[Bitcoin-development] Trickle in CNode::SendMessages

Michael Grønager gronager at ceptacle.com
Fri Dec 30 07:38:22 UTC 2011

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.



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
> ------------------------------------------------------------------------------
> Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex
> infrastructure or vast IT resources to deliver seamless, secure access to
> virtual desktops. With this all-in-one solution, easily deploy virtual 
> desktops for less than the cost of PCs and save 60% on VDI infrastructure 
> costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development

Michael Gronager, PhD
Owner Ceptacle / NDGF Director, NORDUnet A/S
Jens Juels Gade 33
2100 Copenhagen E
Mobile: +45 31 62 14 01
E-mail: gronager at ceptacle.com

More information about the bitcoin-dev mailing list