X^Y on the Elektronika B319M

05242018, 10:22 PM
Post: #1




X^Y on the Elektronika B319M
The Elektronika B319M has a 3 level stack (x, y, z). It has an X^Y function that works as expected. The result is identical to pressing 'ln', '*', 'e^x'. What puzzles me is, that the later leves the z register intact an duplicates its contents into y (as expected), while the dedicated 'x^y' places ln10 in both z and y register. The manual says that z is lost, but I have no idea what ln10 might be used for in calculating x^y.
Any thoughts? Cheers, Harald 

05242018, 11:52 PM
Post: #2




RE: X^Y on the Elektronika B319M
That is very strange.
Perhaps work of Moose and Squirrel? 

05252018, 01:10 AM
Post: #3




RE: X^Y on the Elektronika B319M
Is meant to confuse!
Remember kids, "In a democracy, you get the government you deserve." 

08072018, 05:23 PM
Post: #4




RE: X^Y on the Elektronika B319M
The result of "x^y" differs slightly from the result of "ln"+"*"+"e^x" (unlike B321, B334!). E. g., 8  8 x^y gives 16777188, 8  8 ln * e^x gives 16777173. But the same operation with DECIMAL logarithms (8  8 lg *  10 ln * e^x) gives 16777188. Most probably it uses a similar algorithm, directly placing ln(10) in Z.


08082018, 07:07 AM
Post: #5




RE: X^Y on the Elektronika B319M
(08072018 05:23 PM)watchmaker Wrote: The result of "x^y" differs slightly from the result of "ln"+"*"+"e^x" (unlike B321, B334!). E. g., 8  8 x^y gives 16777188, 8  8 ln * e^x gives 16777173. But the same operation with DECIMAL logarithms (8  8 lg *  10 ln * e^x) gives 16777188. Most probably it uses a similar algorithm, directly placing ln(10) in Z. Thanks for the hint, that is interesting! So the result is a bit closer to the correct 16777216. I still wonder why you would make the calculation more complicated and loose a register for this minor improvement. But I guess that is what they must have done. Cheers, Harald 

08082018, 11:43 AM
Post: #6




RE: X^Y on the Elektronika B319M
(08072018 05:23 PM)watchmaker Wrote: The result of "x^y" differs slightly from the result of "ln"+"*"+"e^x" (unlike B321, B334!). E. g., 8  8 x^y gives 16777188, 8  8 ln * e^x gives 16777173. But the same operation with DECIMAL logarithms (8  8 lg *  10 ln * e^x) gives 16777188. Most probably it uses a similar algorithm, directly placing ln(10) in Z. Perhaps ln(10) is needed to reduce argument for exp(x), for speed and accuracy. ln(8 ^ 8) = 8 ln(8) = 16.63553233 = 7 ln(10) + 0.517436682 8^8 = 10^7 * exp(0.517436682) = 10^7 * 1.6777216 

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