[firedrake] value of PETSC_DIR used by activate?

It looks like I have found part of my confusion. I have now reinstalled firedrake with PETSC_DIR unset, so there is an old PETSc (i.e. 3.4.2) inside the firedrake directory. But if I run activate later it seems to use the value of PETSC_DIR at that time. This is my working explanation for why I get seg faults and why "gdb --args python3 MYSCRIPT.py" shows backtraces with the wrong PETSc (i.e. the 3.9 version I am using for other purposes). So it looks like I should do $ unset PETSC_DIR $ source firedrake/bin/activate every time I start firedrake? Is this the correct action if one has PETSC_DIR set? Ed -- Ed Bueler Dept of Math and Stat and Geophysical Institute University of Alaska Fairbanks Fairbanks, AK 99775-6660 301C Chapman