Wednesday, March 28, 2007

Multitasking or tunnel vision?

Judging from your feedback, my posts on concurrent programming, “Are hyperthreads good for you?” and “How many cores are good for you?” have been of interest to you, so here is a post on human multitasking.

We have all learned to appreciate multitasking, especially through threads or lightweight processes, because when a process idles waiting for the user to type the next key, RAM serving a fetch due to a cache miss, a program segment to be paged in, etc. the CPU can be used to process other tasks.

Even unrelated tasks benefit from multitasking. For example, instead of using an I/O driver to read and write from disk, a program can use the operating system’s virtual memory manager, which can collect a number of I/O requests from all threads and optimize them before doing a series of absolute disk accesses.

As you are a citizen of the blogosphere, I assume you are also doing quite a bit of multitasking, like maybe writing code while listening to a podcast, reading email, chatting with a colleague, and keeping an eye on a stock ticker in the corner. Are you getting the same benefits from multitasking as your computer does?

Not so, according to the article “Slow Down, Brave Multitasker, and Don’t Read This in Traffic” (subscription required) Steve Lohr wrote on 25 March 2007 in the Business section of the New York Times. Reviewing recent research at the universities of Michigan, Vanderbilt, Oxford (sponsored by Hewlett-Packard), Illinois, New York, and Boston, as well as research at Microsoft and MIT, Mr. Lohr concludes that in us humans context switching is so slow, that multitasking is not advised, except in rare situations. This is so also for people whom in the post on “Research in transition” I characterized as having a field dependent cognitive style. Such people are very good at parallel thinking, and masters for example in deconstruction (yes, Jacques Derrida is the philosopher of the blogosphere) or in esoteric Buddhism (yes, Kukai got there 1,200 years before Derrida). However, their parallel thought streams are all related or dependent.

When I consider the number of emails I receive each day, with the 15 minute context switching overhead reported by Mr. Lohr from Microsoft’s research, I would not get anything done at all. I am on email since 1980, and ever since retrieve my messages manually from the POP server only three times a day, when I get in at work, after lunch (OK, I multitask email and digestion, but do not use my brain for the latter), and before returning home.

Therefore, you cannot get instantaneous answers from me and your blog comments may take a while to show up online, but that is the why email is so much more convenient than the telephone—it is asynchronous. I do not use chatting, because in my view it is like walkie-talkies, not an efficient collaboration tool.

An interesting result quoted in the New York Times article is that younger people are not better at multitasking than older people. However, this is not due to the context switching overhead time, but to older people having a better tunnel vision, or capacity to focus on the task at hand: “The older people think more slowly, but they have a faster fluid intelligence, so they are better able to block out interruptions and choose what to focus on.”

To conclude, let me get back quickly to the comments to this blog. If you read it this month, you may have noticed a disparate variety of topics. The reason was for me to sound out were your interests lie. The only form of feedback I get are your comments, and this is the only information on which I can decide what to write on. Feel free to comment openly; if you use a screen name, I have no way to uncover who you are, nor can Corporate Communications, so I cannot even bribe somebody. The humans in the loop approve all comments not violating HP’s Standards of Business Conduct.

PS: as usual, since our software does not support links in comments, I am adding the links here