Vol. 10 No. 4 – April 2012


Realtime Computer Vision with OpenCV:
Mobile computer-vision technology will soon become as ubiquitous as touch interfaces.

Computer vision is a rapidly growing field devoted to analyzing, modifying, and high-level understanding of images. Its objective is to determine what is happening in front of a camera and use that understanding to control a computer or robotic system, or to provide people with new images that are more informative or aesthetically pleasing than the original camera images. Application areas for computer-vision technology include video surveillance, biometrics, automotive, photography, movie production, Web search, medicine, augmented reality gaming, new user interfaces, and many more.

by Kari Pulli, Anatoly Baksheev, Kirill Kornyakov, Victor Eruhimov

A System is not a Product:
Stopping to smell the code before wasting time reentering configuration data

Every once in a while, I come across a piece of good code and like to take a moment to recognize this fact, if only to keep my blood pressure low before my yearly medical checkup. The first such piece of code to catch my eye was clocksource.h in Linux. Linux interfaces with hardware clocks, such as the crystal on a motherboard, through a set of structures that are put together like a set of Russian dolls.

by George V. Neville-Neil

CPU DB: Recording Microprocessor History:
With this open database, you can mine microprocessor trends over the past 40 years.

In November 1971, Intel introduced the world’s first single-chip microprocessor, the Intel 4004. It had 2,300 transistors, ran at a clock speed of up to 740 KHz, and delivered 60,000 instructions per second while dissipating 0.5 watts. The following four decades witnessed exponential growth in compute power, a trend that has enabled applications as diverse as climate modeling, protein folding, and computing real-time ballistic trajectories of angry birds. Today’s microprocessor chips employ billions of transistors, include multiple processor cores on a single silicon die, run at clock speeds measured in gigahertz, and deliver more than 4 million times the performance of the original 4004.

by Andrew Danowitz, Kyle Kelley, James Mao, John P. Stevenson, Mark Horowitz

Idempotence Is Not a Medical Condition:
An essential property for reliable systems

The definition of distributed computing can be confusing. Sometimes, it refers to a tightly coupled cluster of computers working together to look like one larger computer. More often, however, it refers to a bunch of loosely related applications chattering together without a lot of system-level support. This lack of support in distributed computing environments makes it difficult to write applications that work together. Messages sent between systems do not have crisp guarantees for delivery. They can get lost, and so, after a timeout, they are retried. The application on the other side of the communication may see multiple messages arrive where one was intended. These messages may be reordered and interleaved with different messages. Ensuring that the application behaves as intended can be very hard to design and implement. It is even harder to test.

by Pat Helland