Subway waiting math

2016-07-09

Why does it suck to wait for things? In a previous post I analyzed a NYC subway dataset and found that at some point, quite early, it’s worth just giving up.

This isn’t a proof that the subway doesn’t run on time – in fact it might actually proves that the subway runs really well. The numbers indicate that it’s not worth waiting after 10 minutes, but it’s a rare event and usually involves something extraordinary like a multi-hour delay. You should roughly give up after some point related to the normal train frequency, and 10 minutes is not a lot at all. Conversely if the trains ran hourly, it probably would had been worth waiting an hour or more. My analysis gave me a lot of respect for the job MTA is doing.

Approximate nearest news

2016-06-02

As you may know, one of my (very geeky) interests is Approximate nearest neigbor methods, and I’m the author of a Python package called Annoy.

I’ve also built a benchmark suite called ann-benchmarks to compare different packages. Annoy was the world’s fastest package for a few months, but two things happened.

What is your motivation?

2016-05-24

I’ve been trying to learn Clojure. I keep telling people I meet that I really want to learn Clojure, but still every night I can’t get myself to spend time with it. It’s unclear if I really want to learn Clojure or just want to have learned Clojure?

Dollar cost averaging

2016-04-26

(I accidentally published an unfinished draft of this post a few days ago – sorry about that).

There’s a lot of sources preaching the benefits of dollar cost averaging, or the practice of investing a fixed amount of money regularly. The alleged benefit is that when the price goes up, well, then your stake is worth more, but if the price goes down, then you get more shares for the same amount of money. According to Wikipedia, it “minimises downside risk”, about.com says it “drastically reduces market risk”, and an article on Nasdaq.com claims that it’s a “smart investment strategy”.

Why organizations fail

2016-04-18

One of my favorite business hobbies is to reduce some nasty decision down to its absolute core objective, decide the most basic strategy, and then add more and more modifications as you have to confront the complexity of reality (yes I have very lame hobbies thanks I know).

NYC subway math

2016-04-04

Apparently MTA (the company running the NYC subway) has a real-time API. My fascination for the subway takes autistic proportions and so obviously I had to analyze some of the data. The documentation is somewhat terrible, but here’s some relevant code for how to use the API:

Exploding offers are bullshit

2016-03-16

I do a lot of recruiting and have given maybe 50 offers in my career. Although many companies do, I never put a deadline on any of them. Unfortunately, I’ve often ended up competing with other companies who do, and I feel really bad that this usually tricks younger developers into signing offers. On numerous occasions, I’ve gotten an email halfway through the interview process

Meta-blogging

2016-03-12

(This is not a very relevant/useful post for regular readers – feel free to skip. I thought I would share it so people can find it on Google.)

My blog blew up twice in a week earlier this year when I landed on Hacker News. The first time I was asleep so I didn’t notice that the site went down. The second time I did notice, and scrambled to reconfigure Apache & MySQL to handle the load.

Iterate or die

2016-03-02

Here’s a conclusion I’ve made building consumer products for many years: the speed at which a company innovates is limited by its iteration speed.

I don’t even mean throughput here. I just mean the cycle time. Invoking Little’s law this is also related to the total inventory of features not being deployed yet.