This note relates to Windows Live Mail version 2009 (Build 14.0.8117.0416) running in Windows XP.

I found it impossible to export or copy ‘n’ paste the Safe Senders the addresses from Tools->Safety Options in my Windows Live Mail. I wanted to do this to import the list to the server-based Junk Mail filter provided by my email host.

A bit of digging about in the registry exposed the location of the Safe Senders list as

[HKEY_CURRENT_USER\Software\Microsoft\Windows Live Mail\PerPassportSettings\0\Junk Mail\Safe Senders List]

Unfortunately each address is saved in a separate registry subkey, so a bit of text manipulation is required after exporting the above Registry key to a .REG file. I used Edit-Plus to sort the file, strip out the non-pertinent stuff and perform a find-and-replace on the lines containing the email addresses, which are of the format

"Exception"="goodfriend@gmail.com"

a = 2 (n – R)

I always like a good real-world application of mathematics, in this case algebra.

The question

If you’re organising a knockout tournament for something and the number of players or teams is not a neat power of two, how many players have to be drawn in round 1, so that round 2 is a neat power of two? I figured this out by solving this pair of equations:

a + b = n
0.5a + b = R

where a is the number of players to be drawn in round 1, b is the remainder of players to be drawn in round 2, n is the total no. of players and R is the largest power of two less than or equal to n.

Solving the equations

0.5a + (n-a) = R
a + 2n - 2a = 2R
2n - a = 2R
a = 2n - 2R
a = 2(n - R)

An example

91 players enter our tournament, how many must be drawn in round 1?
n = 91, R = 64
a = 2 x (91 - 64)
a = 54
So we draw 54 players in round 1, which produces 27 winners to meet the remaining 37 players in round 2.

I have repeated the sampling of Twitter’s “sprinkler hose” that I carried out in April 2010. The data suggests that less than 10% of Twitter users are using twitter.com to interact with Twitter. The sample is based on 116,293 tweets captured between 4pm and 5pm BST on 11 Sep 2011. Continue reading “Top 100 twitter clients”