Category: CS

Al Gore‘s film and gradually more assertive and thorough science has managed to mostly shift the debate on climate change from “Is it happening?” to “What should be done?” In that context, it’s worthwhile to think a bit about what can be done within computer science research.

There are two things we can think about:

1. Doing Research At a cartoon level, computer science research consists of some combination of commuting to&from work, writing programs, running them on computers, writing papers, and presenting them at conferences. A typical computer has a power usage on the order of 100 Watts, which works out to 2.4 kiloWatt-hours/day. Looking up David MacKay‘s reference on power usage per person, it becomes clear that this is a relatively minor part of the lifestyle, although it could become substantial if many more computers are required. Much larger costs are associated with commuting (which is in common with many people) and attending conferences. Since local commuting is common across many people, and there are known approaches (typically public transportation) for more efficient commuting, I expect researchers can piggyback on improvements in public transportation to reduce commuting costs. In fact, the situation for researchers may be better in general, as the nature of the job may make commuting avoidable, at least on some days.

   Presenting at conferences is the remaining problem area, essentially due to travel by airplane to and from a conference. Travel by airplane has an energy cost similar to travel by car over the same distance, but we typically take airplanes for very long distances. Unlike cars, typical airplane usage requires stored energy in a dense form. For example, there are no serious proposals I’m aware of for battery-powered airplanes, because all existing rechargeable batteries have a power density around 1/10th that of hydrocarbon fuel (which makes sense given that about 3/4 of the mass for a hydrocarbon fire is oxygen in the air). This suggests airplane transport may be particularly difficult to adapt towards low or zero carbon usage. The plausible approaches I know involve either using electricity (from where?) to inefficiently crack water for hydrogen, or the biofuel approach where hydrocarbons are made by plants, with neither of these approaches particularly far along in development. If these aren’t developed, it seems we should expect fewer conferences, more regional conferences, Europe with it’s extensive fast train network to be less impacted, and more serious effort towards distributed conferences. For the last, it’s easy to imagine with existing technology having simultaneous regional conferences which are mutually videoconferenced, and we aren’t far from being able to handle a fully interactive videobroadcast amongst an indefinitely large number of participants. As a corollary of fewer conferences, other interactive mechanisms (for example research blogs) seems likely to grow.

2. Research Topics They keyword for research topics is efficiency, and it is not a trivial concern on a global scale. In computer science, there have been a few algorithms (such as quicksort and hashing) developed which substantially and broadly improved real-world efficiency, but the real driver of efficiency so far is the hardware development, which has phenomenally improved efficiency for several decades.

   Many of the efficiency improvements are sure to remain hardware based, but software is becoming an essential component. One basic observation about efficient algorithms is that for problems admitting an efficient parallel solution (counting is a great example), the parallel algorithm is generally more efficient, because energy use is typically superlinear in clock speed. As an extreme example, the human brain which is deeply optimized by evolution for energy efficiency typically runs at at 100Hz or 100KHz.

   Although efficiency suggests parallel algorithms, this should not be done blindly. For example, in machine learning the evidence I’ve seen so far suggests that online learning (which is admittedly harder to parallelize) is substantially more efficient than batch style learning, implying that I expect online approaches to be more efficient than map-reduce based machine learning as is typically seen in the Mahout project.

   A substantial difficulty with parallel algorithms is the programming itself. In this regard, there is plenty of room for programming language work as well.