Wednesday, December 26, 2007

Honey Bee Algorithm for Allocating Servers

I came across an interesting article in The Hindu (see the story from GaTech news; I couldn't find the link on The Hindu website) today which described work done by Sunil Nakrani and Craig Tovey, researchers in GaTech, on using a decentralized profit-aware load balancing algorithm for allocating servers for serving HTTP requests for multiple hosted services on the Web. The interesting, thing is that the algorithm is based on how Honey Bees in a bee-hive decide where to collect nectar from. I decided to take a look at the paper.

Essentially, the forager bees collect information about how profitable a particular nectar source and how much is the cost involved in collecting from that source (round trip time). Based on a composite score, they perform a waggle-dance which essentially indicates what is the value of performing foraging where they have been. The inactive foragers can thereafter figure out where to go look for nectar.

The researchers modeled it in the server space by having an advert-board, where servers post profits from serving a request and the time required to serve it. Thereafter, the other servers can choose which colony (or service) they wish to be a part of. Existing servers can also move to another colony based on a probability determined from a look-up table indexed by the ratio of their profits by the profits of their colony.

Their results indicate that they do quite well compared to optimal-omniscient strategy (which knows the pattern of all future web requests) and better than existing greedy and static assignment strategy. Shows that we still have a lot to learn from nature!

One thing that flummoxed me though was that the original paper seems to have been published way back in 2003 (see Tovey's publication page). I wonder why it got press publicity only now.

[The paper also cites a Harvard Business Review paper titled Swarm Intelligence: A whole New Way to Think About Business]

Wednesday, December 19, 2007

Fran Allen and the evolution of HPC

I had the good fortune of being able to listen to Fran Allen (IBM profile and Wikipedia entry) today. Fran pioneered a lot of work in compiler optimization and was awarded the Turing Award for her contribution to Computer Science in 2007. That makes her the first and only (till date) woman to have won the Turing Award, the highest honour in Computer Science.

It was inspiring listening to her talk about her adventures. She almost described the evolution of high performance computing, with the earliest IBM systems starting from Stretch, which was supposed to be 100X faster than the existing machines (but turned out to be only 50X faster) and was delivered to the National Security Agency. She also described some of failures she had been involved in (Stretch, since it was 2X slower than intended, and then the ACS project). What was interesting was that most of the basis of the pioneering work she described had its basis in the work she had done in these failed projects. The fact that failures are the foundations of mammoth successes is one message she clearly drove home with her optimistic outlook. She also described her work during the System 360 and the PowerPC projects.

Her appeal to computer science researchers and students was mainly about the programming models and architecture decisions revolving around multi-core, a buzz word most of us have been left confused and wondering about. This new revolution that promises to change the way we write software and exploit parallelism in our programs, is the biggest opportunity, as Fran put it!

What was also interesting was how we got to the lecture hall wading through mud in a construction site during the rain. Apparently, there are two conference halls at IISc -- one called JRD Tata and the other JN Tata. No wonder, we got to the wrong one and found that it as hosting a conference on Power Electronics. Note to self: make sure you always check the location properly before setting forth.

Other than that, have been lately busy with hacking Python for S60 (this is a brilliant idea-- having a platform agnostic scripting language!) to work on my phone and a Python based remote administration toolkit. Will post more about them soon!

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