Parallel debugging

[Daniel Underwood]

I'm programming a multithreaded scientific program using pthreads and
c++.  Currently The model is SMP, but may investigate MMP using MPI in
the future.  Can anyone suggest a good debugger and possibly an
associated GUI? (E.g., gdb and ddd.)

Along the same lines, are there any free solutions comparable in scope
and/or quality to the TotalView set of debugging tools?

TIA,
Daniel