addchain | Compute addition chains using three methods | Learning library

I'm working on your question and have made some progress -- at least I have a revision of your code with some troubleshooting additions to it, and a revision of the Interface. I can't figure out how to attach a model here, or an image of the view you will see when you run it, so I posted the full model and a PNG file in the netlogo-users Google Group.

The revisions do not fully answer your question about how to solve the breaking up of the chain, but they provide a reproducible version of the model that you can be sure will break at step 746 and that you can turn on dense printing and slow action and watch what is going on with attempted moves after that.

Maybe if we both look at that it will be obvious why this is breaking.

One thing I think may be happening is that, once two cells link and tie, your move algorithm no longer is the correct logic for how the knotted chain should move.

Here's the changes that I made:

• I added a random-seed command in setup so that the model can be repeatedly run with exactly the same choices in random variables, so we can both look at the results.

• I added a "verbose?" switch on the Interface to turn on or off detailed printing of what's going on.

• I added a "clear-stop" button that will allow the "stop" commands I put in the model to stop the running using a stop-requested? flag, which the code sets and this button resets so that "go" and "one step" work again after a stop and the ticks counter keeps on incrementing.

• I added a msec-per-tick slider to put a fixed number of milliseconds at the end of the go step so the model will run at a speed that is usable for debugging. I don't know how other people can do it -- when I try to use the built-in slider at the top of the interface to control speed, either it's way too slow, or it's way too fast, and I can't seem to be able to tweak it to just right. So I added this kludge.

• I guessed what limits you had on your wigglefactor slider on your interface and made one that goes from 0 to 90 (degrees). It works ok and reproduces your bug.

• I added some additional tests to prevent the two C-cells that are adjacent in your choice of cells from linking to each other when they discover, as they do sometimes, that they are on the same patch. With a random seed of 23456 your original code ties its own CC adjacent pair together in tick 2 for instance.

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Here's the revised code, and comments as to how to use it are in the posted model (in netlogo-users) and below after the code as well.