Author: regehr

  • Self-Checking Projects

    Matching students up with research projects is entertaining but difficult. The project has to be at the right level of difficulty, has to fit the student’s time frame, and has to interest the student. If grant money is going to be used to pay the student, the work has to fit into the funded project.…

  • White Baldy

    White Baldy, on the ridge between the Red Pine and White Pine drainages of Little Cottonwood Canyon in Utah’s Wasatch Range, is an infrequently visited 11,000′ mountain with no really easy routes: its east, west, and north ridges are all messes of bus-sized boulders. Bill and I decided that if we were ever going to…

  • INT_MIN % -1 = ?

    If you spend much time testing compilers, you’ll run into some strange phenomena even in apparently simple areas like computer arithmetic. For example John Cook wrote a post today explaining why IEEE floats have two different values of zero. Integer arithmetic is generally a lot simpler than floating point math, but it still contains a…

  • Why Take a Compiler Course?

    [Also see why take an OS course and why take an embedded systems course.] All good computer science departments offer a compilers course, but relatively few make it a required part of the undergraduate curriculum. This post answers the question: Why should you take this course, even if you never plan on writing a compiler?…

  • Good Fun and Bad Weather on Mount Baker

    The problem posed by this trip was to find a route that was interesting for my hiking buddy Bill while still being feasible for me. Bill is a seasoned mountaineer and has done some difficult climbs. I’m a strong hiker and feel comfortable on moderate snow slopes, but I haven’t done any technical mountaineering. Technical,…

  • Why Take an Operating Systems Course?

    [Also see why take a compilers course and why take an embedded systems course.] The other day, while having coffee with a colleague, I mentioned that I’ll be teaching OS in the fall. His area is far from computer systems and he asked me what’s the point of this class? What are the students supposed…

  • Flower Power

    The Wasatch Range peaks are 7000′ higher than the nearby Salt Lake Valley. This has many nice side effects but one of my favorites is that a wide variety of micro-climates is available within a small geographical region. In late Fall or early Spring it can be calmly drizzling in the city, but in the…

  • Compilers and Termination Revisited

    My earlier post C compilers Disprove Fermat’s Last Theorem generated a good amount of discussion both here and on Reddit.  Unfortunately, the discussion was riddled with misunderstandings. Some of this was because the topic is subtle, but some was my fault: the post was intended to be lightweight and I failed to explain the underlying…

  • Book Review: Street-Fighting Mathematics

    The Trinity test occurred on a calm morning.  Enrico Fermi, one of the observers, began dropping bits of paper about 40 seconds after the explosion; pieces in the air when the blast wave arrived were deflected by about 2.5 meters.  From this crude measurement, Fermi estimated the bomb’s yield to be ten kilotons; he was…

  • Book Review: Pale Fire

    Pale Fire is a 999-line poem written by John Shade.  It is also a novel by Vladimir Nabokov that contains an introduction by Charles Kinbote, the poem, and Kinbote’s extended commentary on the poem. On the surface, Pale Fire is straightforward.  The poem is a touching — but not, it would seem, terribly good —…