Hung Truong: The Blog!

Greplin Programming Challenge

I had some spare time on Monday and just read about Greplin getting some funding (and I guess they just went out of private beta today), so I did the Greplin Programming Challenge.

Unlike many programming challenges, the problems in this one were pretty easy to solve. I think a lot of people on Hacker News complained that you could basically brute force them into submission. For example, one question is finding a prime Fibonacci number. I'm sure there's super smart ways to do it but I just iterated through Fibs and then ran a really slow primeness function on each one. It worked eventually!

I finished the challenge and sent an email to the Greplin guys, since the challenge instructed me to do so. After reading through some of their site, the challenge actually started to make more sense to me. From their jobs page:

You should know the fastest way to do something – which sometimes means the least CPU cycles and sometimes means the least programmer cycles.

Basically, you could figure out the most efficient way to do the challenges (from a computational perspective) at a cost to programming time. Or you could recognize that N was trivially large for all of the challenge cases and just code something really simple up and get the answer. I picked the latter. Greplin is probably looking for both types, so I think they did a good job designing the challenge.

In other news, I signed up for their service and tried it out. It seems like a really cool concept and I like it so far. I kind of wish there was a roll your own version though. I dunno if I can trust Greplin with all of my innermost secrets… It's bad enough that Google has all of your email; Greplin can have that plus your tweets and Facebook stuff too!

Threadless Shirt – Tweet

I saw this new shirt on Threadless and was surprised it hadn't already done! Birds have probably known about Twitter for much longer than we have (early bird adopters). I like the fact that the Twitter interface has been recreated in a bird speech bubble, but I have a feeling the shirt will be outdated pretty soon (like when Twitter decides to come out with New New Twitter).

Get Tweet before it's outdated!

iAd Vs. AdMob – Clicks, Fill Rate, Impressions, eCPM and Revenue

About two weeks ago I updated one of my apps to use AdMob mobile ads when iAd fails to deliver (pretty damn often). Instead of swapping out iAd for AdMob, I use the iAd “didFailToReceiveAdWithError” delegate method to request an AdMob ad when iAd fails. This means that AdMob shouldn't take any income away from iAd, but only supplement it. I thought I'd take a look at the stats and compare the performance of the two ad networks on my app.

(The following numbers I'm referring to are from the time period from 1/25 to 2/7)

For an idea of scale, my app, Anime Nano, gets about 600 iAd requests per day. My app analytics software (Flurry) is saying I'm getting about 600 sessions per day. The thing is that about 1/5 of those sessions are on the iPad (and I haven't enabled iAd on the iPad yet), so I think that on average, the iPhone apps are making a little more than one iAd request per session.

Despite the fairly healthy rate of requests that I'm getting, iAds are only getting sent about 15% of the time. This percentage is what's known as the “fill rate.” This is also what most developers complain about being too low. The clickthrough rate is actually pretty good at 0.81%.

When iAd fails to deliver (85% of the time), I fall back to AdMob. The fill rate for AdMob is a high 88%, though the past few days it's been closer to 99%. The CTR, however, is a fairly low 0.25%, which is less than half of iAd. This is partly due to the fact that AdMob ads refresh more often, so the number of impressions is higher.

I'm going to describe my revenue in terms of percentages here since ad platforms typically don't like it when publishers publish their income. Not sure if that's changed lately, but whatever! In the time period from 1/25/2011 to 2/7/2011, I made 2.3x more with iAd than AdMob, even with the super low fill rate (and impressions) of iAd. This is pretty interesting since iAd only shows up 15% of the time. There were actually a few days where AdMob beat iAd, but there were a couple of days where iAd made a killing (relatively), probably from those super awesome interactive ads which I still haven't experienced firsthand yet.

For now, I'm content with the fill rate of AdMob, though it sort of pains me to see such a low click rate and revenue per click. Something tells me that if AdMob worked harder at increasing ad quality (like iAd), they'd be able to charge more and their advertisers would probably see a better return on investment. Most of the advertisers don't even bother to use an image ad, which I assume would increase the clickthrough rate.

I noticed something really strange when looking at ads on my app. There's no way for advertisers to disable ads on devices that already have the app installed. I keep seeing Amazon Kindle ads on both my iPad and my iPhone that already have the application installed. As a developer, I know there's a way to prevent those ads from showing by detecting whether the app is installed at runtime. I think this strange behavior happens on both iAd and AdMob. If anyone from either organization is reading this, contact me!

As far as the future of ads in mobile apps goes, I hope Apple will continue working on increasing the fill rate, and that AdMob tries to increase relevancy and ad quality. Right now it's really frustrating to see my “inventory” not live up to its revenue potential.

Instapaper Friendly – WordPress Plugin

While I was testing Instascriber , I noticed that the way that Instapaper was grabbing the content of my blog was a little off. The Instapaper for Publishers page describes how you can give Instapaper a hint on what your actual content is. I looked for a WordPress plugin that does this but didn't see anything, so I figured I'd do it myself.

Up to this point I had never made a WordPress plugin, so I had go figure that out first. It's relatively simple and there's a lot of good documentation out there. I just needed to hook into the “the_content” API hook and alter the content so it had a div surrounding it. The scary part is mostly that WordPress seems to give you a hella lot of control. So you could seriously eff things up with a simple plugin.

With this being my first plugin, I'm not completely sure it's been written the right way (kinda like when you make an edit on Wikipedia for the first time). Nevertheless, I'm making the plugin available. So let me know if there's something glaringly wrong with it. It's fairly simple, so I'm not sure exactly what could go wrong.

I made a special page for the plugin to live at, so get it at Instascriber Friendly – WordPress Plugin. You can also download it through the internal WordPress plugin search (look for ‘instapaper friendly').

Priceless: The Myth of Fair Value – Book Review

I just recently finished reading a book, so I better write up a review so I can collect my free Pizza Hut Personal Pan Pizza! I read about Priceless: The Myth of Fair Value on Aaron Swartz's 2010 Book Review (I'm trying to read as much as that dude does). Pricing has always been pretty interesting to me, so I figured a book about pricing would be a good, quick non-fiction read. Ironically, I opted to pay zero price for the book, borrowing it from the library instead of buying it.

Previously, I read Cheap: The High Cost of Discount Culture, which also concerned pricing, but mostly in the super cheap range. Priceless takes more of a psychological stab at human behavior. There are a few experiments that both books alluded to, like the Hershey's kiss experiment. Having read these two books (and the Freakonomics ones), I kind of think I should've been an economist.

Priceless starts out a bit slow by giving you a crash course in human psychology. Homo Economicus is described as a human who makes only rational decisions, and only the most rational. As a model, HomoEco is probably only useful in lab situations. As the book describes, human behavior is not only often irrational, but also very easy to manipulate. Priming and Anchoring are ways to change a person's opinion on something before they've even seen it.

The book gives this example. Research subjects were asked which percentage of the UN is comprised of African nations. Before that question, they were asked to give an over/under on a percentage. The percentage given was either really low (10%) or somewhat average (60%). The difference in that first question, is the percentage of African nations in the UN above or below (10/60%) affected their guess of what it actually was. The scary thing is that this works with many things, including pricing. Another experiment involved real estate and a differing list prices. Subjects (both normal people and real estate agents) were given list prices of a home and were asked to give a reasonable bid. Even the real estate professionals were susceptible to the anchoring effect of the suggested prices, though to a lesser degree.

After giving a solid scientific basis for human irrationality (specifically regarding pricing), the book goes through many short examples where the these effects were either exploited or tested in slightly different contexts. It's all pretty interesting stuff, especially to someone who feels they are above Jedi price tricks like me though I am probably not).

There are also a few methods described to try to ward against anchoring and priming. One is to immediately set up an argument. If someone says “do you think this book is worth 26.99?” and you say “yes,” then immediately think of reasons why it might be worth less than that. This is also why you should always take a friend with you to the car dealership to argue with.

Overall I thought the book was really interesting. If you can get past all of the cognitive science at the beginning (I might've found it boring because I had heard about most of it before), the second half of the book is a really quick and interesting read.