Nathan Hurst’s Blog

Who knew threads and romantic relationships had so much in common? For those of you new to threads, threads (and processes) allow computers to seemingly do multiple things at once, where each thing is a separate "thread" of execution. On a computer with a single processor, the processor spends short amounts of time executing each thread before switching to another thread to execute. On a multiprocessor system, processors execute threads simultaneously, switching between threads when there are more threads than processors.

For those of you new to romantic relationships, I don't have much advice for you other than: Don't tell your significant other that you're treating your relationship as a series of thread synchronization problems!

Also, I'm probably perpetuating some stereotypes here. Sorry, it just makes the examples easier.

Thread Synchronization Issues

Deadlock occurs when threads cannot proceed because they're waiting on each other.

Romantic relationship example: You and wife have to wake up at 6am to catch a flight. You half-wake-up at some point in the morning and think, "she'll wake me up," and go back to sleep. The problem is, now it's noon, and you've both been thinking the same thing for six hours. You missed your flight due to relationship deadlock.

Livelock occurs when threads cannot proceed because they're too busy responding to each other.

Romantic relationship example: When was the last time you heard an obnoxious couple talking on the phone? Think back to the end of their phone conversation. It probably ended like this.

1: Love you. Talk to you later.
2: Love you too. Bye.
... both wait ...
1: You hang up first.
2: No you hang up first.
1: No you...

You're witnessing relationship livelock. Neither person in the couple nor the couple as a whole can proceed because they're too busy responding to each other.

Starvation occurs when one thread is deprived of resources by greedy or mis-prioritized threads.

Romantic relationship example: You and your boyfriend share a checking account and deposit money into it on the first of the month. You routinely make small purchases every day. Your boyfriend rarely makes purchase, but when he does, he buys something big. After the first of the month, you successfully make your small purchases for a few days, but then your boyfriend buys an iPad. All your attempted purchases are now denied. You're suffering from starvation.

Race conditions occur when success depends on the order in which threads run.

Romantic relationship example: Your son wants to go bungee jumping with his friends. He knows that each parent requires that he ask both parents for permission. Using a clever turn of phrase, he realizes that he can exploit a relationship race condition to get what he wants by asking the stricter parent first.

Son (approaches strict mother): Can I go bungee jumping?
Mother: No, but ask your father.
Son (approaches lenient father): Can I go bungee jumping?
Father: Yes, but ask your mother.
Son: I already did.
Father: Great. Hope you have fun!

Thrashing occurs when threads make little or no progress due to the overhead of context switching.

Romantic relationship example: A couple tries to decide whether or not to get a pet. The argument gets heated. They keep bringing up unrelated topics. Each time a new topic comes up, they spend five minutes on it.

1: Having a dog would be so much fun!
2: You would never clean up after it.
1: What?! I clean all the time.
... five minutes later ...
1: Well at least I don't leave clothes all over the place.
2: Psh. I'm the only one that ever does the laundry. I can leave my clothes wherever I want.
... five minutes later ...
2: I don't know if I can talk about this anymore. I'm just going to go watch TV to cool down.
1: You watch TV all the time! We don't even need a pet. You spend all your time with the TV.

Every context switch gets the couple further away from where they started and from the problem they're trying to resolve. They're thrashing.

Busy waiting occurs when one thread continuously checks if it may proceed, robbing other threads of processing time.

Romantic relationship example: A couple is getting dressed for a party. The man is dressed and ready to go. The woman is nowhere near done. The man keeps interrupting the woman to ask her if she's ready yet. The man is busy waiting.

Self Promotion

If you're a developer and you like these sorts of problems, consider attending Hirelite: Speed Dating for the Hiring Process on Tuesday, April 27th in NYC where companies will be looking for great software people.