August 12, 2019
Yes, I had help with the graphics for this series. There's no way I'd have animated that myself! On that note, thanks to Dashlane for sponsoring and helping me hire an animator: their free trial link is https://www.dashlane.com/tomscott
>If you are in computer science and working on a problem that involves potential loss of life, I really hope you aren't watching a series called "The Basics".But they're fun!
Why do kids toys adverts have to say “batteries not included?”
2 Generals is an interesting conundrum in and of itself but I think it's a poor paradigm for avoiding the processing of repeated messages. In 2 Generals, no one proceeds without an acknowledgment. It's a Schrodinger's Cat problem. You don't know the answer until 8 p.m. when either everyone is at the castle or is still waiting for another acknowledgment. Applying idempotency (which would be against the "strict" rules) to 2 Generals, still wouldn't solve the problem. It would only affirm that additional messages, if any, are the same (attack at 8 p.m.), and only if the messages actually make it. 2 Generals doesn't guarantee message delivery in either direction, so even with idempotency tokens, Army B may still take no action if they don't get their acknowledgment.With the delivery issue, if the additional messages don't make it, it doesn't matter, the other side will respond appropriately to the original message. In delivery, the return acknowledgment goes far beyond the 2 Generals' (receipt of message), as you can get an erroneous message, a success or failure, and is likely not to have an effect on processing if no acknowledgment is sent.In any case, I think the delivery problem and applications of idempotency tokens as you've described, is its own best explanation of what's going on, not 2 Generals, which idempotency can't be used to solve (again strict rules).
General A sends "8pm" General B sends "8pm ack" - General a doesn't attack unless it receives the ack...
General A sends 2 Messengers. Both go to general B to confirm the message was received. Both go to General A but when passing the castle at the exact halfway point one messenger goes back to general b the other goes on to a. They both know the message was received by general b and the acknowledgement got through back to a.
An interesting follow up would be the Byzantine general's problem - what if there were multiple generals that could back stab each other?
Hey, I'm allowed to watch a series called "The Basics" even if I am working on safety of flight software!
At the point where he's talking about sending 200 messengers, and I'm thinking of a solution right now, I will see how wrong I am once I finish the video.General A sends a messenger to meet a messenger sent by General B half way to the valley, one with a letter of an estimated time and another of "Hey, here's my letter"The messengers swap messages, both now know that once they leave the 50% point they're free of danger. They make their way back to their sending General with the opposing General's note in hand.Repeat this process once the messenger arrives at their designated outpost, this time with the other General agreeing (or disagreeing) with the time. If they disagree, repeat this process.Now they have the correct schedule and a guarantee that the messenger has arrived.Edit: I guess I was incorrect, although my answer wasn't explored. I would assume that it would cause more margin of error though.I still don't understand the concept of an idempotence key, sure you're ensuring nothing if fulfilled twice, but what if it breaks to begin with? There's no way for the other side to know...
You are so handsome hehe I like your channel! Greats from Brazil.
The example was weak, imo. But good info.
their is an almost guaranteed way to get it to workgeneral A sends a message, general B continues to send a message until general A responses, if another messenger from general B arrives, General A can assume general B didnt receive the message, and send another message, once General As messenger arrived, at which point no more messages from general B will arrive, so they both attackedit: this is under the assumption that the fail rate of messengers is below 100% and their is plenty of time between attacks