API Value for FMI 2

[SudeepGhoshIN]

Hi Team,

I have a requirement of passing start value for Measurment and Outputs in FMI2.0.
As part of this , I am trying to utilize fmi2_import_get_variable_has_start(fmi2_import_variable_t*) API to check if the variable contains start. But unfortunately, above mentioned API is not returning value , so I could not proceed further for retrieving the start value.

Though I am getting proper value for Calibration and Inport value while trying to read from Parameters and Inputs variable.

Many Thanks,
Sudeepp

[PeterMeisrimelModelon]

Hi SudeepGhoshIN,

you retrieve the start value via fmi2_import_get_real_variable_start, note that this will instead return the nominal if there is no start value, so you should still check if there is a start value first.

If this does not answer the question, please provide a minimal reproducer.

/Peter

[SudeepGhoshIN]

  Not able to get value for this 2 
    <ScalarVariable name="Constant4.Constant4" valueReference="50">
      <Integer start="3"/>
    </ScalarVariable>
        <ScalarVariable name="Out1" valueReference="28" causality="output">
      <Real start="1.0"/>
    </ScalarVariable>
    
    able to get value for 
        <ScalarVariable name="Parameters.FixPtConstant_Value_i" valueReference="16" causality="parameter" variability="tunable">
      <Real start="1.0"/>
    </ScalarVariable>

[PeterMeisrimelModelon]

Can you provide the corresponding C code for retrieving the start values?

/Peter

[SudeepGhoshIN]

fmi2_import_variable_t* var = fmi2_import_get_variable(varList, i);
baseType = fmi2_import_get_variable_base_type(var);
VariableType = fmi2_base_type_to_string(baseType);
if (VariableType == "Real")
{
fmi2_import_real_variable_t* rv = fmi2_import_get_variable_as_real(var);                    
fmi2_real_t StartValue = fmi2_import_get_real_variable_start(rv);  
}

[PeterMeisrimelModelon]

First off, there are couple of issues in your modelDescription.xml:

1. The first scalar variable does not specify a variability and thus fmi-library defaults to continuous. This conflicts with the variable being an Integer. Are you missing a variability="constant" here?
2. The second scalar variable does not specify variability or initial. Again, variability defaults to continuous and we take the default initial calculated (based on the variability + causality combination, see specification). initial="calculated" does not allow start values. There are multiple possible choices for initial here, but fmi-library does not perform checks to determine if any legal ones come without errors, it simply takes the default. You might want to specify a variability and possibly initial="exact" here?

As for the code, you'll want to obtain the type via fmi2_base_type_enu_t base_type = fmi2_import_get_variable_base_type(var); and use the enum for type checks and then pick the correct get_variable_as_* and get_*_variable_start functions based on the type.

/Peter