Solutiont o CG solver
Test works fine :)
Tidy up
Set up bigger coefficient matrix
Doing b vector too
Initial guess
Add norm to solution (should have been there a while ago)
Use norm of 1e-8
Run it through the bigger example
Now I'm building the fluid states. You can see here by running ./fluid_states.py that I have a load of fluid surrounded by solid!
OK! The matrix set up should be OK now. We need to plug it into the CG routine
OK - I have set up a really super-simple problem here.

All fluid in the centre with solids at the boundaries. The b vector is just a constant. Should be a pretty easy poisson problem...?
Aha ! A is singular. Hmm....
Ok - got a solvable problem finally....
The matrix is solving just fine. I can't get the A matrix to be correct when there are solid boundaries though...really not sure why this is.

Run ./fluid_states.py to see it rock and roll!
Fixed a couple of problems
Move into new folder and update the README