source: pypar/FAQ @ 317

Q: If I broadcast a general structure how can I specify a
   suitable buffer for the receiving processes?

A: You must create something large enough to acccommodate the 
   structure (e.g a list conating blanks of sufficent size [' ']*N).
   The size of N must be estimated but it is OK to be larger   
   than the broadcasted structure.
   
   
Q: If I broadcast a general structure and specify a string as buffer
   I receve only garbage.
   
A: If you specify a string or a Numerical array as receive buffer
   you must use vanilla=True in the broadcast call. Otherwise the 
   receiving processes will think that they are receiving data with
   the type of the specified buffer.      

Q: Why do I have to specify a buffer in broadcast?
A: Issuing the command broadcast(x,  root=0) on all processors 
   will send the object x from processor 0 to x in every other
   processor.
   The same command is issued on all processors so x doubles as
   send buffer on root and receive buffer on the receiving processors.

   

INSTALLATION
--------------


Q: I installed the pypar package exactly as instructed, everything compiled 
   fine etc.  However, when I run python and enter `import pypar '  it says 
   that mpiext.c hasn't been compiled, even though there is an mpiext.so 
   sitting right in the directory.  I installed it with  --prefix=~. 

A: Because you are installing into your own home directory
   you need to update your PYTHONPATH so that python can find the installed modules.
   It should be set to ~/python by adding something like the following to 
   your startup script (here bash)

      export PYTHONPATH=.:$HOME/python:${PYTHONPATH} 


   This is not specific to pypar but general for all packages installed locally.