BUG Report: Rounding glitch

July 17, 2010 at 2:10:03 PM UTC

Check this out...

I just installed 0.3.1 on two different machines and moved one bitpenny (0.01):

-= Before the transfer =-

[bitcoind@box1 ~]$ ~/bin/bitcoind getinfo
{
   "balance" : 1.150000000000,
   "blocks" : 68717,
   "connections" : 6,
   "proxy" : "",
   "generate" : false,
   "genproclimit" : -1,
   "difficulty" : 181.5432893640505
}

[bitcoind@box2 ~]$ ~/bin/bitcoind getinfo
{
   "balance" : 0.000000000000,
   "blocks" : 68717,
   "connections" : 22,
   "proxy" : "",
   "generate" : false,
   "genproclimit" : -1,
   "difficulty" : 181.5432893640505
}

-= AFTER the transfer =-

[bitcoind@box1 ~]$ ~/bin/bitcoind getinfo
{
   "balance" : 1.139999999999,
   "blocks" : 68717,
   "connections" : 10,
   "proxy" : "",
   "generate" : false,
   "genproclimit" : -1,
   "difficulty" : 181.5432893640505
}

[bitcoind@box2 ~]$ ~/bin/bitcoind getinfo
{
   "balance" : 0.010000000000,
   "blocks" : 68717,
   "connections" : 20,
   "proxy" : "",
   "generate" : false,
   "genproclimit" : -1,
   "difficulty" : 181.5432893640505
}

I personally think it is a display problem, but I can't be sure.. strange, no?

Both machines are running FreeBSD 7.2/amd64.

satoshi#2

Re: BUG Report: Rounding glitch

July 17, 2010 at 4:06:12 PM UTC

It must be a rounding error when getinfo converts to floating point to return the JSON-RPC result. The only place where it uses floating point to represent money is returning a value in JSON-RPC.

1.139999999999 is longer than bitcoin can internally represent.

internally, it could only be:
1.13999999 or
1.14000000

1.139999999999 is much much closer to 1.14000000 than 1.13999999, so it must be 1.14000000.

The code is this:
(double)GetBalance() / (double)COIN.

(I can't think of an easy way to fix it at the moment)