HN user

ahalan

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www.theatlantic.com 13y ago

The Organization Kid

ahalan
2pts0
jwz.livejournal.com 13y ago

"I think you will all appreciate this person's commenting style"

ahalan
516pts88
www.quora.com 13y ago

What security measures do hackers use

ahalan
1pts1
research.microsoft.com 13y ago

Singularity OS: Rethinking the Software Stack

ahalan
7pts1
www.floridatoday.com 13y ago

Java's promise becomes a disaster

ahalan
4pts4
kickstarter.com 13y ago

Parallella: A Supercomputer For Everyone is Dying

ahalan
102pts64
www.foxnews.com 13y ago

Italian seismologists sentenced to 6 years for failing to predict earthquake

ahalan
1pts0
evanmiller.org 13y ago

In Praise of Small Data (2012)

ahalan
2pts0
www.math.mcgill.ca 13y ago

Why do we Sometimes get Nonsense-Correlations between Time-Series?

ahalan
15pts3
www.youtube.com 13y ago

Cosma Shalizi - Why Economics Needs Data Mining

ahalan
4pts0
blog.xkcd.com 13y ago

Urinal protocol vulnerability

ahalan
7pts0
www.python.org 13y ago

A style guide for Python code

ahalan
1pts0
community.topcoder.com 13y ago

TopCoder Contest: LoadBalance

ahalan
1pts0
www.rmetrics.org 13y ago

Real Time Trading in R (2009)

ahalan
1pts0
www.amazon.com 13y ago

Star Trek: The Next Generation: Technical Manual

ahalan
1pts0
www.sfgate.com 13y ago

Putting brakes on ride sharing apps

ahalan
1pts0
www.policymic.com 13y ago

Steve Wozniak Seeks Australian Citizenship

ahalan
2pts0
www.quora.com 13y ago

How does Akamai CDN work

ahalan
3pts0
www.seas.gwu.edu 13y ago

Matches and Recommendations

ahalan
3pts0
forwardthinking.pcmag.com 13y ago

High-End Server Chips Debut at Hot Chips '12

ahalan
1pts0
www.zdnet.com 13y ago

Curiosity Mars rover takes a drive

ahalan
1pts0
www.youtube.com 13y ago

Google tech talk: Running Large Graph Algorithms

ahalan
3pts0
queue.acm.org 13y ago

A Conversation with David Shaw

ahalan
4pts0
www.businessinsider.com 13y ago

Marissa Mayer Just Made Her Second Great Move As Yahoo CEO

ahalan
8pts0
atomicinsights.com 13y ago

Building Curiosity’s nuclear power source

ahalan
10pts0
irl.cs.ucla.edu 14y ago

On Memory Barriers

ahalan
1pts0
today.msnbc.msn.com 14y ago

How I created the algorithm that amazed Spider-Man

ahalan
3pts0
www.math.columbia.edu 14y ago

Higgs, Higgs, Higgs

ahalan
2pts0
www.math.uwaterloo.ca 14y ago

Applied Stochastic Processes (University of Waterloo)

ahalan
1pts0
cseweb.ucsd.edu 14y ago

MIT Lecture Notes on Cryptography

ahalan
49pts3
[dead] 14 years ago

take the job, Google on your resume is a very strong signal regardless of what you do, it will open lots of doors

>These processes include ignoring distractions to stay focused, switching attention willfully from one thing to another and holding information in mind

I'm trilingual and I can assure you it doesn't help with the ADD problem

Is this Hacker News or Institute for Noble Maidens?

That particular comment conveyed a valid point, it was done effectively and added to the discussion. I'm rather concerned that this site becomes more and more of an echo chamber as I see dozens of comments from different people that could be easily compressed into one.

MapReduce is applicable wherever you can partition the data and process each part independently of others.

I used Hadoop/Hbase for EEG time series analysis, looking for certain oscillation patterns (basically classic time-series classification) and it was an embarrassingly parallel problem:

Map:

1. Partition the data into fixed segments (either temporal, say 1hr chunks or location based, say 10x10 blocks of pixels). Alternatively you can use a 'sliding window' and extract features as you go. In some cases you can use symbolic representation/piecewise approximation to reduce dimensionality, as in iSax: http://www.cs.ucr.edu/~eamonn/iSAX/iSAX.html , "sketches" as described here: http://www.amazon.com/High-Performance-Discovery-Time-Techni... or some other time-series segmentation techniques: http://scholar.google.com/scholar?q=time+series+segmentation

2. Extract features for each segment (either linear statistics/moments or non-linear signatures: http://www.nbb.cornell.edu/neurobio/land/PROJECTS/Complexity... ). The most difficult part here has nothing to do with MapReduce but decide which features carry the most information. I found ID3 criterion helpful: http://en.wikipedia.org/wiki/ID3_algorithm, also see http://www.quora.com/Time-Series/What-are-some-time-series-c... and http://scholar.google.com/scholar?hl=en&as_sdt=0,33&...

Reduce:

3. Aggregate the results into a hash-table where the keys are segment' signatures/features/fingerprints, and the values are arrays of pointers to corresponding segments (Based on the size this table can either sit on a single machine, of be distributed on multiple hdfs nodes)

Essentially you do time-series clustering at the Reduce stage with each 'basket' in a hash-table containing a group of similar segments. It can be used as an index for similarity or range searches (for fast in-memory retrieval you can use HBase which sits on top of HDFS). You can also have multiple indices for different feature sets.

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The hard part is problem decomposition, i.e. dividing work into independent units, replacing one big nested loop/sigma on the entire dataset with smaller loops that can run in parallel on parts of the dataset, when you've done that, MapReduce is just a natural way to execute the job and aggregate the results.

on the exchange side - market data/trade/ack latencies can be microsec in the 50th percentile, single digit msec in the 90th, and double digit msec in the 99.99th, the variance can be significant and also change based on hr of the day and how well the exchange handles the load.

So even if you use customized, co-located hardware/FPGAs or even ASICs with the fastest interconnects and unlimited bandwidth and your engine responds in nanosec, still the message you get from/send to an exchange can sit there in a queue for something like eternity.