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Posts Tagged ‘mathematics

How large is a Two-Pizza Team? #scrum #xp

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After reading about 2 pizza teams in Wired UK 03.12, I read that the comment came from Werner Vogels, the Amazon CTO. He says prefers two-pizza teams; “technology teams working on a given project typically can be fed by no more than two pizzas—usually eight or fewer people.” This makes no sense to me, and I’m sure you may find the same.

I can easily eat a 13″ pizza at one sitting. A 13″ pizza has an area of approximately 856.3 cm2, the largest size that Dominos Pizza makes is 16″ with an area of approximately 1297 cm2. This means that I would be full at approximately 66% of the 16″ pizza, when I split it evenly the pizza only feeds two and leaves us both a little hungry.

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How does Vogels think he can feed up to 8 people with 2 pizzas?

Image source: VirtualErn


Written by Daniël W. Crompton (webhat)

March 8, 2012 at 7:07 pm

Just Finished Reading: The Quants #books #risk #economy

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I had heard of The Quants and wanted to buy it, after my father and I discussed how it was that all this money disappeared during the credit crisis I thought it might be wise to get an in depth view of the “China syndrome hedge fund catastrophe.” This is more than just a review of the book.

The first thing that I noticed were the multiple references to Ed Thorpe’s “Beat the Dealer”, a book on card counting Black Jack using a Hi-Lo method, and “Liar’s Poker“. Both books are on my bookshelf. Liar’s Poker highlights the years 1985-1987 as a trader at Salomon Brothers. There is some overlap between the characters of the book, such as John Meriwether who famously was challenged to a game of liar’s poker for 1 million dollars and replied: “If we’re going to play for those kind of numbers, I’d rather play for real money. Ten million dollars. No tears.”

The book reminded me of playing the computer game “Capitalism” when I was 16 in which I would game the system by creating a company which produced a little profit and initially plowing that profit into buying companies by hostile takeovers on the mini stock market and then avoid the system creating more AI companies – it had a fixed number of AI companies and mergers would cause new AI companies to be created – by buying a controlling interest in the AI companies and forcing them to turn out high dividends until all the AI companies in the stock market were under my control. And leave the computer AIs to tend to the companies and all their business while the dividends pushed my company’s profit into 12 digits.

The Quants is less of a narrative than Liar’s Poker, much of it is carefully crafted from multiple interviews with most of the players, books, magazines and newspaper articles. The tale of hedge fund managers and traders taking ever increasing risk just to earn the same amount that they did the previous year is and as it notes “Hedge fund managers who’ve seen big losses can be especially dangerous. Investors […] may become demanding and impatient. … [T]here can be a significant incentive to push the limits of the fund’s capacity to generate large gains […] If a big loss is no worse than a small loss or meager gains […] the temptation to jack up the leverage and roll the dice can be powerful.”

Even the glaring warning of Meriwether’s LTCM failure in 1998, like Daedalus’ warning to Icarus, it was ignored by most of the hedge funds. “By 1998, nearly every bond arbitrage desk and fixed-income hedge fund on Wall Street had copied LTCM’s trades.” They were leveraged up to their eyeballs, and while making huge debts of their own they traded with the debts of others, bonds, collateralized debt obligations and credit default swaps. Some hedge fund had leverages of 30 to 1, which means they borrowed $30 for each dollar they had as an asset. “Coming into 2008, hedge funds were in control of $2 trillion.” And the banks they were borrowing from had leverages of at least 9 to 1, because of fractional-reserve banking, these same banks “… Morgan Stanley, Goldman Sachs, Citigroup, Lehman Brothers, Bear Stearns, and Deutsche Bank, […] were rapidly transforming from staid white-shoe bank companies into hot-rod hedge fund vehicles fixated on the fast buck…” These banks had “… trillions more in leverage that juiced their returns like anabolic steroids.”

And it wasn’t just the banks, insurance companies go into the action too. These insurance companies insured the credit default swaps, “[i]f the value of the underlying asset insured by the swaps declined for whatever reason, the protection provider […] would have to put up more collateral, since the risk of default was higher.”

The light at the end of the tunnel is an oncoming train.
Wall Street proverb

“… [T]here were legitimate concerns that as computer-driven trading reached unfathomable speeds, danger lurked. Many of these computer-driven funds were gravitating to a new breed of stock exchange called ‘dark pools’—secretive, computerized trading networks that match buy and sell orders for blocks of stocks in the frictionless ether of cyberspace. … In these invisible electronic pools, vast sums change hands beyond the eyes of regulators. While efforts were afoot to push the murky world of derivatives trading into the light of day, stock trading was sliding rapidly into the shadows.”


“The findings of behavioral finance .. had shown time and again that people don’t always make optimal choices when it comes to money […] [N]euroeconomics, was delving into the hardwiring of the brain to investigate why people often make decisions that aren’t rational […] Evidence was emerging that certain parts of the brain are subject to a ‘money illusion’ that blinds people to the impact of future events, such as the effect of inflation on the present value of cash—or the possibility of a speculative bubble bursting.”

To me it also looks like they were and still are blinded to money. Two great reads for the weekend.

Image source: Amazon

Written by Daniël W. Crompton (webhat)

September 2, 2011 at 11:52 am

Just Finished Reading “The Code Book” #books

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I received The Code Book: The Secret History of Codes and Code-breaking as a present sometime ago. I had a love/hate relationship with cryptography and mathematics. I read this book when I got it, but re-reading it now was valuable.

It covers Fermat, Alice and Bob and goes on to quantum cryptography and quantum computing.

An interesting read.

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Written by Daniël W. Crompton (webhat)

March 30, 2009 at 7:38 pm

Just Finished Reading “Mathematics for Engineers and Scientists” #books

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I bought Mathematics for Engineers and Scientists for €10, the Amazon list price is $66.55.

I know mathematics, but when it comes to mathematic notation I’m lost. So I used this book as the teaching tool this is, it goes from simple addition and sets to differential equations and Fourier. I learned things I will probably never use, and some things I applied immediately. Now I can read an analysis on cryptography without needing to refer to the cheat sheet … very often. 🙂

Need to brush up or learn mathematics skills, this is absolutely the book for you!

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Written by Daniël W. Crompton (webhat)

March 25, 2009 at 7:07 pm

Posted in books, pki, school, science

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