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Posted by: peter

Kurt Grandis carried out an awesome Django vs .NET experiment at his company:

Almost two years ago I was in a rather unlikely situation in that I was running a software engineering department containing both a C# team and a Python team…It slowly dawned on me that I had a perfect test bed. Here we had two teams using different technology stacks within the same department…they shared the same development processes, project management tools, quality control measures, defect management processes. Everything was the same between these groups except for the technologies. Perfect! So like any good manager I turned my teams into unwitting guinea pigs.
With the result:
We found the average productivity of a single Django developer to be equivalent to the output generated by two C# ASP.NET developers. Given equal-sized teams, Django allowed our developers to be twice as productive as our ASP.NET team.

I just discovered Pyrit which takes a step ahead in attacking WPA-PSK and WPA2-PSK, the protocols that protect today’s public WIFI-airspace.

Pyrit‘s implementation allows to create massive databases, pre-computing part of the WPA/WPA2-PSK authentication phase in a space-time-tradeoff. The performance gain for real-world-attacks is in the range of three orders of magnitude which urges for re-consideration of the protocol’s security. Exploiting the computational power of Many-Core- and other platforms through ATI-Stream, Nvidia CUDA, OpenCL and VIA Padlock, it is currently by far the most powerful attack against one of the world’s most used security-protocols.

I continue to be amazed by the widely varied uses that these hardware graphics accelerators can be put to!

Posted by: peter
Today I had to knock up a quick web app to return the newest available file to an http based update client based on various criteria. Now this is a pretty typical scenario which almost any software company has to deal with once they have software deployed in the field that has some type of online update functionality built in so I’m not exactly blazing any trails here and didn’t expect to have any major problems.

However, as any developer knows, there is always something which puts a kink in what should have been a walk in the park. In this case it was the fact that our software versions don’t have a fixed number of digits after each decimal point (Something we have in common with many other projects, including the Linux kernel). This particular kink means that a table full of version numbers will not be returned in the order you expect when you use django‘s ORM order_by() clause (Which relies on the underlying PostgreSQL‘s ORDER BY clause). Given the list ‘1.0.0’, ‘1.0.10’, ‘1.10.0’, ‘1.0.9’ and told to sort in ascending order it will return ‘1.0.0’, ‘1.0.10’, ‘1.0.9’, ‘1.10.0’ instead of the expected ‘1.0.0’, ‘1.0.9’, ‘1.0.10’, ‘1.10.0’.

Python’s sorted() function also has the same problem:

>>> a = [‘1.0.0’, ‘1.0.10’, ‘1.10.0’, ‘1.0.9’]

>>> print sorted(a)
[‘1.0.0’, ‘1.0.10’, ‘1.0.9’, ‘1.10.0’]

This caused me to do quite a bit of digging around on google which pulled up a whole bunch of different ways to do what is apparently called a “natural sort” as apposed to an ascii based sort on a list. In the end I settled on the sort_nicely() function from the article Sorting for Humans : Natural Sort Order only to have it pointed out by some of the guys on #python that it could end up comparing int objects with string objects. Thanks to a little bit of coaching I finally ended up with the following naturallysorted() function which should be a drop in replacement for the python sorted() function:

def naturallysorted(L, reverse=False):
“”” Similar functionality to sorted() except it does a natural text sort
which is what humans expect when they see a filename list.
convert = lambda text: (”, int(text)) if text.isdigit() else (text, 0)
alphanum = lambda key: [ convert(c) for c in re.split(‘([0-9]+)’, key) ]
return sorted(L, key=alphanum, reverse=reverse)

As a comparison here is the same list processed by sorted() and naturallysorted():

>>> a = [‘1.0.0’, ‘1.0.10’, ‘1.10.0’, ‘1.0.9’]

>>> print sorted(a)
[‘1.0.0’, ‘1.0.10’, ‘1.0.9’, ‘1.10.0’]

>>> print sorted(a, reverse=True)
[‘1.10.0’, ‘1.0.9’, ‘1.0.10’, ‘1.0.0’]

>>> print naturallysorted(a)
[‘1.0.0’, ‘1.0.9’, ‘1.0.10’, ‘1.10.0’]

>>> print naturallysorted(a, reverse=True)
[‘1.10.0’, ‘1.0.10’, ‘1.0.9’, ‘1.0.0’]