Improper Integrals with the HP-15C LE & CE

[J-F Garnier]

(11-15-2023 11:18 AM)Voldemar Wrote:  

(11-13-2023 05:30 PM)Namir Wrote:  intgeral of 1/sqrt(x) for x = 0 to 1 (exact is 2)
HP-15C CE gave:
Using FIX 5 calculator kept flashing "running" for quiite a while!

Tried HP 15C CE at FIX 6. Solved in less than 3 hours.
Result: 1,999999
Changing result to FIX 9: 1,999998943
How long it takes for FIX 9?

Using the HP 15c emulator, which is an accurate 15c LE simulation (including the bugs) but about 500x faster °:

FIX 5:   3s   1.99999    (1.999991771)
FIX 6:  23s  1.999999   (1.999998943)
FIX 7: 3min  1.9999997 (1.999999672)
FIX 8: >3h w/o result

So FIX 7 would take about one full day on the CE (several months on the original 15C !),

Don't try to use FIX 8 and FIX 9, it will not end before months on the CE and will for sure just kill the batteries.
It seems that the algorithm doesn't converge to the target accuracy, and never ends as discussed in this thread: Some questions about INTEG.

BTW, the HP emulator for Windows, despite its age (2012) is probably the fastest existing Nut CPU emulator (I mean: true microcode simulation, not functional HP-15c simulation).
I'm using it regularly and it's a bit surprising to me that it is not more widely used except by a handful of emulator-centric guys.
Maybe one reason is that it is not so trivial to find it in hpcalc.org (you have to look deeply in the torrent section). It would deserve a more visible place.
Note that I made (more than 10 years ago now) a 192-register version of it, that I released last year, leading to the 15c CE extended memory modes.

J-F

° : using a single core of my Ryzen5 machine with Win11.