Easy way to install gcc-4.6 on Ubuntu 10.04

sudo apt-add-repository ppa:ubuntu-toolchain-r/test/ubuntu
sudo apt-get update
sudo apt-get install gcc-4.6
sudo apt-get install g++-4.6


From here. The alternative is to download gcc sources and install like this. 

svn: making trunk identical to a branch

So, I created a branch, made changes within the branch over a period and periodically kept merging from trunk into the branch. 

Now I want to make the trunk identical to the branch. The best approach for this is as described at http://stackoverflow.com/a/1008805/19501, namely use the three-way merge option:

...you want to merge "FROM trunk@HEAD TO branch@HEAD" with the working copy pointing to trunk. In essence:
"Give me all the changes I'd need to make trunk identical to branch".

Copy one sparse matrix into another in Python

Copying Xf into features. In this case, Xf is a scipy.sparse.csr_matrix and features is a dok_matrix.

        nz_indices = Xf.nonzero()
        for ix, jx in zip(nz_indices[0], nz_indices[1]):
            features[ix, jx] = Xf[ix, jx]

Notes: 

1. When I checked, the assignment of a 0 to an element of a dok_matrix resulted in a crash. So 0 assignments have to be avoided.