait until it gets assigned and then run the body.

2) I am passing this function void (* procedureBody) (Space*) as an argument. If I would like to pass a closure, like an object with an executing method, instead of the function pointer. What kind of additional information should I include in the object?

Well, what do you plan to do in the object? That pretty much determines whether you need additional information. You'll have to have access to the variables, e.g., but you can of course get that by casting the Space* to its actual type.

3) What do you think about this header for the Ask Propagator:



  /**
   * \brief Concurrent Constraint Programming ASK propagator
   *
   * Requires \code #include "gecode/int/ask.hh" \endcode
   * \ingroup FuncIntProp
   */
  template <class View>
  class Ask : public UnaryPropagator<View,PC_INT_BND> {
  protected:
    using UnaryPropagator<View,PC_INT_BND>::x0;

Now you use an IntView for x0, but above you said x0 was a BoolVar.

    /// Constructor for cloning \a p
    Ask(Space* home, bool share, Ask& p);
    /// Constructor for posting
    Ask(Space* home, View x0, void (* procedureBody) (Space*));
  public:
    /// Copy propagator during cloning
    virtual Actor*     copy(Space* home, bool share);
    /// Perform propagation
    virtual ExecStatus propagate(Space* home, ModEventDelta med);
    /// Specification for this propagator
    virtual Reflection::ActorSpec spec(const Space* home,
                                        Reflection::VarMap& m) const;
    /// Post propagator according to specification
    static void post(Space* home, Reflection::VarMap& vars,
                     const Reflection::ActorSpec& spec);
    /// Mangled propagator name
    static Support::Symbol ati(void);
    /// Post bounds-consistent propagator

  };

/// \textbf{blocking\_IF} $<boolean\_var>\ x0$ \textbf{then} $<ask\_body>\ procedureBody$ \textbf{else} $<skip>$ static ExecStatus post(Space* home, View x0, void (* procedureBody) (Space*));

Yes, the rest looks ok.

Cheers,
        Guido

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