By the power of CTOR! Xthinner is now working with BCH mainnet blocks

A few hours ago, I fixed the last showstopping bug in my Xthinner code and got it running between two of my ABC full nodes on mainnet. One node serves as a bridge to the rest of the world, receiving Compact Blocks and transmitting Xthinner. The other is connected to no other nodes except this bridge.

The first block transmitted by Xthinner was #577,310. My nodes had just started when that block was published, so it was transmitted with only 24 transactions in mempool out of 2865 total in the block. It worked nonetheless. Xthinner has worked on every block since then, with no failures, and with no block taking more than 1.5 networking round trips. Most non-tiny blocks have gotten about 99% compression after fetching missing transactions, or about 99.3% before fetching. Eight blocks have been complete on arrival without any missing transaction fetching (0.5 round trips), and 24 blocks have required a round trip to fetch missing transactions.

I will probably make an alpha code release soon so that people can play around with it. The code still has some known bugs and vulnerabilities, though, so don't run it on anything you want to stay running.

Here's the best-performing block so far:

2019-04-08 09:27:53.076818 received: xtrblk (1660 bytes) peer=0 2019-04-08 09:27:53.077210 Filling xtrblk with mempool size 841 2019-04-08 09:27:53.077644 xtrblk: 841 tx, 1 prefilled 2019-04-08 09:27:53.077707 Received complete xthinner block: 000000000000000002f914b0c6afb568bec86b9a5166a5023f466c5ee7100e90. 2019-04-08 09:27:53.136257 UpdateTip: new best=000000000000000002f914b0c6afb568bec86b9a5166a5023f466c5ee7100e90 height=577332 version=0x20800000 log2_work=87.837579 tx=269896356 date='2019-04-08 09:27:30' progress=1.000000 cache=10.6MiB(79763txo) warning='40 of last 100 blocks have unexpected version' 

This was a 841 tx, 363 kB block transmitted in 1660 bytes. That's 99.54% compression or 15.79 bits/tx. Uncoincidentally, this was also one of the largest blocks so far, with 23 minutes elapsed since the prior block.

Bigger blocks get better compression because the header, coinbase, and checksum specification overhead is a smaller proportion of the whole, and sometimes also because the Xthinner algorithm can more consistently omit the initial bytes of the TXID.

Sizes of the xtrblk messages:

2019-04-08 06:17:48.394401 received: xtrblk (4511 bytes) peer=0 2019-04-08 06:34:40.219904 received: xtrblk (1249 bytes) peer=0 2019-04-08 06:50:25.290082 received: xtrblk (1209 bytes) peer=0 2019-04-08 06:51:49.082137 received: xtrblk (282 bytes) peer=0 2019-04-08 07:04:02.028427 received: xtrblk (416 bytes) peer=0 2019-04-08 07:09:44.603728 received: xtrblk (1235 bytes) peer=0 2019-04-08 07:15:32.338061 received: xtrblk (351 bytes) peer=0 2019-04-08 07:17:25.983502 received: xtrblk (839 bytes) peer=0 2019-04-08 07:19:38.947229 received: xtrblk (498 bytes) peer=0 2019-04-08 07:21:22.099113 received: xtrblk (404 bytes) peer=0 2019-04-08 07:37:20.573195 received: xtrblk (569 bytes) peer=0 2019-04-08 07:38:41.106193 received: xtrblk (1259 bytes) peer=0 2019-04-08 07:46:40.656947 received: xtrblk (764 bytes) peer=0 2019-04-08 07:52:40.203599 received: xtrblk (591 bytes) peer=0 2019-04-08 08:01:30.239679 received: xtrblk (776 bytes) peer=0 2019-04-08 08:26:06.212842 received: xtrblk (287 bytes) peer=0 2019-04-08 08:37:10.882075 received: xtrblk (2177 bytes) peer=0 2019-04-08 08:39:05.003971 received: xtrblk (392 bytes) peer=0 2019-04-08 08:40:27.191932 received: xtrblk (274 bytes) peer=0 2019-04-08 08:53:57.338920 received: xtrblk (1294 bytes) peer=0 2019-04-08 08:54:44.033299 received: xtrblk (344 bytes) peer=0 2019-04-08 09:04:55.541082 received: xtrblk (947 bytes) peer=0 2019-04-08 09:27:53.076818 received: xtrblk (1660 bytes) peer=0 2019-04-08 09:39:21.527632 received: xtrblk (878 bytes) peer=0 2019-04-08 09:48:57.831915 received: xtrblk (836 bytes) peer=0 2019-04-08 09:49:18.074036 received: xtrblk (243 bytes) peer=0 2019-04-08 09:52:09.949254 received: xtrblk (474 bytes) peer=0 2019-04-08 10:05:35.192227 received: xtrblk (451 bytes) peer=0 2019-04-08 10:12:37.671585 received: xtrblk (1317 bytes) peer=0 2019-04-08 10:12:40.761272 received: xtrblk (294 bytes) peer=0 2019-04-08 10:13:10.548404 received: xtrblk (278 bytes) peer=0 2019-04-08 10:17:06.108110 received: xtrblk (512 bytes) peer=0 

Sizes of the fetched missing transactions:

2019-04-08 06:17:48.410703 received: xtrtxn (842930 bytes) peer=0 2019-04-08 06:34:40.221133 received: xtrtxn (5691 bytes) peer=0 2019-04-08 06:50:25.291309 received: xtrtxn (517 bytes) peer=0 2019-04-08 07:04:02.029652 received: xtrtxn (3461 bytes) peer=0 2019-04-08 07:09:44.604922 received: xtrtxn (744 bytes) peer=0 2019-04-08 07:15:32.339450 received: xtrtxn (1155 bytes) peer=0 2019-04-08 07:17:25.984684 received: xtrtxn (3337 bytes) peer=0 2019-04-08 07:19:38.948412 received: xtrtxn (654 bytes) peer=0 2019-04-08 07:21:22.100418 received: xtrtxn (3510 bytes) peer=0 2019-04-08 07:37:20.574477 received: xtrtxn (3990 bytes) peer=0 2019-04-08 07:38:41.107558 received: xtrtxn (519 bytes) peer=0 2019-04-08 07:52:40.204659 received: xtrtxn (2364 bytes) peer=0 2019-04-08 08:01:30.240842 received: xtrtxn (275 bytes) peer=0 2019-04-08 08:26:06.214200 received: xtrtxn (274 bytes) peer=0 2019-04-08 08:39:05.005097 received: xtrtxn (273 bytes) peer=0 2019-04-08 08:53:57.340233 received: xtrtxn (514 bytes) peer=0 2019-04-08 08:54:44.034397 received: xtrtxn (1243 bytes) peer=0 2019-04-08 09:04:55.542438 received: xtrtxn (420 bytes) peer=0 2019-04-08 09:39:21.528842 received: xtrtxn (811 bytes) peer=0 2019-04-08 09:49:18.075155 received: xtrtxn (274 bytes) peer=0 2019-04-08 09:52:09.950762 received: xtrtxn (10478 bytes) peer=0 2019-04-08 10:05:35.193791 received: xtrtxn (8248 bytes) peer=0 2019-04-08 10:12:40.762645 received: xtrtxn (1741 bytes) peer=0 

submitted by /u/jtoomim
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