What does the L2 or Euclidean norm mean?

Here’s a quick tutorial on the L2 or Euclidean norm.

First of all, the terminology is not clear. So let’s start with that.

Many equivalent names

All these names mean the same thing:
Euclidean norm == Euclidean length == L2 norm == L2 distance == l^2 norm

Although they are often used interchangable, we will use the phrase “L2 norm” here.

Many equivalent symbols

Now also note that the symbol for the L2 norm is not always the same.

Let’s say we have a vector, \vec{a} = [3,1,4,3,1].
Continue reading “What does the L2 or Euclidean norm mean?”

Theano – stack smashing error

I’ve been working on getting my laptop‘s Nvidia GPU working with Theano on Ubuntu 14.04. The whole process of getting the GPU to work has been a quite a learning experience… (but more on that later)

After installing Anaconda (which includes Theano!), I start Python from the Terminal:

$ python

Python starts up correctly. I then try to import the theano library…

>>> import theano

and Ubuntu freezes up 🙁

So I restart the machine and try again to run Python and import Theano, but get the following error message:

$ python
>>> import theano
*** stack smashing detected ***: python terminated
Aborted (core dumped)

Continue reading “Theano – stack smashing error”