Ken Tilton wrote: > > I just keep what I call a "datapulse ID", sequentially growing from > zero, in a global variable. Each ruled Cell keeps track of its memoized > value, datapulse stamp, and whether it in fact changed value in reaching > its current datapulse stamp. (I can reach the current datapulse stamp by > determining no dependency (direct or indirect recursively down the > dependency graph) is both more current than me /and/ in fact changed in > value getting there.[1] If not, I take on the current datapulse but > never run my rule. Or, if yes, I run my rule but might compute the same > value as last time. Either way, I can flag myself as current but > not-actually-changed.) > ....
> > [1] Aha! I see a flaw. Arises if two datapulses pass before I (a cell > <g>) get read and must determine if my cache is obsolete, and some > dependency changed in the first datapulse but not the second. No, I do not think that can happen. I was conflating two mutually exclusive paths. If I am checking a dependency that means it would have notified me when it in fact changed. If my rule is running i will always get a valid value from a read. So i do not think there is a hole in there anywhere. In any case, I would not have needed a new last-changed-datapulse slot, i could just change the "changed" flag to be last-changed-datapulse. kenny -- Cells: http://common-lisp.net/project/cells/ "Have you ever been in a relationship?" Attorney for Mary Winkler, confessed killer of her minister husband, when asked if the couple had marital problems. -- http://mail.python.org/mailman/listinfo/python-list
