Category: General

A while ago, I had the idea of always giving your customers a specially instrumented version of your product. The application would know what lines of code had been executed during your testing phase, and whenever the user ran a bit of code which hadn’t been tested pre-release, a dialog box would popup saying “Hey, you’re running code which we didn’t bother to test!”. How would you feel about doing that for your application?

Anyway, I stumbled across Guantanamo today which takes that one step further. It runs your unit tests, find any lines of code which haven’t been executed during the tests *and deletes them* from your source code. If they’re not being test, they’re not going allowed to exist. Heh, how cool is that?

I’ve always meant to write down a programming “stucklist”. It’s a list which you consult when you’re stuck. Maybe it tells you that you’re solving the wrong problem. Maybe it provides inspiration to fix the problem in a different way. Either way, when you’re under deadline pressure and your brain is dribbling out of your ears, a stucklist might just provide a way out. So, without further ado, here’s my initial stucklist:

Avail yourself of more facts
Can you solve a different problem?
Get out of the office and go for a walk.
How can else you make the problem go away without coding a fix for it?
Could you make the endusers avoid the problem area?
Go home and do something less boring instead.
Look at a more general version of the problem.
Or consider a more specific version of the problem.
Is it actually so bad not to fix the problem?
Fix one or more of the variables to simplify the problem
Grab someone, say “I’m a bit stuck” and throw some ideas around
Get someone else to fix it (evil bonus: they have to fix the fix too)
Can you buy in a solution, or spend money to make the problem go away?
Tell your manager that you’ve hit a problem and see if you can have more time, or redistribute work.
Get everyone else to workaround/avoid the problem area
Code a solution using a different style – recusive/iterative, stateful/pure, push/pull, table-based/computed.
How would you solve the problem if you had infinite memory or a super-fast CPU?
Can you put any supporting framework in place which makes the problem easier to fix?
Draw a diagram – I find it’s easier to walk through examples when you can look at something and point at it.
Assume that there’s a way to progress which doesn’t involve solve this problem – can you find it?

[Update: I’ve since found this page on the c2.com wiki which is similar]

X11R6.8 is set to be released soon, bringing some welcome technology improvements to X11 along with lots of pretty eye-candy.

Completely unrelatedly, for a while now I’ve been thinking about how to make a free-as-in-freedom map of Edinburgh. Not just the kind of map which you look at, but also a semantic map which computers could process. It would allow route-finding applications – not just finding routes for cars, but also for cyclists who want to avoid busy roads and hills. Another application could tell you where the nearest ATM or pub was. There are hundreds of useful applications, all of which need high-quality semantically-rich maps. But, as far as I can tell, in the UK all of the commonly used maps are derived from Ordnance Survey data which, despite being a sort-of public body, charge royalties for the data.

Now, on one hand, that’s quite reasonable because it takes a lot of effort to make good maps. But, on the other hand, I have a strong feeling that somehow this information ought to be in the public domain. Local people and companies could use this data in all sorts of ways. It ought to be a shared community resource.

So, I’m left wondering how I can use technology to map Edinburgh. Maybe a combination of a digital camera, GPS and a bicycle would be a good way of grabbing useful raw datapoints? Finding existing public domain map data would be a really useful start – satellite images and photos from aircraft. And there was a recent conference about open-source mapping tools. I think I need to do some basic reading about map-making, because quite honestly I don’t know where to start.

Now that the updated paper has been published, here is how to see the collisions for yourself:

1. Create messageA.pl, containing the following:

#!/usr/bin/perl
my $p = 
"d131dd02c5e6eec4693d9a0698aff95c2fcab58712467eab4004583eb8fb7f89" .
"55ad340609f4b30283e488832571415a085125e8f7cdc99fd91dbdf280373c5b" .
"d8823e3156348f5bae6dacd436c919c6dd53e2b487da03fd02396306d248cda0" .
"e99f33420f577ee8ce54b67080a80d1ec69821bcb6a8839396f9652b6ff72a70";
print pack("H*", $p);

2. Also create messageB.pl containing the following:

#!/usr/bin/perl
my $p = 
"d131dd02c5e6eec4693d9a0698aff95c2fcab50712467eab4004583eb8fb7f89" .
"55ad340609f4b30283e4888325f1415a085125e8f7cdc99fd91dbd7280373c5b" .
"d8823e3156348f5bae6dacd436c919c6dd53e23487da03fd02396306d248cda0" .
"e99f33420f577ee8ce54b67080280d1ec69821bcb6a8839396f965ab6ff72a70";
print pack("H*", $p);

3. Download md5.pl from here

4. Verify it works by doing “echo -n abc | md5.pl”. You should get 900150983cd24fb0d6963f7d28e17f72

5. Run “messageA.pl | md5.pl” and “messageB.pl | md5.pl” and you should get the same hash value (79054025255fb1a26e4bc422aef54eb4)

Today has been a somewhat unusual day in the crypto world. Some people have found collisions in some of the major hash algorithms used today. In itself, it’s interesting but not earthshaking – after all, by their very nature, hash functions contain collisions. But a method for finding collisions in some restricted case could well lead to more general methods, which would get exciting.

Being a cynic, I tried to verify the results in the paper using the funky MD5 in 8 lines of perl, but I couldn’t recreate their results. That was a bit unnerving. However, this page explains the discrepencies. Once the paper has been presented, presumably all will become clear.