Latency Hiding

A few weeks ago, James Morle posted an article called "Latency hiding for fun and profit." Latency hiding one of the fundamental skills that, I believe, distinguishes the people who are Really On The Ball from the people who Just Don't Get It.

Last night, I was calling to my 12-year old boy Alex to come look at something I wanted him to see my computer. At the same time, his mom was reminding him to hurry up if he wanted something to eat, because he only had five minutes before he had to head up to his bedroom. "Alex, come here," I told him, putting a little extra pressure on him. "Just a second, Dad." I looked up and notice that he was unwrapping his ready-made ham and cheese sandwich that he had gotten out of the freezer. He dropped it into the microwave and initiated its two-minute ride, and then he came over to spend two minutes looking at my computer with me while his sandwich cooked. Latency hiding. Excellent.

James's blog helped me put a name to a game that I realize that I play very, very often. Today, I realized that I play the latency hiding game every time I go through an airport security checkpoint. How you lay your stuff on the X-ray machine conveyor belt determines how long you're going to spend getting your stuff off on the other side. So, while I'm queued for the X-ray, I figure out how to optimize my exit once I get through to the other side.

When I travel every week, I don't really have to think too much about it; I just do the same thing I did a few days ago. When I haven't been through an airport for a while, I go through it all in my mind a little more carefully. And of course, airport rules change regularly, which adds a little spice to the analysis. Some airports require me to carry my boarding pass through the metal detector; others don't. Some airports let me keep my shoes on. Some airports let me keep my computer in my briefcase.

Today, the rules were:

• I had my briefcase and my carry-on suitcase.
• Boarding pass can go back into the briefcase.
• Shoes off.
• 1-quart ziplock back of liquids and gels: out.
• MacBook: out.

Here's how I put my things onto the belt, optimized for latency hiding. I grabbed two plastic boxes and loaded the belt this way:

1. Plastic box with shoes and ziplock bag.
2. Suitcase.
3. Plastic box with MacBook.
4. Briefcase.

That way, when I cleared the metal detector, I could perform the following operations in this order:

1. Box with shoes and ziplock bag arrive.
2. Put my shoes on.
3. Take the ziplock bag out of the plastic box.
4. Suitcase arrives.
5. Put the ziplock bag back into my suitcase.
6. Box with MacBook arrives.
7. Take my MacBook out.
8. Stack the two boxes for the attendant.
9. Briefcase arrives.
10. Put the MacBook into the briefcase.
11. Get the heck out of the way.

Latency hiding helps me exit a slightly uncomfortable experience a little more quickly, and it helps me cope with time spent queueing—a process that's difficult to enjoy—for a process that's itself difficult to enjoy.

I don't know what a lot of the other people in line are thinking while they're standing there for their 15 minutes, watching 30 people ahead of them go through the same process they'll soon endure, 30 identical times. Maybe it's finances or football or cancer or just their own discomfort from being in unusual surroundings. For me, it's usually latency hiding.