Hi,

can you give more information about what you did to produce the error?

I can  give you more information. I have tried to simulate this simple example:
model daadd
  Real x;
equation
  1 = x - 1 - (x - 1) ^ 2 / 2 + (x - 1) ^ 3 / 3 - (x - 1) ^ 4 / 4;
end daadd;
And then I get this message:"Too few rows in data_2 matrix".

Look closer. You also got another error-message:

LOG_NLS        | warning     | nonlinear system 2 fails: at t=0 Debug more

|        | |     | | proper start-values for some of the following iteration variables might help

|        | |     | | [1] Real x(start=0, nominal=1)

assert        | debug     | Solving non-linear system failed at time=0.

For more information please use -lv LOG_NLS. Debug more

Simulation process exited with code 255

(Note that complex solutions are not solutions in Modelica; the equation should not be possible to solve)

No. I have another code:

LOG_NLS        | warning     | Error solving nonlinear system Nonlinear function (residualFunc5, size 1) at time 0 Debug more

stdout        | warning     | Error in initialization. Storing results and exiting.

Use -lv=LOG_INIT -w for more information.

Process crashed

Simulation process exited with code -1

sjoelund.se wrote:

(Note that complex solutions are not solutions in Modelica; the equation should not be possible to solve)

I didn't understand what do you want to say me.

Same thing. Just an older omc version. Exit code -1 is the same as 255 (because on Linux the exit code is an unsigned char).

Ascold wrote:

sjoelund.se wrote:

(Note that complex solutions are not solutions in Modelica; the equation should not be possible to solve)

I didn't understand what do you want to say me.

Your equation has four solutions; for example:
x = 0.5389-1.4934 i

Modelica Real numbers are not imaginary. So your model should be unsolvable. And OpenModelica says it was unable to find a solution; so it did the right thing telling you that.

sjoelund.se wrote:

Ascold wrote:

sjoelund.se wrote:

(Note that complex solutions are not solutions in Modelica; the equation should not be possible to solve)

I didn't understand what do you want to say me.

Your equation has four solutions; for example:
x = 0.5389-1.4934 i

Modelica Real numbers are not imaginary. So your model should be unsolvable. And OpenModelica says it was unable to find a solution; so it did the right thing telling you that.

Thanks for answer. It is correct. Please tell me more. If its true so why I cannot calculate this code ?
model   sjoelund.se
parameter Real tw1=32.1;
  parameter Real tw2=36.4;
Real tk2;
equation
  1=(tw2-tw1)/(2.3*log10((tk2-tw1)/(tk2-tw2)));
end sjoelund.se;
I have same errors..Dymola solves that code perfect and has no errors.

Probably because OpenModelica does not know the inverse of log10. If you give tk2 a start-value of 36.4, it finds the solution using a non-linear solver.

sjoelund.se wrote:

Probably because OpenModelica does not know the inverse of log10. If you give tk2 a start-value of 36.4, it finds the solution using a non-linear solver.

You are smart. Thanks for answer .Can I distract you, if I will have some question?

Usually someone will answer questions. I get email notification for all posts to these forums.

Hi Guys,

Saw your conversation and thought to jump in as I have the same issues.  Basically I am trying to solve the following equation :

model Test
  parameter  Real m(unit = "kg/s", min = 0) = 9.96720e-005;
  parameter Real Pdown(unit = "bar", min = 0) = 2.048153 - 0.6209;
  parameter Real Cd = 0.7;
  parameter Real D(unit = "m") = 0.0005588;
  parameter Real Tup(unit = "°C") = 20.5;
  parameter Real g(unit = "Dimensionless") = 1.401;
  parameter Real Rspecific(unit = "J/(kgK)") = 287.1;
  constant Real PI = 3.14159265;
 
  Real Pup ;
  Real Aorifice(unit = "m2");
   
equation
  Aorifice = PI * (D / 2) ^ 2;
  m = Cd * Aorifice * 100000 * Pup / sqrt(Tup + 273.15) * sqrt(g / Rspecific * 2 / (g - 1) * ((Pdown / Pup) ^ (2 / g) - (Pdown / Pup) ^ ((g + 1) / g)));
 
end Test;

However when I try to solve I get the following error message:

record SimulationResult
    resultFile = "",
    messages = "Simulation execution failed for model: Test
stdout            | warning | Non-Linear Solver try to handle a problem with a called assert.
stdout            | warning | While solving non-linear system an assertion failed.
|                 | |       | | The non-linear solver tries to solve the problem that could take some time.
|                 | |       | | It could help to provide better start-values for the iteration variables.
|                 | |       | | For more information simulate with -lv LOG_NLS
stdout            | warning | Non-Linear Solver try to handle a problem with a called assert.
stdout            | warning | While solving non-linear system an assertion failed.
|                 | |       | | The non-linear solver tries to solve the problem that could take some time.
|                 | |       | | It could help to provide better start-values for the iteration variables.
|                 | |       | | For more information simulate with -lv LOG_NLS
stdout            | warning | Error in initialization. Storing results and exiting.
|                 | |       | Use -lv=LOG_INIT -w for more information.
"
end SimulationResult;

Could you please help me how to overcome this issue?  I do not understand how to use the -lv=LOG_INIT -w command and what initial start values should I allocate to Pup

Thank you for the help