ezyang’s blog

the arc of software bends towards understanding

March, 2012

Reduce Ubuntu latency by disabling mDNS

This is a very quick and easy fix that has made latency on Ubuntu servers I maintain go from three to four seconds to instantaneous. If you've noticed that you have high latency on ssh or scp (or even other software like remctl), and you have control over your server, try this on the server: […]

  • March 24, 2012

Visit month: Princeton

If you haven't noticed, these are coming in the order of the visit days. Whereas the weather at UPenn was nice and sunny, the NJ Transit dinghy rolled into a very misty Princeton. Fortunately, I had properly registered for this visit day, so the hotel was in order. I was a bit early, so I […]

  • March 20, 2012

Is it better to teach formalism or intuition?

Note: this is not a discussion of Hilbert's formalism versus Brouwer's intuitionism; I'm using formalism and intuition in a more loose sense, where formalism represents symbols and formal systems which we use to rigorously define arguments (though not logic: a sliding scale of rigor is allowed here), while intuition represents a hand-wavy argument, the mental […]

  • March 18, 2012

Visit month: University of Pennsylvania

I'm hoping that this will be the beginning of a series of posts describing all of the visit days/open houses that I attended over the past month. Most of the information is being sucked out of the notes I took during the visits, so it's very stream of consciousness style. It's kind of personal, and […]

  • March 16, 2012

You could have invented fractional cascading

Suppose that you have k sorted arrays, each of size n. You would like to search for single element in each of the k arrays (or its predecessor, if it doesn't exist). Obviously you can binary search each array individually, resulting in a runtime. But we might think we can do better that: after all, […]

  • March 5, 2012