[petsc-users] PETSc on unstructured meshes / Sieve

[Marek Schmitt]

I would like to experiment with PETSc for learning FVM on unstructured grids. I get the impression that PETSc is primarily developed for structured grids with cartesian topology, is this true?

Pylith and Fenics seem to use Sieve for unstructured grids. Is Sieve part of PETSc?
Why is it so much hidden? The very silent sieve-dev mailing list exists since four years, but there is a recent post:
"2) Unstructured meshes. This is not well-documented. There is a tutorial presentation and a repository of code for it. A few people have used this, but it is nowhere near the level of clarity and robustness that the rest of PETSc has." (from http://lists.mcs.anl.gov/pipermail/sieve-dev/2010-October/000098.html)
Is the sieve-dev list about a different sieve than what is used by Pylith and Fenics?

There is a PETSc FAQ "Do you have examples of doing unstructured grid finite element computations (FEM) with PETSc?". It mentions Sieve but no further links or documentation.

Is the directory petsc-3.1-p8/include/sieve all that is needed to work with Sieve? Or are these only header files, and I have to link to the Sieve library from somewhere else (then where can I find Sieve)?

Please shine some light into the mysterious Sieve.
Marek