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Showing posts from February, 2009

Breadth-First Search (BFS) & MapReduce

The Breadth-First Search (BFS) & MapReduce was roughly introduced from Distributed Computing Seminar. The graph is stored as a sparse matrix, finds shortest path using Map/Reduce as describe below:

Finding the Shortest Path: Intuition

- We can define the solution to this problem inductively:
- DistanceTo(startNode) = 0
- For all nodes n directly reachable from startNode, DistanceTo(n) = 1
- For all nodes n reachable from some other set of nodes S,
- DistanceTo(n) = 1 + min(DistanceTo(m), m ∈ S)


From Intuition to Algorithm

- A map task receives a node n as a key, and (D, points-to) as its value
- D is the distance to the node from the start
- points-to is a list of nodes reachable from n
∀p ∈ points-to, emit (p, D+1)
- Reduce task gathers possible distances to a given p
and selects the minimum one

According to above-mentioned idea, A map task receives a node n as a key, and (D, points-to) as its value. It means that an "input" is a set of all reachable path from 'sta…

Chinese Proverb - 兎死狗烹

Do you know '兎死狗烹'? It's a chinese proverb. In metaphrase, The man use hound to hunt rabbit but shoo the hound out onto the street after hunt rabbit. it means that when needed, it's grateful, but once unneedful, it's useless and abandoned.

Sexy or Intelligent Internet

It is better to be intelligent or sexy? For scientist is important to be intelligent. For model is important sexy appereance. For school professor is important to be intelligent. It is better to be intelligent or sexy to achieve the succes in relations to other people.

Then, the web application should be intelligent or sexy? IMO, It's same with above. A search engine should be intelligent enough to bring you the best information based on what you mean. A entertainment applications should be sexy, fresh, suggestive to provide more fun.

We can find that examples of these character from google.com and youtube.com.

What are the operating system most dominantly use in korea?

I noticed that someone visit my blog with this question - "what are the operating system most dominantly use in korea?". So I would like to answer that question.

In korea, Microsoft Windows (and IE browser) is still used on as many as 90 percent of China's 40 million PCs, because of most korea web-site (e.g. internet banking, game launch sites, multi-media site, ..., etc) requires Active-X on the high speed internet infra-. It was boom w/o special reason.

So, I think that not IE stuff (e.g., IPhone, Google Chrome, Safari, FireFox) didn't much appeal to korea market.

Google Chubby And Distributed Systems

Chubby is a sort of external lock-management server for reliability and availablity, and used to solve asynchronous consensus and other problems in distributed computing.

Building Chubby was an engineering effort required
to fill the needs mentioned above; it was not research.
We claim no new algorithms or techniques. The purpose
of this paper is to describe what we did and why, rather
than to advocate it. In the sections that follow, we de-
scribe Chubby’s design and implementation, and how it
has changed in the light of experience. We describe un-
expected ways in which Chubby has been used, and fea-
tures that proved to be mistakes. We omit details that are
covered elsewhere in the literature, such as the details of
a consensus protocol or an RPC system.

Papers are focused on their overall system architecture as they claimed. Click below to see more detail:

- The Chubby lock service for loosely-coupled distributed systems
- Paxos made live

Updated:
- There is a similar open source called zookee…

Google PowerMeter

Google PowerMeter, now in prototype, will receive information from utility smart meters and energy management devices and provide anyone who signs up access to her home electricity consumption right on her iGoogle homepage. The graph below shows how someone could use this information to figure out how much energy is used by different household activites.




Great, It represents a kind of ubiquitous computing system.

Naver storage hosting service, called 'N drive'

Naver internally work for online file sharing and storage service, called 'N drive' which is store large amounts of user files using OwFS (Ownership-based File System). I don't know exactly when it will open, But it's a clearly shows that NHN also started to deal with cloud-related problems.

FT: IBM Creates a Cloud Computing Division

by Timothy Prickett MorganYou know that Big Blue is getting serious about something when it creates a formal division to manage it. Last week, IBM announced that it was creating a cloud computing division just as it had also announced that key systems software would soon be available for deployment on Amazon's Elastic Compute Cloud (EC2).Technically speaking, Erich Clementi, who is currently IBM's vice president for strategy and who was formerly a general manager of the Business Systems division (which peddles gear to small and medium businesses) and the System z mainframe business, is now also general manager of Enterprise Initiatives, which is where the company is currently parking all of its cloud computing efforts. And instead of reporting up through Systems and Technology Group or Software Group or Global Services, like the other IBM groups do, this Enterprise Initiatives division reports directly up to IBM president, chief executive officer, and chairman, Sam Palmisano.A…

Cloud Computing?

Larry Ellison said that the computer industry is more fashion-driven than women's fashion and cloud computing is simply the latest fashion. And Richard Stallman, founder of the Free Software Foundation and creator of the computer operating system GNU, said that cloud computing was simply a trap aimed at forcing more people to buy into locked, proprietary systems that would cost them more and more over time.

Then, What do I think cloud computing is?
I agree with stallman in part that it's a really dangerous technology, But I think cloud computing is the realization of the earlier ideals of utility computing without the technical complexities or complicated deployment worries. Cloud competition has already started between the most global principal IT companies (e.g. google, y!, IBM, amazon, HP, facebook, ..., etc), netizens are already acclimatized on the cloud internet services. (at least in the korea)

Meanwhile back at the NHN, corp., they also took a conservative action (e.g. f…

Naver's takeover of Wingbus

The RealTravel of south korea, Wingbus which aggregates tour stories and photos of bloggers from Naver, Daum, ..., etc. has been take over by NHN, corp.

The venture competition seems a story from the old days.