Monthly Archives: January 2012

Twitter milestone

There are now over 100,000 followers across my various daily tip Twitter accounts. The three most popular are CompSciFact, AlgebraFact, and ProbFact. The newest account GrokEM has the least followers for now. Thank you everyone for following and for providing

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Wiggle paradox

Sometimes a graph looks wiggly because it’s actually quite flat. This isn’t much of a paradox; the resolution is quite simple. A graph may look wiggly because the scale is wrong. If the graph is flat, graphing software may automatically

Posted in Math

Rule of the last inch

From The First Circle by Alexander Solzhenitsyn: Now listen to the rule of the last inch. The realm of the last inch. The job is almost finished, the goal almost attained, everything possible seems to have been achieved, every difficulty

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Speeding up simulation with recurrence relation

Last week I wrote about how memoization reduced a simulation’s execution time from 300 hours down to 38 minutes. This weekend I came up with a different approach that reduces the time down to 21 minutes by taking advantage of

Posted in Computing

Twenty weeks down to twenty minutes

I had a simulation this week that I estimated would take 20 weeks to run. This estimate was based on too small a run. A more reliable estimate based on a longer run was 300 CPU hours, about two weeks

Posted in Computing

The most brutal man page

In The Linux Command Line, the author describes the bash man page* as “the most brutal man page of them all.” Many man pages are hard to read, but I think that the grand prize for difficulty has to go

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Review: The Linux Command Line

No Starch Press recently released The Linux Command Line: A Complete Introduction by William E. Shotts, Jr. True to its name, the book is about using Linux from command line. It’s not an encyclopedia of Linux. It doesn’t explain how

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Color-coded surgery

This is the most encouraging thing I’ve seen in cancer research in some time: a way to make tumors fluoresce. This allows surgeons to see tumor boundaries. From TED

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Boundary conditions are the hard part

What we call “differential equations” are usually not just differential equations. They also have associated initial conditions or boundary conditions. With ordinary differential equations (ODEs), the initial conditions are often an afterthought. First you find a full set of solutions,

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What do colleges sell?

Universities are starting to give away their content online, while they still charge tens of thousands of dollars a year to attend. Just what are they selling? Credentials, accountability, and feedback. Some people are asking why go to college when

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Grokking electricity

After I finished an electromagnetism course in college, I said that one day I’d go back and really understand the subject. Now I’m starting to do that. I want to understand theory and practical applications, from Maxwell’s equations to Radio

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Educational monoculture

I ran across the term “educational monoculture” this weekend. What a great phrase! Rather than write a long post, I’ll restrain myself and simply say that I’d like to hear more people talk about “educational monoculture.” Related post: Don’t standardize

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Oscillating Fibonacci ratios

You may know that ratios of consecutive Fibonacci numbers tend to the golden ratio in the limit. But do know how they tend to the limit? The ratio oscillates, one above the golden ratio, the next below, each getting closer.

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Rushing to see numbers

Scientific programmers and algebra students start out with analogous bad habits. Beginning algebra students rush to enter numbers into a calculator. They find it comforting to reduce expressions to floating point numbers as frequently as possible. This is understandable, but

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Funny and serious

G. K. Chesterton on being funny and being serious: Mr. McCabe thinks that I am not serious but only funny, because Mr. McCabe thinks that funny is the opposite of serious. Funny is the opposite of not funny, and of

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