Martin Stone Davis wrote:
Okay, here's my problem with that: It's correct only if we are sure that we would actually get a successful result from some other node. But what if no other nodes return data, and we only get DNFs?

Well, this is where the concept of a "legitimate DNF" comes in. Let me refer you to the section on DNFs in:
http://freenetproject.org/index.php?page=ngrouting


Considering this possiblity, I would guess this formula would be better:

estimate=pSuccess+tSuccess
         +pFailure*(tFailure
                    +pGlobalSuccess*tGlobalSuccess
                    +pGlobalFailure*tGlobalFailure)

What exactly would that be an estimate *of*?


Recall that in NGR we always estimate "how long will it take to get the data if the message is (initially) routed to this node". It is important that we know what the estimate *means*. I don't think that is the case with the equasion you give above.

To illustrate how we might be going wrong in the current scheme, consider a key which figures to take a short time to retrieve when actually found, but is also hard to find. Then, our current globalEstimator would be low (optimistic) and lead us to towards trying more hares (fast but unlikely to succeed) than tortoises (slow but likely to succeed).

If that key takes a long time to find then the globalEstimator for it will not be low, since the global estimator takes *both* the search time and the transfer time into account.


I still don't see why our current approach doesn't achieve exactly the effect we want it to.

Ian.

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