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Looping dependencies

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Luca Billi

Looping dependencies

I noticed that the current implementation of LazyObjects generates
infinite recursions
in the case the dependency hierarchy among Observer/Observable objects
contains loops.

A suggestion to break the infinite recursion is to replace the update()
method as follows:

void LazyObject::update() {

if (!frozen_&& calculated_){
//
// Set calculated_=false before calling notifyObservers()
//
calculated_ = false;

notifyObservers();
}

calculated_ = false;
}

Luca

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Luigi Ballabio

Re: Looping dependencies

Luca,
thanks for the report. Ferdinando applied your changes to the repository.

Luigi

On Sun, Feb 5, 2012 at 9:26 PM, Luca Billi <[hidden email]> wrote:

> I noticed that the current implementation of LazyObjects generates
> infinite recursions
> in the case the dependency hierarchy among Observer/Observable objects
> contains loops.
>
> A suggestion to break the infinite recursion is to replace the update()
> method as follows:
>
> void LazyObject::update() {
>
> if (!frozen_&& calculated_){
> //
> // Set calculated_=false before calling notifyObservers()
> //
> calculated_ = false;
>
> notifyObservers();
> }
>
> calculated_ = false;
> }
>
>
> Luca
>
> ------------------------------------------------------------------------------
> Try before you buy = See our experts in action!
> The most comprehensive online learning library for Microsoft developers
> is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
> Metro Style Apps, more. Free future releases when you subscribe now!
> http://p.sf.net/sfu/learndevnow-dev2
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> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/quantlib-dev

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Ferdinando M. Ametrano-3

Re: Looping dependencies

In reply to this post by Luca Billi

Hi Luca

On Sun, Feb 5, 2012 at 9:26 PM, Luca Billi <[hidden email]> wrote:
> I noticed that the current implementation of LazyObjects generates
> infinite recursions
> in the case the dependency hierarchy among Observer/Observable objects
> contains loops.
>
> A suggestion to break the infinite recursion is to replace the update()
> method as follows:

> [...]

good catch, even if on the 1.2.0 release branch it was already fixed as in the following

inline void LazyObject::update() {
// forwards notifications only the first time
if (calculated_) {
// set to false early, otherways non-lazy observers would be
// served obsolete data because of calculated_ being still true
calculated_ = false;
// observers don't expect notifications from frozen objects
if (!frozen_)
notifyObservers();
}
}

I've added your "prevent infinite recursion" comment too

ciao -- Nando