One question was: is DM42 the right tool? Can leave your program in memory, run it at one precision, switch precision, re-run, compare. Sort of related: It’s really cool to switch between 64bits and 128 bits on the wp34s. Handy! (BTW, I'm also using HP41C MLTI library on a couple of HP41CL's, not nearly so handy-glad someone developed it, but a little too complicated for my purposes.) Quick, efficient RPN entry, excellent precision. For quick checks, sanity checks, intermediate results, logic verifications, etc. Doing that anyway for the main solar system model. Changes the coding paradigm from “just-enter-the-equation” to “enter-long-sequence-of-function-calls.” Fine. (I’ve written all of my vector and tensor C++ libraries to use double doubles in hopes that the compilers will soon support additional precision.) Meanwhile, it's GMPL libraries. IEEE requires only that double doubles be no less precise than doubles. The g++ compilers I use on Linux and Raspberry PI support double double type variable definitions, but the double double types currently are no more precision than double types, 64 bits. – yes, it’s the best easy-to-use, program-in-an-instant, usually sufficiently accurate tool I know of. But for checking bits and pieces, intermediate results, etc. So one of the questions: is DM42 the right tool? Results for position vector will be Reg 04, 05 velocity vector Reg 06, 07. (I’ve computed the 10E10 and 10E11 results on other platforms, they'd take too long on the DM42.) program prompts for t max (for a single lunar orbit use 2416890) preload Reg 00 with # of iterations between display updates, say 100, or 1000.Ģ. Used as Tmax.ĭesired #of iterations Delta T Expected error in x component of radiusġ. Orbit period of moon is taken to be 2416890 sec. Sorry for the listing rather than a binary. In the complete model I’m building on a PC, I’m looking at errors in functions of order of magnitude jumps in delta time, so I’m doing the same thing here. RE this little test program, what it’s for: it’s a really stripped down simple Newtonian lunar orbit program meant to check on the errors in magnitudes (mostly of the radius vector between earth and moon) as a function of how fine the delta times used. (I Realize I'm way outside of normal use case envelope, but don't believe I'm misusing the product.) Approx 80 hours in, reset, loss of program, data. Started a second test at at 10E8 iterations. Executed completely in 84 minutes with expected results. Re-entered the Simple Orbit test program. HP41c(v,x) same program runs to completion (has run more iterations but requires weeks, AC power adapter precision not good enough). Post crash (reset) battery indicator shows all bars (near 100% charge).Ĭalc is on fan-cooled bench, never gets warm (don't think? thermal shutdown is at play)ĭM41x same program runs to completion (though precision is not good enough).įree 42s (IPad) same program has run up to 10 billion iterations, ie delta time = 0.000241689, (takes weeks and precision is not good enough). Then.eventually, it does reset, screen shows:Ĭalc is USB connected, known good cable, known good USB power supply. When calc dies, memory is lost so I don't know these times exactly.Īs program runs, I periodically monitor intermediate outputs-all values reasonable, no warnings, no indications of impending reset. What happens is program runs for several hours, usually up to accumulated time of maybe 1,500,000 simulated seconds, or about 650,000 iterations. In this instance, intention is to run 1 million iterations. (Program is 111 lines long, has some intermediate outputs position, velocity vectors stored in registers). Oribit period = 2,416,890 (s) (to use as max time)Įnd loop when accumulated time > orbital time Vinit = 1082 (m/s, velocity of moon at perigee) Rinit = 363,228,900 (meters, perigee of lunar orbit) I'm doing a numerical solution because this is part of a n-body problem solution for which, of course, there is no closed-form simple analytic solution. The program is a numerical solution to a lunar orbit. Some of these platforms are not appropriate due to limited precision, excessive calculation times. Other platforms that run the program fine include Free42s (on IPad), DM41x, wp34s, and HP41c. I have a program that runs fine on many RPN platforms but causes the DM42 to reset and lose memory after several hours.
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