fix: make bubblesort.py compatible with python3

[jglathe]

chore: amend the comments in threadtesttool for clarity

[jglathe]

Hi Gary,

I found your repo through the Jetson nano review. Tried out the examples, and yes, the A57 cores are quite snappy. Compared to 2 other available machines, the results are:

time ./threadtesttool 100000000

AMD Ryzen 7-1700 2:47 for 8 real cores (gets really slow with 16, on Win10 in msys2)
Jetson Nano 3:50
AMD Phenom II X4 940 5:34 for 4 cores

Which is impressive in itself. All compiled with gcc.

Along the way I have found some minor changes to be necessary for bubblesort.py and some comment clarifications for threadtesttool.c.

with best regards

Jens