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Originally Posted by: Jean Giraud  That's not a bug Radovan:
=>...For the free finding solutions, IC must be either 0 or 1
[1 to releive from "divide by zero"]<= ... {previous message}
Maybe you are not up to date vs Davide ?
Jean I was using SMath 0.98.6128 an NonlinerSolver 1.1.6099.14159 Regards, Ra |
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Originally Posted by: Davide Carpi Thank you guys, these examples are very useful to fix the bugs in this plugin  I'm working to a new version of the code, almost totally refactored. Looking at your examples seems there are several things to fix in my preprocessor; with some tweak, it is able to solve it. ![2016-10-24 18_27_07-SMath Studio - [FindRoot.sm_].png](/forum/resource.ashx?a=14941&b=2) now I just have to find some consistant way to make it working always  Davide, any progress about this plugin and its new version? Regards, Radovan |
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Originally Posted by: omorr Davide, any progress about this plugin and its new version?
Regards,
Radovan Hello Radovan! More or less, I'm trying to make it working on the numerical functions (those containing if/else, etc...), requires some more refactoring, I'll see if I can focus on this plugin in the coming weeks... |
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Originally Posted by: Jean Giraud Helo Jean, You should define f(x) not f(u). See the file, please. Was that your question?  Page1%20Unknown%20Solve-2-corr.sm (35kb) downloaded 57 time(s).Regards, Radovan |
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Hello Radovan, Example in context works fine for me. Integrator is now "scalar" 6179. It enables the Fourier Quantum double integral, though awfully slow. For N =31, CoC takes > 2hrs [Win 7 1.6 GHz]. ∫(x) comes from Maple. Jean Integral Curve Nuance.sm (27kb) downloaded 57 time(s).
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Hello SMath Community, need some help with findroot() function. I wrote a formula (biaxial bending in a column) to calculate unknown input loads based on known response. A key to practical use of the formula is to solve for unknown response based on known input loads (backwards of what formula does). When using findroot() for this purpose i run into error: FidRoot-CustomFormulaSolution.sm (538kb) downloaded 38 time(s). What am i doing wrong? Thanks!
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FindRoot, as well as other solvers of NS plugin, is not friend of eval, if/else or in general anything that requires a strict numerical evalution to be performed... that's a thing I'm working on (long overdue, I know...) |
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on 13/04/2018(UTC), on 15/04/2018(UTC)
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I don't know when these changes happened but my current observation of Findroot's behaviour seems to be different from earlier versions: - Just evaluate: displays result vector and executes embedded assignment
- Assign and evaluate in the same region: Error (symbolic evaluation reveals that the expression isn't executed but just stored as if it was inside line())
- Assign and evaluate in separate regions: displays result vector and executes embedded assignment upon display.
- Assign wrapped in eval() and evaluate in the same region: displays result vector and executes embedded assignment (here, eval() seems to be a friend of FindRoot())
In the sheet below I tried to demonstrate how to solve a system of equations using FindRoot() as alternative to Solve(). However, I am not sure how to explain the behaviour to the students. Should we generally avoid assignment with integrated evaluation for the time being? ![2018-12-12 00_06_28-SMath Studio - [Kerbformzahl Lochstab Biegung FKM.sm_].png](/forum/resource.ashx?a=28712&b=2) Kerbformzahl Lochstab Biegung FKM.sm (701kb) downloaded 34 time(s). |
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on 12/12/2018(UTC), on 12/12/2018(UTC)
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Originally Posted by: mkraska Should we generally avoid assignment with integrated evaluation for the time being? Yes, they should be avoided. There are several known issues while using implicit assignments, I plan to remove them when I'll have the possibility to commit a major update to this plugin. Moreover now SMath Studio supports multiple assignments by matrices on LHS, therefore it shouldn't be a big loss.  |
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Originally Posted by: Davide Carpi Originally Posted by: mkraska Should we generally avoid assignment with integrated evaluation for the time being? Yes, they should be avoided. There are several known issues while using implicit assignments, I plan to remove them when I'll have the possibility to commit a major update to this plugin. Moreover now SMath Studio supports multiple assignments by matrices on LHS, therefore it shouldn't be a big loss. Perhaps I wasn't clear enough. My example doesn't show any problem with embedded/implicit assignment (at least nothing obvious). What I mean is if you write an assignment with := and in the same region ask for display by = . This one seems to be a problem. Maybe, the two features are related, I don't know. If you drop integrated/implicit assignment, perhaps would be a good idea to return a set of boolean equations which can be used with at(), just like with Solve(). Then you can easily operate with multiple solutions without having to clear inbetween. |
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Originally Posted by: omorr Be my guest if you want to solve it A similar problem problem kept the Mathsoft Collaboratory [mostly Jean] busy for a while, solving for 22 variables. That was possible finally from Given/Find with infinitely many trial/error constraints. Given/Find Mathcad 8 Pro solves for 250 Given/Find Mathcad 11 solves for 400 but not of that nature Given/Find MCD 11 solves for 399 in for loop as the next call benefits of the previous estimates. That was done solving a DE of variable coefficients as functions [something like Frobenius] The Mathsoft 22 variables surely does not exist anymore in my old box as it was "secret" about what is was. Maybe the Originator said 'thaks' but not sure as commonly Done-Gone ! Yet, I don't completely understand the problem and its generation. Cheers Radovan ... Jean
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Originally Posted by: Jean Giraud Be my guest if you want to solve it Assuredly not a profitable guest ! I don't understand much in there. Primer38-doomed.sm (40kb) downloaded 33 time(s). Primer38-doomed_1.sm (45kb) downloaded 29 time(s).
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Originally Posted by: Jean Giraud Originally Posted by: Jean Giraud Be my guest if you want to solve it Assuredly not a profitable guest ! I don't understand much in there. Primer38-doomed.sm (40kb) downloaded 33 time(s). Primer38-doomed_1.sm (45kb) downloaded 29 time(s). Thank you Jeaan for your efforts, but I think we do not understand each other. This is not a fitting problem but finding roots of nonlinear system of equations  The solution was found in Mathcad - this post - and some other software but never in SMath Regards, Radovan |
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Originally Posted by: omorr
Here is the same problem solved in Mathcad
Regards,
Radovan
Hi. Can you show the guess values for x and y? And k before Find too. I get a very different k value. Remember that for numerical procedures, guess values are part of the solution, not of the problem. Thanks in advance. Best regards. Alvaro.
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Originally Posted by: Razonar Originally Posted by: omorr
Here is the same problem solved in Mathcad
Regards,
Radovan
Hi. Can you show the guess values for x and y? And k before Find too. I get a very different k value. Remember that for numerical procedures, guess values are part of the solution, not of the problem. Thanks in advance. Best regards. Alvaro. Thank you Alvaro for your interest in these problems. Here is the file once more. Primer38-doomed1.sm (32kb) downloaded 34 time(s). This is a system of nonlinear algebraic equations. If one takes a look at the calculation here it is obvious that any gradient algorithm for solving this system will fail. Therefore, some non-gradient method might solve this (direct solving or some minimization procedure). There are some functions in the NonlinearSolvers plugin, but unfortunately, there is no update of them for a long time and many of them do not work anymore. All of these years I mentioned that we need here some well tested and robust library incorporated in SMath regarding these problems. There are no other plugins which will address these problems (AFAIK) and I am not sure that will ever be any. Regards, Radovan Edited by user 11 February 2019 20:19:19(UTC)
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Originally Posted by: omorr This is a system of nonlinear algebraic equations. If one takes a look at the calculation here it is obvious that any gradient algorithm for solving this system will fail. Therefore, some non-gradient method might solve this (direct solving or some minimization procedure). There are some functions in the NonlinearSolvers plugin, but unfortunately, there is no update of them for a long time and many of them do not work anymore. All of these years I mentioned that we need here some well tested and robust library incorporated in SMath regarding these problems. There are no other plugins which will address these problems (AFAIK) and I am not sure that will ever be any. 1. You seem not happy of the result by plugging [x, y] from the other software. Did you enter enough decimals ? or that software is short of more ? 2. The Smath FindRoots is not robust in there but it can reproduce results from your source software with more decimals that you collected. 3. Presumably the software is Matlab ? 4. In short: for a fixed Phi, you are attempting to solve pairwise [x,y] as you scan over 'z'. Isn't true that any pairwise [x,y] will find a valid solution or closely ? Stated otherwise: the unique non trivial pair [x,y] is extremely sensitive to initials. That reminds me the Mathcad rootScanner that I designed for some extremely sensitive initials. But that one tool is only for one variable. Cheers Radovan ... Jean Primer38-doomed1[Solve paiWise].sm (11kb) downloaded 25 time(s).
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Originally Posted by: Jean Giraud Did you enterenough decimals ? 
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Hello Jean, The solution is from Mathcad (Given/Find) With an increased number of decimals.  Regards, Radovan |
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Originally Posted by: omorr Hello Jean,
The solution is from Mathcad (Given/Find)
With an increased number of decimals. That was my guess, no shame borrowing the hammer as needed. γRK(T,x):=eval(program) ... > 4 times faster. Cheers Radovan ... Jean
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