This post reminded me of an old story. I was working as a student programming assistant at Georgia Tech in the 70s, when an unusual encounter occurred. A professor came into my office, acting a little agitated, when he dropped onto my desk, a large listing on greenbar (does anyone know what I am talking about?).
Then barely suppressing anger, he stated, "My da*n programs work!"
This being the first time I had ever heard this complaint (and the last time as it has turned out), I was a little confused myself.
Turns out, he had a couple programming examples of algorithms that he used to demonstrate numerically unstable or ill-conditioned problems in numerical analysis. When he used to run these on the university's computer system - they would not find an answer to the problem.
However, we had upgraded to a new system And his programs "worked", giving the correct answer every time. The upgrade went to a 64 bit processor and the increased word length prevented the round-off errors that had caused his algorithm to fail previously.
Happily, I taught him how to define his variables as single-precision instead of using the default precision, and his programs stopped working again!
Then barely suppressing anger, he stated, "My da*n programs work!"
This being the first time I had ever heard this complaint (and the last time as it has turned out), I was a little confused myself.
Turns out, he had a couple programming examples of algorithms that he used to demonstrate numerically unstable or ill-conditioned problems in numerical analysis. When he used to run these on the university's computer system - they would not find an answer to the problem.
However, we had upgraded to a new system And his programs "worked", giving the correct answer every time. The upgrade went to a 64 bit processor and the increased word length prevented the round-off errors that had caused his algorithm to fail previously.
Happily, I taught him how to define his variables as single-precision instead of using the default precision, and his programs stopped working again!
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