Raven Zachary, über-connector, has launched a nifty new site: portlandonfire.com that is profiling one Portlander a day. I’d like to know what his secret energy source is.

If you’d like to know my secret foibles, check it out — I’m featured today.

I’m tired of creating HTML attribution markup and style by hand every time I drop a Flickr photo into a post. I noticed the Yahoo Shortcut Plugin purports to address this issue. So I ended my procrastination and upgraded to WordPress 2.3.2 and installed the plugin. And here we are (see the image to the left)

Convincing the Yahoo Shortcuts Plugin to fetch the actual image of interest wasn’t as easy as I’d like but it’s clearly doable. I found the image using colrpickr, then navigated to the image and then entered the title of the image in the Yahoo Shortcut Plugin’s “Review This Post” view. The plugin found the image and allowed me to then add the image to my post.

Now wouldn’t it be the bomb if krazydad could integrate his colrpickr directly with the Yahoo thingie and save us all the steps?

Quickie findings: the in-development Ruby 1.9 VM performed best — beating 1.8.6 by a factor of two. For the numbers (comparing 1.8.6, 1.9 pre-release, and Rubinius pre-release) have a look at the spreadsheet and chart over on Google Docs. Also of note: the Ruby solution did beat the four minute time limit for N=10MM given in the problem statement. This was on random input. Worst-case performance would not be as good.

It makes me happy that the Ruby solution had adequate performance. Also it was interesting to see how the Ruby language fit for a problem you’d usually see done in LISP. I would have liked to have dynamic scope to do a cleaner implementation of @@largest_so_far. On the other hand, “memoization” is pretty natural in an OO language like Ruby — you create an instance (of Skyline) for each context and simply use instance variables to hold previous results.

update Nov 15, 2007: Reader Sumudu points out that version 5 neglects to reset the timer between pruning and non-pruning variations. Version 6 rectifies this error. With that change it’s apparent that the pruning has no positive effect. In fact non-pruning actually wins by a small amount for N=1 to N=100,000 on my MacBook Pro.

Harry the homeowner needs to remove the snow from his driveway. He has a snowblower that accomplishes this task well for normal snowfall. However, it can’t clear the high drifts of plow-wash when the city snowplows clear off the street in front of his house. This snow is piled too high, and compressed too much for the snowblower to work. So, Harry wants to clear the street in front of his driveway before the plow comes so that there is no snow for it to push into his driveway. Where, exactly, in the street should Harry clear? What variables determine the size and shape of the cleared area?

So I walk into class last Saturday and on the whiteboard is “The Twelve Days of Crossfit“. It’s like the song but you get to give yourself gifts — like handstands and clean-and-jerks. And you don’t wait a day between sets — you try to do the whole thing as fast as you can. Anyway I didn’t do the workout myself but I was intrigued by the sheer number of repetitions involved. Many of us have sung the song — but I wondered just how many “gifts” (repetitions) there were. A trip to Wolfram MathWorld (see Power Sums) and a little noodling yielded the following…

On each “day” (j) we perform j repetitions so the number of reps per day is:

And we do that for a number of days (N) so the total number of reps is:

But Wolfram MathWorld tells us that the inner sum can be reduced:

So the total from (2) becomes:

Which is the same as this:

We know (again from MathWorld) that:

Applying (6) and (3) to (5) gives the final solution to (2):

For N = 12 (Twelve Days of CrossFit) we perform a total of 364 reps! Thank goodness there aren’t 13 days or we’d have to do 454.

I’m sure my coach would be more impressed if I could do a proper squat. On the other hand, one must keep oneself entertained.