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1  Bitcoin / Bitcoin Technical Support / testnet3 peer IP's on: September 04, 2012, 06:59:35 PM
So the bitcoin with testnet3 can't find any peers.  Are there nodes I can add manually?
2  Bitcoin / Development & Technical Discussion / coin selection vs low value spam: non-deterministic failure on: August 25, 2012, 08:20:48 PM
If I run this program (v 0.6.99 on a testnet3-box with about 200 BTC balance), it succeeds about 1500 times and then fails with 'Error: Transaction creation failed, code: -4'.

b = jsonrpc.ServiceProxy(...)
for i in xrange(100000):
    print i
    a = b.getnewaddress('')
    b.sendtoaddress(a, 0.00000001)

debug.log shows: 'SelectCoins() best subset: ...' trying to pick up a massive set of small inputs.

Increasing the send amount usually gets it working again, but decreasing it back either fails immediately or eventually.

Isn't the implication here that you could destabilize a site by spamming them with low value transactions?  And increase their transaction fees when SelectCoins randomly picks up the low value inputs.

I think the solution for the coin selection is to sort the inputs from least 'encumbered' to most 'encumbered' (the value-age heuristic used to calculate tx fees), and just pick the inputs off the top, spam would then never get touched.  Possibly see how many inputs from the most 'encumbered' end can be included without increasing the transaction fee (to slowly eat the spam).  Or some clever global optimization.

Either way I think coin selection probably has to minimize the current transaction fee.
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