What is the meaning of Evaluate=true in a type definition?

[modelica-trac-importer]

Reported by pharman on 28 Sep 2012 11:25 UTC
In the MSL a number of enumeration type definitions have the annotation Evaluate=true. What is the intention of this?

Affected classes are:
Modelica.Blocks.Types.Init
Modelica.Blocks.Types.InitPID
Modelica.Blocks.Types.SimpleController
Modelica.Blocks.Types.AnalogFilter
Modelica.Blocks.Types.FilterType
Modelica.Mechanics.MultiBody.Types.Axis
Modelica.Mechanics.MultiBody.Types.RotationSequence
Modelica.Mechanics.MultiBody.Types.RotationTypes
Modelica.Media.Interfaces.Choices.Init
Modelica.Media.Interfaces.Choices.ReferenceEnthalpy
Modelica.Media.Interfaces.Choices.ReferenceEntropy
Modelica.Media.Interfaces.Choices.pd
Modelica.Media.Interfaces.Choices.Th

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Migrated-From: https://trac.modelica.org/Modelica/ticket/842

[modelica-trac-importer]

Comment by pharman on 9 Dec 2012 16:25 UTC
Since the specification states Has only an effect for a declaration with the prefix parameter. these have no effect.

Fixed by removing them in 66e1666

[modelica-trac-importer]

Comment by otter on 9 Dec 2012 22:06 UTC
Please, undo this change, since it will give at minimum disastrous results for MultiBody systems.

The types above with the Evaluate = true annotation are designed to be used in parameter definitions. In order to not repeat this definition at every parameter declaration, the annotation is defined at a type.

For MultiBody systems, the symbolic processing depends heavily on evaluating some key parameters, such as the axis of rotation of a revolute joint. If Evaluate = false is used for such a parameter, the number of operations in the generated code will be a factor of 2-3 larger (so the model evaluation will be about 2-3 times less efficient).

Other cases for Evaluate = true in the types are used since it shall be guaranteed that an if-clause is evaluated at translation time (and the parameter is used as condition in an if-clause).

[modelica-trac-importer]

Comment by pharman on 10 Dec 2012 09:50 UTC
Reverted changes in 787adf9.

Created new ticket #925 to add unspecified functionality to specification.