spack load --dependencies petsc@3.12.1
make -B ex1 &> ex1_make_3_12_1
mpirun -np 16 ./ex1 &> ex1_log_3_12_1

spack unload petsc@3.12.1
spack load --dependencies petsc@3.11.1
make -B ex1 &> ex1_make_3_11_1
mpirun -np 16 ./ex1 &> ex1_log_3_11_1

spack unload petsc@3.11.1
spack load --dependencies petsc@3.12.1
make -B ex2 &> ex2_make_3_12_1
mpirun -np 16 ./ex2 &> ex2_log_3_12_1

spack unload petsc@3.12.1
spack load --dependencies petsc@3.11.1
make -B ex2 &> ex2_make_3_11_1
mpirun -np 16 ./ex2 &> ex2_log_3_11_1