Floating point bug in Canon F-789SGA

[daschel]

(12-13-2014 06:17 PM)Peter Van Roy Wrote:  

(12-10-2014 06:35 AM)Gerald H Wrote:  You can accuse Canon of sloppy, unclear documentation but I don't think the claim of calc not fulfilling specs is warranted.

Independent of whatever the spec claims or not, it is a fact that this calculator has bugs in its basic floating point operations. Caveat emptor if you want to use this calculator for any important computations.

Hello, and my apologies if this thread has long been forgotten. But I have some findings which might change your perspective on this. I came across your post and tried your original test on a Canon F-792SGA, as well as with an HP 33s. And they both showed a loss of accuracy before their respective internal precision limits were reached.

The Canon (as you've already shown) loses precision with anything smaller than 1E-15, despite it's reputed 18-digit accuracy. This is not to be disputed; my results were exactly the same as yours. But it might surprise you that the HP 33s 'fails' your test with exponents lesser than -11. And this is in spite of its 15-digits of internal accuracy. It seems to me that you had singled out the Canon F-792SGA while other reputable (and pricier) calculators didn't fare any better, as they both fall short 3—5 digits of what would be expected, given their specs. Note: I asked the owner of an HP 35s to run the same test on his calculator and he notifed me of similar results.

To say the Canon isn't worthy of "serious" computations based your test is to impugn the functionality of other well-respected calculators; I seriously doubt you'll find too many mathematicians, engineers or statisticians who'd agree that the HP 33s isn't up to serious work—despite it falling short of anticipated results. The same courtesy must therefore be extended to the Canons. I suspect the width of temporary memory registers and legacy numerical libraries might all play a role in causing this. But the Canon F-792SGA is not to be faulted on this point, especially when compared with other "serious" calculators.

I hope you've found enjoyment with your F792SGA, or with another model that suits your requirements. Based on my experiment, I'm inclined to agree with the other poster who describes this as a documentation—but not a technical—problem.