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When Slide Rules Were Like Cellphones (hackaday.com)
szczys writes: Slide Rules and Pocket Protectors are the go-to items when making fun of old-time geeks. Forget the pocket protectors. Slide Rules were the first personal computers and a status symbol akin to what cellphones are today. Of course the general public wasn't attached to them, but engineers were. Before electronic calculators came around, everyone who needed to do some serious math owned Slide Rules. Stunningly easy to use and extremely effective, they have tick-marks placed on a logarithmic scale which makes complex multiplication, division, powers, etc. into visual calculations instead of mental ones.
New joke
Person A: "What's 0.1 + 0.2?"
Person B: "Let me check my computer, one sec... OK, looks like around 0.30000000000000004."
10.0 times 0.1 is hardly ever 1.0.
-- Kernighan and Plauger, The Elements of Programming Style
If it weren't for deadlines, nothing would be late.
Indeed, small difference of large numbers is only a problem for computers who brute force things. Quad precision is for wimps. Engineers had lots of tricks for re-writing equations so that the terms would naturally sum to a small number without large intermediates. I recall learning 4 different ways to write the quadratic formula that would avoid cases where b^2-4ac was the difference of large numbers or -b + sqrt(b^2-4ac) was the difference of large numbers. Since comuters I don't think I've ever seen that used. it's always coded with the textbook -b + sqrt(b^2-4ac). This is also why many eignenvalue algorithms give signular results in modern compuations. People don't spend the time to figure out how to avoid those precision level differences.
Some drink at the fountain of knowledge. Others just gargle.
This reminds me of something said by a very wise Professor I had in grad school. I "go back a ways" and I was in grad school just as electronic hand held calculators were beginning to appear, and slide rules were in their last days.
The Prof declared that the new calculators were an efficient way to calculate the wrong answer to a high degree of precision.
In other words, whether calculator, slide rule, computer, or whatever device --- none of them substitute for knowledge and judgment.