rahinui

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1 years, 93 days

MaplePrimes Activity


These are replies submitted by rahinui

@Thomas Richard Great, thanks for verifying that it was a bug with Maple 2018; also, that's a great catch that it has to do with the hyperbolic representations! That's a clever workaround, thanks!

@tomleslie Great, thanks a lot for confirming that it was a bug, and also that it was fixed in Maple 2019. Also, I really appreciate the workaround for checking the solutions! That was a really clever way to deal with the issue, so I thank you for taking the time to show me a new trick.

Have a good one!

@tomleslie Great, thanks for the response! I agree, if I were expecting to get non-zero solutions, using lists would certainly be a better option. I used sets here because I expected these solutions to be correct, and its easier to check if the result is {0} rather than a list of the correct size. Regardless, that's good advice for the future, so thanks!

Checking the version reveals (I had just updated Maple and the Physics package earlier today after I first encountered the issue):

Maple 2018.2, X86 64 LINUX, Nov 16 2018, Build ID 1362973

2019, March 24, 15:56 hours, version in the MapleCloud: 340, version installed in this computer: 329.

Running your worksheet gives the same result (as a list):

[0, 0, 0, 0, 1/2*(2*phiL(0)*coth(d1)-n)/coth(d1), D(phiM)(0)+1/2*n]

Which shows its the final two equations are the issue. Again, I have no idea if this is relevant at all, but replacing phiL with phiM changes which variables are substituted correctly and which aren't:

[0, 0, 0, 0, 1/2*(2*phiM(0)*coth(d1)-n)/coth(d1), D(phiN)(0)+1/2*n]

Do you have any suggestions for what else I could try?

@Carl Love Unforunately, I must agree with you. While the workaround does resolve the problem in this specific scenario, its not really ideal. I've just submitted a bug report: hopefully it will be fixed soon (since it seems this is a relatively recent regression).

Thanks!

@Kitonum Cool, I didn't know about the empty symbol; that's a useful trick. Thanks for tip!

@dharr Ahh, good to know. So it seems that this is some sort of regression. Thanks for checking on that!

@Carl Love Wonderful, thank you very much for the informative explanation! I knew basically nothing about Maple's remember tables, so your overview is extremely helpful. It's good to know I can set the remember table type for procedures with an option like that.

Thank you very much!

Ah, I didn't know Maple used remember tables. That's googd to know. Thanks for pointing that out! And its good to know gc() is only discouraged for performance reasons; I figured it might have been deprecated for other stability issues.

For future reference, is there a good way to know that a command (like simplify) might be behaving differently because of remember tables? I was able to catch this because I knew the expression should evaluate to 0=0. However, in other cases, I'd like to rely on Maple for this?

Thanks, that really helps!

@acer Hmm, something is definitely weird there. Good catch. No idea why that's happening though...

@Preben Alsholm Ah, I hadn't checked that; that's a really good point. Thanks for highlighting that. I'm still a bit confused why the first one actually gives an incorrect result then. However, for my use-case, I think I can work-around this using assumptions.

Thank you so much for your help!

@Preben Alsholm Ahh, that makes sense; I hadn't even considered that. Thanks a lot, that really helps!

@Carl Love Thank you very much Carl! That's a very clever analysis and much faster than integrating every single term. I wouldn't have thought to eval(%, exp=1) to remove the exponential terms; that's a rather clever trick. Thanks for your help, this saves me lots of trouble.

Have a great one!

@Carl Love Ahh, .txt makes sense; thanks for the suggestions. Here's the file: MWE.txt, hopefully this time it works.

@Carl Love Sure, here's a maple worksheet: MWE.mw.

My original file was supposed to be a maple language file (.mpl). For
future reference, is there a proper way to upload .mpl files? It seems
that file type isn't supported here at mapleprimes (so I renamed it to
a .maple extension).

@vv True, in this case the assuming clause does nothing; it was simply to demonstrate the error. My (much) longer equation does require the assumption though. Nevertheless, I was able to rewrite my code to avoid this error, so it's not super pressing right now.

And thanks for the tip about restart; can't believe I never realized that.

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