It looks like you both agree that printing is not always good for debugging 
. Could you @gronki or @jwmwalrus please perhaps elaborate a little bit, like, in what scenarios, printing may not be a valid debugging method in Fortran? Thank you!
I actually always print the results when debugging the code 
PS.
You may reply in this thread How to fix "Heisenbug"? so we do not hijack this thread on this topic. Thanks!