When I switched from working on Yelp’s iPhone app to our Android app, one of the first things I encountered was the radical difference between the equivalent classes to handle what I normally consider a “screen” or “page” of an app. On Android, an Activity handles what on iOS you use a UIViewController for, but they work in fundamentally different ways. One of the biggest differences is that on Android you can’t just instantiate a new Activity and display it like you can with a UIViewController. Instead you create an Intent and tell the system to start an Activity based...

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Here in Yelp Engineering, we spend lots of time working on useful and cool stuff for Yelp users of all sorts—consumers, business owners, and even our own Community Managers. Sometimes though, it’s nice to take a break and go hang out with your coworkers for a bit. What better place to “hang out” than a few feet up in the air? Our most recent offsite took us to House of Air, a giant indoor trampoline park. After getting a brief safety introduction from HoA’s “Flight Crew” the team hit the trampolines, and well… I think these say it all: Of...

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At Yelp, we store nearly all of our data in MySQL. At any given time we’re issuing tens of thousands of SQL queries to our database cluster per second, with some individual servers going above the 10k qps mark. Our database cluster consists of billions of rows. In response to a lot of different problems we’ve had to optimize the snot out of our MySQL installation, and we’ve learned some interesting things along the way. A colleague and I recently gave a presentation to some of our coworkers, titled  MySQL Minutiae & InnoDB Internals. The talk covered some good background knowledge that every developer should...

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Here at Yelp, we’re passionate about building things; it’s at the core of our engineering philosophy. In fact, we enjoy it so much that many of us keep on building after we finish work. I recently found some spare time to work on an interesting project with the Microsoft Kinect. I think it’s a cool start and I’ve open sourced the code so that others can build something even cooler. Easy Skeletal Tracking If you’re reading this blog, you’re likely familiar with the Microsoft Kinect. It combines an RGB camera, an infrared laser projector, and an infrared camera to determine...

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Over the next couple of weeks, Yelp is going to be hosting two open-to-the-public events for members of the software development community: PyPy Just-in-Time Interpreters March 3rd, 6pm Armin Rigo of the PyPy project will be giving a presentation on achievements made by PyPy, the “fastest, most compatible, and most stable ‘alternative’ Python interpreter.” Special attention will be given to advancements in the area of dynamic (JIT) interpreters. You can find more information on SFPython’s Meetup page. If you plan to come, make sure to RSVP at least a day in advance so that security will allow you into the...

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Alan on our iPhone team recently encountered a tricky bug that had to do with the ObjectiveC compiler and differences in architecture between ARM and x86. The Problem On the device (but not the sim), the following code would crash on views that implemented drawInRect methods that returned a CGPoint (instead of having a void return type like other drawInRect methods). for (id view in _subviews) { [view drawInRect:[view frame]]; } To make matters weirder, the pointer ‘view’ before stepping into drawInRect was not the same as the pointer ‘self’ after stepping into drawInRect! However, by typecasting view to the...

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In addition to having written over 15 million reviews, Yelpers also contribute hundreds of thousands of business listing corrections each year.  Not all of these corrections are accurate, though, and there are quite a few jokers out there (e.g. suggesting the aquariums category for popular seafood restaurants… very funny!).  Yelp is serious about the correctness of business listings, so in order to efficiently validate each and every change, we’ve turned to Amazon’s Mechanical Turk (AMT) as well as other automated methods.  We recently published a research paper [1] at the NIPS 2010 Workshop on Computational Social Science and the Wisdom...

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Click your heels together and say the magic words three times: “there’s no place like Yelp…there’s no place like Yelp…there’s no place like Yelp.” Then perhaps you’ll be whisked away to the land of Yelp Engineering where our third Hackathon just wrapped up. Like the previous Hackathon and the one before that, this 48-hour period where engineers were set loose to work on “anything you wouldn’t normally be able to work on that might be useful, funny, or cool” (and ostensibly, related at least indirectly to Yelp) resulted in some awesome creations. One of the biggest milestones for our third...

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