Solve block finds no solution

[Manfred_F]

I implemented a solve block, which worked with Prime6. Now with Prime7 it does not find a solution anymore. I reworked the problem using a simpler function to make it easier to understand and even this easy equation is not solved. Unluckily I have a new computer for some weeks, with a completely new installation and only have Prime7 installed.

Both versions of the solve block do not work. I know, that the equation could be solved easier, I just used the solve block for demonstration (see attached SolveBlock). In my application the function is much more complex and it worked with Prime6 (SolveBlock_original).

[terryhendicott]

Hi,

You need to make some definitions before the solve block.

See the comments in the file

[Manfred_F]

Hi Terry,

thanks for the help, but I cannot open the file. I'm using Prime7. Can you send me a screenshot or the file in Prime7 format?

[Manfred_F]

Hi Terry,

when you look into my example on the right side (Lower2). This did also not work. By the way you can use a function as a parameter, as it was done on the left side. In this case you can provide the function as a parameter to the solve block. As I said this worked with Prime6 as you can see in "SolveBlock_original"

[Werner_E]

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@terryhendicott wrote:

Hi,

You need to make some definitions before the solve block.

See the comments in the file

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No!! it should not be necessary to define f.err or Vth before the solve block because in the sheet provided by the OP both are provided as arguments of the solve block function "Lower".

But in your screenshot it looks like that defining the function argument Vth with an arbitrary value in front of the solve block seems to make it work OK. @Manfred_F  So this may be at least a work around to make the solve blocks work in the buggy version 7 - give it a try!
Furthermore I notice that the DeltaV after "find" is bold and upright (labelled as "Keyword" or "System"). Thats obviously no problem in Prime 6 but it may be worth a try to manually label it as "Variable" and see if it helps in Prime 7.

I am using Prime 6 and all I can do is to confirm that both solve block functions in the sheet provided by @Manfred_F  work OK in that version (see the screen shot below).

If I remember correct we already have seen some posts here in the forum indicating that the numeric algorithms seem to have been modified after version 6 of Prime and so calculations working in older versions are failing in Prime 7 (and maybe also in P8).

Perhaps someone using Prime 8 could report whether or not the two solve block functions in the OP's unmodified worksheet work OK after a recalculation. Chances are that the bug may have been already fixed in the current version.
If not, I would suggest reporting this bug to PTC support and hoping for the best...

Here the screenshot showing the results after a recalculation with Prime 6:

[DJNewman]

[Werner_E]

Thanks!

So it looks that either its a bug introduced in P7 and already fixed in P8 or that there is something faulty with the installation of @Manfred_F's P7.

[LucMeekes]

I opened the file with Prime 7, and saw no results.The Stop All Calculation and Calculate buttons were greyed out.

Then I pressed the Auto Calculation button and promptly got:

As well as the result for Lower2(50)=0.505.

Can't show here because the forum software is not helping by refusing to show pictures.

Anyway, is this what you hoped to get?

Success!
Luc

[Werner_E]

So this means that maybe the problem simply was that "Autocalc" was turned off !? 🙂

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Can't show here because the forum software is not helping by refusing to show pictures.

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So you are experiencing the incredible slow reaction of the forum software as well?
Actually the embedded pictures will show up sooner or later, but it takes a long time. Its like accessing Khoros using a stone age old 56k modem.

I already brought the problem to @Jaime_Lee 's attention by posting a note here

https://community.ptc.com/t5/Mathcad/Van-Roomen-s-problem/m-p/843290/highlight/true#M204117

and also sent her a PM with more details.
Since I had the same effect with another machine on a different network with a much snappier Internet connection, I was pretty sure that the problem was not on my end. However, I had been puzzled by the fact that no one else had complained of problems here yet.

[Manfred_F · Accepted solution]

Thank you all for helping.👍

Today I opened the file and it worked at once. Maybe I had no licence or whatever, but Prime was calculating without end showing the yellow circle for at least 15 minutes yesterday. I tried it several times yesterday with the same result. Also the original calculation now works.

For the future it would be good to get an error message or whatever in such a case.