Geeklist #Hack4good 0.3 is almost over

2 hours of sleep, 1 cup of coffee and ∞ excitement! It looks like these ingredients are enough to survive a 10-hour hackathon!

First of all, let me fill in the gaps. I came to Dublin this morning to attend one of the greatest events of the globe; the Web Summit. The Web Summit is amazing, not only for the people it gathers and the talks it provides, but also because of the several side events it organizes; among them… Hackathon 🙂 .

#Hack4good 0.3 is a hackathon hosted by Geeklist in the Digital Skills Academy. As its name reveals, today we hack for good; all projects are proposed by humanitarian organizations and their aim is to serve people in need. Continue reading


From cloud computing to cloud diving

Everything pass in fast-forward from your mind; the moment you said let’s do it, the night you watched the first videos, the motivation, the “don’t do it” from family, the “you are crazy” from friends, the fear, the excitement, the doubt.

Questions; why? how? really? seriously?

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3 days before presenting

Correcting report… Check.

Preparing slides… Check.

Getting feedback from my supervisors in Telefónica… Check.

Getting feedback from my supervisor in UPC… Check.

Correcting slides… In Progress.

Making 3495736254 rehearsals… In Progress.

Anxious mode… ON!

“Let’s spread some Pregel and Giraph love and knowledge” mode… ON!

See you on Monday! 😉


4 days before delivering the Thesis Report

Right now, I should not be writing here, but only in my report :p But hey! I will be fast 😀

The day I was waiting for so long is approaching! 4 days till delivering the final thesis report. (teeth grinding, tears rolling, and a secret smile waits to give its huge finale to this 6-month performance)

I have so many words, definitions and numbers going around my head. And all this “jungle bubble” is taking structure in a form of sentences but getting restricted and limited in some lines of – somehow – academic writing.

I implemented 3 algorithms; all of them are Pregel-based, implemented on top of Giraph. They are iterative, vertex-centric and scalable.

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Run example in Giraph: PageRank

Latest Update: Check Questions: 4, 5, 7, 8 for changes. Instead of using the internal InputFormat and OutputFormat that SimplePageRankComputation has (which are currently buggy), I use others to make it work!

I’ve noticed an increase of the views for the Shortest Paths example,  so I decided to post my fairytale with PageRank as well. Please! Any suggestions, improvements, positive/negative feedback about these posts are more than welcome! I will respect you till the end of time 😉

So, let’s ask ourselves.

~~~~~ Q#1: What’s the PageRank problem?

Problem Description: Assign a weight to each node of a graph which represents its relative importance inside the graph. PageRank usually refers to a set of webpages, and tries to measure which ones are the most important in comparison with the rest from the set. The importance of a webpage is measured by the number of incoming links, i.e. references it receives from other webpages.

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[Paper Notes] Challenges in Parallel Graph Processing

While trying to write a possible introduction for my thesis report, I ended up reading an interesting paper listing Challenges in Parallel Graph Processing. According to this paper, graph problems have some characteristics that act as impediments to efficiently parallelize their solutions. These are (I list the same names given in the paper for their easier identification in the paper): Continue reading

Run Example in Giraph: Shortest Paths

When planning to run a code in Giraph, I ask myself some questions. When I answer to all my questions, I move to actually implement and run the code. (so I kinda discuss a lot with myself :p). Let’s have a look to this inner discussion – while running the Shortest Paths problem.

~~~~~ Q#1: What’s the Shortest Path problem?

Problem Description: Find the shortest path between 2 vertices in a graph, so that the sum of weights of the edges in the path is minimized. The example given in Giraph finds the shortest path from each vertex to the source-vertex.

~~~~~ Q#2: How can this be implemented in Giraph?

Think “Pregely”: Since in Pregel the same code is executed in all vertices at the same time, we need to think as we are a vertex. Continue reading