Small correction - if the node is the trickle node it gets all invs, not just
the special quarter. This means that everything get distributed everywhere
every 12-15seconds, but a special quarter of the hash space is treated earlier,
so there is a meaning for vInvWait, but there is still a mismatch between
comments and code.
Cheers,
M
On 29/12/2011, at 23:05, Michael Grønager wrote:
In CNode::SendMessages there is a trickle algorithm. Judging from the
comments it is supposed to:
* at each update round a new (random) trickle node is chosen, with 120 nodes
and an average round time of 100ms (the sleep) we will have moved through
roughly all nodes every 12-15 seconds.
* when a node is the trickle node it will get to send all its pending
addresses to its corresponding peer.
* when a node is not trickle node (the rest of the nodes) we send
transaction-invs, however, only 1/4 of them - the rest is pushed to wait for
the next round and would eventually get sent.
However, the way the 1/4 of the invs are chosen is by:
(inv.getHash() ^ hashSalt) 3 == 0
As hashSalt is a constant (static, generated on start up) and as the hash of
an inv is constant for the inv too, the other 3/4 will never get sent and
hence it does not make sense to carry them around from round to round:
if (fTrickleWait) vInvWait.push_back(inv);
and:
pto-vInventoryToSend = vInvWait;
The hashSalt will be different for each node in the peer-to-peer network and
hence as long as we have much more than 4 nodes all tx'es will be sent around.
Ironically, this (wrong?) implementation divides the inv forwarding hash
space into 4, along the same lines as we discussed last week for DHTs...
I suggest to either keep the algorithm as is, but remove the redundant
vInvWait stuff, or to change the algorithm to e.g. push the tx'es into a
multimap (invHash^hashSalt, invHash) and choose the first 25% in each round.
The last alternative is that I have misunderstood the code... - if so please
correct me ;)
Happy New Year!
Michael
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