Found It!

I’ve been chasing a serious intermittent defect for five or six hours. This is almost unheard of, the way I work. But I finally figured it out. For the gory details of my mostly fruitless search, you could take a look at NO! A CRASH!. Here I’ll summarize what happened, what I did, what I think I’ve figured out, and then implement the fix. I am not sure even now whether I can write a test for the problem. It all started, doctor, when I ran the main with an experimental idea of randomizing cell selection during flood, and the program raised an exception and crashed. This is of course a serious problem, so I dropped the morning’s plan to find and fix the problem, and to figure out where my tests were so inadequate as to permit this. What followed was the longest debugging session I have had for very many years. There are probably a few reasons for that, perhaps some of them to my credit: My code is generally very simple, so crashes, if they occur, always occur and are therefore easy to…