Category Archives: Facebook

The Art of NFL Ranking, the ELO Algorithm and FiveThirtyEight

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In this blog, I will focus on the NFL Ranking based on the ELO algorithm that Nate Silver’s FiveThirtyeight uses. The guys at 538 have done a good job.The ELO and NFL ranking was part of my workshop at the Global Big Data Conference this Sunday. The full presentation is in slideshare. 

ELO – the algorithm made famous by Facebook & depicted in the movie Social Network

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 Basic ELO

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The k-Factor is the main leverage point to customize the algorithm for different domains.

  • For example Chess has no notion of a season; Soccer,Football & Basket ball are dependent on seasons – teams change during different seasons
  • Chess has no score to consider except WIn,Lose or Draw; but ball games have scores that need to be accommodated
  • For Chess k=10; for soccer it varies from 20 to 60; 20 for friendly matches to 60 for World Cup Finals
  • As we will see later, NFL adjusts k with the Margin Of Victory Multiplier
  • NFL also adjusts k to weigh recent games more heavily, w/ exponential decay
  • There are also mechanisms for weighing playoffs higher than regular season games (We will see this in Basketball)

538’s take on ELO

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NFL 2014 Predicts & Results

The R program ELO-538.R is in Github

2014 Ranking Table

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To Do

  1. Exponential decay with more weight for recent games – later in the season
  2. Calculate the rankings from 1940 to present, draw graphs like this from 538

Facebook Infrastructure @ New Years Eve – A study in Scalability

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Another interesting article on how Facebook is preparing for the New Year’s Eve, this time from our own San Jose Mercury News By Mike Swift.

Interesting points:

  • New Year is one of the busiest times for social network sites as people post pictures & exchange best wishes

CEO Mark Zuckerberg has long been focused on having the digital horsepower to support unbridled growth — are a key reason behind the .. network’s success

  • It received > 1 B photo uploads during Haloween 2010
  • Since then Facebook added 200 million more members and so New Year Eve 2012 can see more than 1.5 B uploads !
  • My favorite quote from the article:

The primary reason Friendster died was because it couldn’t handle the volume of usage it had. … They (Mark,Dustin and Sean) always talked about not wanting to be ‘Friendstered,’ and they meant not being overwhelmed by excess usage that they hadn’t anticipated

  • The engineers at Facebook just finished a preflight checklist and are geared up for the scale
  • In terms of scale “Facebook now reaches 55 percent of the global Internet audience, according to Internet metrics firm comScore and accounts for one in every seven minutes spent online around the world.”
  • From a Big Data perspective, Facebook data has all the essential proprieties viz. Connected & Contextual in addition to large scale – Volume & Velocity (see my earlier blog on big data)
  • Facebook has the “Emergency Parachutes” which let the site degrade gracefully  (for example display smaller photos when the site is heavily loaded)
  • Their infrastructure instrumentation is legendary (for example, the MySQL talk here)

To manage Facebook’s data infrastructure, you kind of need to have this sense of amnesia. Nothing you learned or read about earlier in your career applies here …

 
And finally, Our New Year Wishes to all readers & well wishers of this blog