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Showing posts from July, 2013

How I read a research paper

I can't tell you how you should read a research paper. Probably a different and customized style would work best for you.  But I can tell you how I read a research paper. And if you think some of the things below make sense, you can try them for yourself and see if they work for you as well.

So, how do I read a paper? The first answer that pops to my mind is "I fight with it". I strive to completely understand and "Grok" the paper by arguing with it. I resist to believe the claims in the paper at face value, I try to poke holes at it. I believe that the paper has to earn my trust, and I only accept the parts that I am obliged to accept.

My algorithm for reading a paper 0. Print the paper
1. Ask questions and argue with the paper
2. Write a review
3. Fight with the paper
4. Sleep on it and come back to it

Print the paperI like to physically touch the paper and handwrite and doodle on the paper. I have highlighter and different color pens ready with me, when I am…

Apps are selfish parasites! How can we get truly collaborative apps on smartphones?

While there has been good progress and wide availability of the devices (smartphones, tablets, sensors) to fulfill the ubiquitous computing vision, the-state-of-the-art in software and integration is lagging far behind. Consider DARPA's 2009 network grand challenge on the occasion of the 40th anniversary of the Internet. The challenge was to accurately find 10 weather balloons deployed in arbitrary locations of the U.S. within a day. There was an award of $40,000 for the team that would first report the locations of the 10 balloons accurately, and this challenge was solved within 9 hours. The winning team employed social networks and a multilevel incentive structure, but had to prepare, campaign, and publicize aggressively for an entire month before the challenge day.

This points to a big gap between the potential of the smartphones and the reality of the smartphone software today. Why are the existing apps so limited and person-centric? Why can we not have an app that is able to …

Ramblings on serializability

Here is a very raw/immature idea I have been toying with recently. I decided to write it down and share in order to get feedback about whether this is worth exploring further.

Serializability Serializability of reads and writes (sequential consistency) is an important feature in distributed systems. A significant application of serializability is in transaction processing in distributed databases (e.g., Spanner).

Paxos serialization versus serializability Paxos is a method for fault-tolerant state machine replication. In order to achieve fault-tolerant state machine replication, Paxos employs consensus to serialize operations at a leader and apply the operations at each replica in this exact serialized order (dictated by the leader).

While serialization is not an end in Paxos but rather a means, Paxos is seen nowadays as a defacto method for serialization rather than a method for fault-tolerant state machine replication. Maybe the ZooKeeper implementation of a Paxos-based lock-service…

Spanner: Google's Globally-Distributed Database

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The Spanner paper by Google (appeared in OSDI'12) is cryptic and hard to understand. When I first read it, I thought I understood the main idea, and that the benefit of TrueTime was to enable lock-free read-only transactions in Spanner. Then, I slowly realized things didn't check; it was possible to achieve lock-free read-only transactions without TrueTime as well. I did another read, and thought for some time, and had a better understanding of how TrueTime benefits Spanner, and how to improve its shortcomings.

I will first provide a summary of the Spanner work (borrowing sentences and figures from the Spanner paper), and then talk about what TrueTime is actually good for.

In a nutshell Spanner is Google's scalable, multi-version, globally-distributed, and synchronously-replicated database. Spanner supports non-blocking reads in the past, lock-free read-only transactions, and atomic schema changes. In order to support externally-consistent distributed transactions at glo…

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