7 ms·
Reminds me of the cable lengths for black boxes connected to the network in Wall Street. Each cable is the same length regardless of which computer is closer to
by gareth_untether 4y ago
Reminds me of the cable lengths for black boxes connected to the network in Wall Street. Each cable is the same length regardless of which computer is closer to the access point.
- Misdicorl 4y agoPerhaps apocryphal/silly, but amusing nonetheless. Story goes that this means you want to be in the computer furthest from the interconnect because light travels slightly faster in straight fiber than in coiled fiber.
- colejohnson66 4y agoNot apocryphal; IEX has 38 miles of wire in their building. Tom Scott did a video a few years ago about it: https://www.youtube.com/watch?v=d8BcCLLX4N4 https://www.youtube.com/watch?v=d8BcCLLX4N4
- vmception 4y agoDoes IEX have any liquidity or uptake yet?
- infinityio 4y agoApparently they have 2.6% market share for trading in the US?
- Nition 4y agoI think Misdicorl meant that their story of wanting to be the furthest away is perhaps untrue, not the cables.
- Humdeee 4y agoI work in this space and although true (this is called modal dispersion), there are compensation techniques always used in termination equipment to 'handicap' or mitigate these occurrences. Not perfect, but very, very, very small deltas. Unsure if it's enough to act upon without knowing the length from output to next input.
- jakey_bakey 4y agoThat's neat, I didn't know about this. Very cool.
- jedberg 4y agoI never understood why they didn't use randomized length micro batches to solve this. Instead of processing orders instantly, wait between 200ms and 500ms and then process all orders that came in that window in random order. Then being 5ms closer to the server wouldn't matter.
- axg11 4y agoThat sounds like a complex solution. Sometimes a dumb solution that works good enough is better than a complex solution that _probably_ can't be exploited.
- jedberg 4y agoIt's complex on one end to reduce complexity on the other -- the trading companies wouldn't have to worry about millisecond optimizations if they trading batches were 200ms windows. So the wire lengths wouldn't matter but also not mattering is the processor, memory, software, etc. for the trading companies. Seems like a good tradeoff. And honestly the wire thing probably isn't real. Light moves 30cm in a nanosecond. The wire lengths could be 3 meters different and only make a 10ns difference. Not sure that would matter all that much.
- axg11 4y agoI used to work in HFT. I promise you that companies would still try to exploit randomized batches. There is an advantage to being the very last entrant into a batch (most up to date information). Truly random batches are not trivial to implement and any statistical pattern in the batching could be exploited.
- jerf 4y ago"Truly random batches are not trivial to implement and any statistical pattern in the batching could be exploited." If an HFT manages to exploit a correctly implemented entropy-pool random number generator using AES-256 to extend the stream as needed, they're welcome to pick up a few more bucks as far as I'm concerned. Yes, problems have existed before but I'm sure in this case we can assume high-assurance and careful programming, not some fresh grad being assigned the problem and thinking linear congruential generators sound really cool.