Whenever I type in syms x and run it, Matlab seems like it's being looped and I also can't stop it. How do I fix it?

I always need to use task manager to stop Matlab because pressing X doesn't shut it down.The problem just started today and I don't now why it keeps happening.

Answer 1

[Steven Lord]

Are you using Windows 10 Spring Creator Update 2018? If so see Bug Report 1755918.

[Khôi Nam Nguyen]

Yes,I think that will be the problem. Thank you for helping

[Jasper Chan]

First of all I just want to say that its ridiculous that the solution to such a fundamental problem is "pay for the newer version of matlab", but I digress.

I've updated to R2018a. I'm not quite sure what R2018a Update 1 means, but the 'Check for Updates' window lists both MATLAB and the Symbolic toolbox as up to date, yet my problem still persists.

>> syms x
Error using mupadmex
Internal error with symbolic engine. Quit and restart MATLAB.

Error in sym>tomupad (line 1219)
    S = mupadmex(numeric2cellstr(x));

Error in sym (line 211)
                S.s = tomupad(x);

Error in syms (line 201)
toDefine = sym(zeros(1, 0));

[Walter Roberson]

Install https://www.mathworks.com/downloads/web_downloads/download_update?release=R2018a&s_tid=ebrg_R2018a_1_1755918

[Dishank Mittal]

I was facing the same issue and trying to figure from 2 days. It worked finally. Thanks Walter! Cheers!

[Elena Manari]

Me too! Now it works. Thanks!

[Vinayak Vadlamani]

Steven, I tried the fix but it doesn't seem to work. Made the 2017b update. I run LabView in parallel on this system FYI.

System Info (ver)
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.3.0.713579 (R2017b)
MATLAB License Number: ••••••••
Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 17134)
Java Version: Java 1.8.0_121-b13 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode

[Steven Lord]

According to the output of the ver function that you posted you have not installed the update. I just installed the update in my installation of release R2017b and the first two lines of my ver output are:

>> ver
--------------------------------------------------
MATLAB Version: 9.3.0.867777 (R2017b) Update 7

[I trimmed some of the dashes in the divider, otherwise this post would have scroll bars.]

[Filipe Lima]

>> ver
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.4.0.813654 (R2018a)
MATLAB License Number: STUDENT
Operating System: Microsoft Windows 10 Pro Version 10.0 (Build 17134)
Java Version: Java 1.8.0_144-b01 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode

I have the latest version but the problem persists!

[Steven Lord]

You don't have the update installed. If you did, the MATLAB Version line would include "Update" and a number after the "(R2018a)".

Open the Bug Report link and click on the "R2018a Update 1" link in the Bug Report. [That now goes to a later update than Update 1, but the later updates include all the bug fixes from previous updates for that release.] Download and install the update.

[GAGANDEEP KAUR]

I have updated the version for R2018a but is still hving issue with the syms command , keep on running the code and not showing any result.Please if I could get some help

Here is the section I am having trouble with

syms a b c d e;
K1=zeros(1,5);K2=zeros(1,5);K3=zeros(1,5);K4=zeros(1,5);K5=zeros(1,5);
 for i=1:9
%calculating  mole fractions of ionic species
x1=[0.5096 0.5092 0.5087 0.4852 0.4847 0.4834 0.4804 0.4805 0.4803];
x2=[0.0963 0.0964 0.0965 0.1163 0.1161 0.1158 0.1275 0.1266 0.1253];
x3=[0.3941 0.3944 0.3948 0.3985 0.3992 0.4008 0.3921 0.3929 0.3943];   
T=[394.15 399.15 404.15 375.15 390.15 405.15 374.15 392.15 406.15]; 
%Equilibrium constant for reaction 1 (Solvation reaction)
K1(i)=exp((-8.549)+(6692/T(i)))
%Equilibrium constant for reaction 2(Ionization of water)
K2(i)=100
%Equilibrium constant for reaction 3(Dissociation of HI)
K3(i)=exp((16.93565)+((1250)/T(i))+(-2.575*log(T(i))))
%Equilibrium constant for reaction 4(Polyiodide formation a)
K4(i)=exp((-936.28)+((40216.27)/T(i))+(151.983*(log(T(i))))+(-0.1675*(T(i))))
%Equilibrium constant for reaction 5(Polyiodide formation b)
K5(i)=exp((1044.78)+(-45171.42/T(i))+(-165.20*log(T(i)))+(0.1511*(T(i))))

eqns=[((d*(c-e))/((x1(i)-a-b-c-d)^5)*(x2(i)-d-b-c))==K1(i),((a+b+c)*a)/((x1(i)-a-b-c-d)^2)==K2(i),((a+b+c)*(d+b))/((x1(i)-a-b-c-d)*(x2(i)-d-b-c-e))==K3(i),((a+b+c)*(c-e))/((x1(i)-a-b-c-d)^4*(x2(i)-d-b-c-e))==K4(i), (((e)*(x1(i)-a-b-c-d)^3)/((c-e)*(x3(i)-e)))==K5(i)];
S=solve(eqns,[a,b,c,d,e]);
S.a(S.a<0)=[];
S.b(S.b<0)=[];
S.c(S.c<0)=[];
S.d(S.d<0)=[];
S.e(S.e<0)=[];
S.a=double(S.a)
S.b=double(S.b)
S.c=double(S.c)
S.d=double(S.d)
S.e=double(S.e)
end

[Walter Roberson]

You should re-arrange.

... It will not help... but you should re-arrange.

syms a b c d e;

x1=[0.5096 0.5092 0.5087 0.4852 0.4847 0.4834 0.4804 0.4805 0.4803];
x2=[0.0963 0.0964 0.0965 0.1163 0.1161 0.1158 0.1275 0.1266 0.1253];
x3=[0.3941 0.3944 0.3948 0.3985 0.3992 0.4008 0.3921 0.3929 0.3943];   
T=[394.15 399.15 404.15 375.15 390.15 405.15 374.15 392.15 406.15];
N = length(x1);

K1 = zeros(1,N);
K2 = zeros(1,5);
K3 = zeros(1,N);
K4 = zeros(1,N);
K5 = zeros(1,N);

Sout = struct();

 for i=1:N
%calculating  mole fractions of ionic species

%Equilibrium constant for reaction 1 (Solvation reaction)
K1(i)=exp((-8.549)+(6692/T(i)));
%Equilibrium constant for reaction 2(Ionization of water)
K2(i)=100;
%Equilibrium constant for reaction 3(Dissociation of HI)
K3(i)=exp((16.93565)+((1250)/T(i))+(-2.575*log(T(i))));
%Equilibrium constant for reaction 4(Polyiodide formation a)
K4(i)=exp((-936.28)+((40216.27)/T(i))+(151.983*(log(T(i))))+(-0.1675*(T(i))));
%Equilibrium constant for reaction 5(Polyiodide formation b)
K5(i)=exp((1044.78)+(-45171.42/T(i))+(-165.20*log(T(i)))+(0.1511*(T(i))));

eqns=[((d*(c-e))/((x1(i)-a-b-c-d)^5)*(x2(i)-d-b-c))==K1(i),((a+b+c)*a)/((x1(i)-a-b-c-d)^2)==K2(i),((a+b+c)*(d+b))/((x1(i)-a-b-c-d)*(x2(i)-d-b-c-e))==K3(i),((a+b+c)*(c-e))/((x1(i)-a-b-c-d)^4*(x2(i)-d-b-c-e))==K4(i), (((e)*(x1(i)-a-b-c-d)^3)/((c-e)*(x3(i)-e)))==K5(i)];
S=vpasolve(eqns,[a,b,c,d,e]);
mask = S.a < 0 | S.b < 0 | S.c < 0 | S.d < 0 | S.e < 0;
S.a(mask)=[];
S.b(mask)=[];
S.c(mask)=[];
S.d(mask)=[];
S.e(mask)=[];
Sout(i).a=double(S.a);
Sout(i).b=double(S.b);
Sout(i).c=double(S.c);
Sout(i).d=double(S.d);
Sout(i).e=double(S.e);
disp(Sout(i))
end

[Walter Roberson]

My tests are suggesting that there might not be any positive solution.

[Walter Roberson]

For the first iteration, the closest I can find to a solution so far is

0.00917672806222852 234268.624175873 -4.132761874031 -234268.627565044 5.76374428893838

Yes, this does involve some very negative numbers. When I restrict to positive values, I do not come at all close to a solution.

[Walter Roberson]

It also appears that there might be fairly noticable round-off problems near that location.

[GAGANDEEP KAUR]

Thank you respected Walter Roberson for your effort and time. I may need to reform this system of equations.

[GAGANDEEP KAUR]

I have tried to run the code you suggested once .As you have found problem with negative values so I made it to run without this constraint and it still keep on running. On pausing it showed following message:

Operation terminated by user during mupadengine/evalin (line 123)

In mupadengine/feval (line 182)

[S,err] = evalin(engine,stmt,'message');

In sym/vpasolve (line 172)

sol = eng.feval('symobj::vpasolve',eqns,vars,X0);

In Equilibrium_constant (line 26)

S=vpasolve(eqns,[a,b,c,d,e]);

[Walter Roberson]

That is the expected message when you control-c to stop execution.

vpasolve is either not able to find an answer or takes a very long time to find an answer even when I tell it to start at a position that is pretty close to working (but not quite working.) My searches have not found any solution when I confine the values to +/- 1e6. And definitely not positive values only.

By the way, the equations have a singularity when c==e, leading to +/- infinity.

[GAGANDEEP KAUR]

Thank you for helping