Re: Incremental Data Structures

[David Mechner <mechner@xxxxxxxxxxxxxxxxx>]

Serge Boisse STNA 7P (33) 562 14 5731 wrote:
> David Mechner wrote:
> >
> > Incremental update done by storing changes adds substantial complexity
> > to the program, and requires a great deal of effort to design and
> > implement. It has the advantage that, if done well, is nearly
> > transparent and puts no pressure on you to steer clear of complex or
> > expensive algorithms, allowing you to concentrate on generating the
> > information that you think best allows you to solve problems in go.
> 
> Wrong. it is not transparent at all if the structure is complex : 
> [objects' addresses change as a result of reading and/or backtracking]

We also made this mistake when we first implemented the system. What we
do now to avoid this problem is copy the value of the saved version back
to the original location in memory when we revert so all preexisting
references to objects remain valid. It's quite transparent.

Tim and I will post the source code for our revertable object system
shortly.

-David

-- 
David A. Mechner            Center for Neural Science
mechner@xxxxxxxxxxxxxxxxx         4 Washington Place, New York, NY 10003
212.998.3580                http://cns.nyu.edu/~mechner/