ONELAB parameters can be created, accessed and modified using several commands in Gmsh (.geo) and GetDP (.pro) input files:

• n = DefineNumber[ 3.14, Name "a number", <attributes...>];

• s = DefineString["hello", Name "a string", <attributes...>];

• DefineConstant [ n = {3.14, Name "a number", <attributes...>} , s = {"hello", Name "a string", <attributes>} , ...] ;

• SetNumber[ "a number", 3.14 ]; n = GetNumber["a number"];

• SetString[ "a string", "hello" ]; s = GetString["a string"];

In addition, GetDP defines two functions to access ONELAB parameters at run-time, i.e. during pre-processing, processing or post-processing operations (in contrast to the commands above, which are executed when the .pro files are parsed):

• SetNumberRunTime[ 3.14 ]{"a number"}

• n = GetNumberRunTime[]{"a number"}

Finally, GetDP also defines a SendToServer option in its PostOperation object, to send post-processing results directly to the ONELAB database.

Commands

DefineNumber and DefineString

The purpose of these commands is to associate a local variable in the namespace of Gmsh or GetDP with a shared parameter in the ONELAB database whose value is accessible to all clients and can be set interactively by the user in the graphical user interface.

When an input .geo or .pro file is parsed, the command

n = DefineNumber[ 3.14, Name "a number", <attributes...>];

first checks if a ONELAB parameter with name "a number" exists in the ONELAB database.

• If it does not, the parameter "a number" is added to the ONELAB database with value 3.14, and the same value is also assigned to the local variable n in the namespace of Gmsh or GetDP.
• If it does, it is the value fetched from the ONELAB database that is assigned to the local variable n, and the value given in the argument of the command is ignored.

This means that 3.14 can be interpreted as a default value for the local variable n (and for the ONELAB parameter "a number"): the first time the statement n = DefineNumber[ 3.14, Name "a number"] is parsed, the local variable n is assigned the default value 3.14. All subsequent executions of a command like n = DefineNumber[ 2.718, Name "a number"] (either in the same file if it is parsed again or in another file) will ignore the argument value 2.718, and assign to the local variable n the value of "a number" obtained from the ONELAB database. That value could be the original default value, or a value set in the meantime by the user via the graphical user interface, or a value set by another ONELAB client.

Sometimes the opposite behavior is useful. This is done by giving the ONELAB parameter the attribute ReadOnly 1, e.g. by means of the command

n = DefineNumber[2.718, Name "a number", ReadOnly 1, <attributes...> ];

In this case, the parameter "a number" in the ONELAB database and the local variable n are both assigned the argument value, here 2.718. All subsequent n = DefineNumber[ xx , Name "a number"] statements will have the same behavior, as long as the attribute ReadOnly of the parameter "a number" is not reverted to 0. Logically, ReadOnly parameters are not editable in the graphical user interface.

A / character in a parameter name results in the creation of a sub-tree in the hierarchical parameter tree displayed in the graphical user interface. See also below for all the optional attributes that can be specified in addition to the Name of the parameter.

If no ONELAB server exists (e.g. if GetDP is run in stand-alone mode), the DefineNumber command simply assigns the default value 3.14 to the local variable n. An input file using DefineNumber to create an appealing graphical user interface using ONELAB can thus also be run as-is without ONELAB.

A similar syntax can be used to define string parameters:

s = DefineString["hello", Name "a string", <attributes...>];

See below for all the optional attributes that can be specified in addition to the Name of the parameter.

The behavior of DefineNumber and DefineString is similar to the behavior of the functions with the same names in Python clients.

Examples

x = DefineNumber[1, Name "My variable"];
x = DefineNumber[1, Name "My variable", Choices {0,1}];
x = DefineNumber[1, Name "My variable", Choices {0,3,5}];
x = DefineNumber[1, Name "My variable", Choices {0="Zero",3="Three", 5="Five"}];
x = DefineNumber[1, Name "My variable", Min 0, Max 50, Step 5}]
x = DefineNumber[1, Name "Variables/Input/My variable", Min 0, Max 50, Step 5];
y = DefineNumber[2. * x, Name "My read-only variable y = 2*x", ReadOnly 1];
s = DefineString["a", Name "My string variable"];
s = DefineString["a", Name "My string variable", Choices {"a", "b", "c"}];
s = DefineString["a", Name "My string variable", Kind "File"]
s = DefineString["a", Name "Variables/Input/My string variable"];

DefineConstant

DefineConstant builds on the functionality of DefineNumber and DefineString, and adds useful features for constructing generic parametric models.

When an input .geo or .pro file is parsed, the command

DefineConstant [ n = {3.14, Name "a number", <attributes...>} ];

first checks if the local variable n exists. If it does not exist, the command behaves as n = DefineNumber[3.14, Name "a number"]. If it does exist, the DefineConstant command is skipped and the ONELAB parameter is not created. DefineConstant[n = {3.14, Name "a number"}] is thus a shortcut for

If(!Exists(n))
  n = DefineNumber[3.14, Name "a number"];
EndIf

DefineConstant can also be used to define several constants at once, mixing numbers and strings:

DefineConstant [ 
  n = {3.14, Name "a number", <attributes...>}, 
  s = {"hello", Name "a string", <attributes...>}
];

As with DefineNumber and DefineString, if a ONELAB server does not exists the DefineConstant command simply assigns the default values to the local variables.

When creating generic parametric models, several input files are usually combined, using Include to merge generic definitions in more specific models. For example, let us assume that a generic model in the file generic_model.pro contains the following code:

DefineConstant[ flag = {1, Choices{1,2,3}, Name "a flag changing the behavior of the model"}];
// the model uses this flag to control the model behavior

Let us now consider a more specific model, that uses the generic model but only makes sense for a specific value of flag, say 2. Instead of modifying the generic model to suit the needs of the specific model, the specific model can simply be written as

flag = 2;
Include "generic_model.pro"

The user-visible ONELAB variable "a flag changing the behavior of the model" will never be defined, and for the user of the specific model, everything behaves as if flag is not a parameter.

Note that in addition to setting the values of the local variables in the input .geo and .pro files, both Gmsh and GetDP allow to pass local variable definitions on the command line, with the -setnumber name value and -setstring name value command line options.

Examples

DefineConstant[ x = {1, Name "My variable"} ];
DefineConstant[ x = {1, Name "My variable", Choices {0,3,5}} ,
                y = {2. * x, Name "My read-only variable y = 2*x", ReadOnly 1},
                s = {"a", Name "My string variable"} ];

SetNumber, SetString, GetNumber and GetString

SetNumber, SetString, GetNumber and GetString allow to perform direct basic queries in the ONELAB database:

SetNumber[ "a number", 1 ];
SetString[ "a string", "1" ];
a = GetNumber["a number"];
s = GetString["a string"];

Currently these basic functions do not allow setting optional ONELAB attributes.

SetNumberRunTime and GetNumberRunTime (GetDP only)

All the above commands (DefineNumber, DefineString, DefineConstant, SetNumber, SetString, GetNumber and GetString) are executed when the input data files for GetDP and Gmsh are parsed. For GetDP, this means that the queries in the database using these commands are done once, when the .pro file is analyzed.

However, in some situations, one might want to exchange information with the ONELAB database while the computation is running, i.e. at ''run-time''. GetDP defines two built-in functions (at the same level as other GetDP functions like X[] or Vector[]) that allow to exchange numbers at run-time, while evaluating expressions:

SetNumberRunTime[ 3.14 ]{"a number"}
GetNumberRunTime[]{"a number"}

These functions can be used in all the same places that other GetDP expressions can be used, e.g. in Function definitions, Formulation terms, inside the Evaluate operation in a Resolution, etc.

SendToServer (GetDP only)

See the GetDP documentation for more information.

Optional parameter attributes

Common attributes

Here's the list of attributes available for all ONELAB parameters:

• Name "string": The name of the parameter in the ONELAB database, in the form of a /-separated path. The Name attribute is mandatory to exchange the variable with the ONELAB server. If no name (and no other attribute) is given, the DefineConstant construct can be used to assign default values to local variables (which will not be sent to the ONELAB server).

• ReadOnly 0|1: If ReadOnly is set, the value cannot be changed server-side (e.g. interactively in the graphical user interface), and the value provided in DefineNumber, DefineConstant, etc., is always used.

• Highlight "string": Color used to draw the widget in the graphical interface.

• Visible 0|1: Should the parameter be visible in the interface?

• Closed 0|1: Should the subtree containing this variable be closed?

• Help "string": Help string for this parameter.

• AutoCheck 0|1: Allows to disable automatic "check" (rebuild of the interface) when the value is changed.

• GmshOption "string": Treats the parameter as the name of a Gmsh option (e.g. Mesh.Algorithm).

• ServerAction "string": Performs the ONELAB server action "string" when the parameter is changed. Currently supported actions are "Reset" (to force a full model reset), "ResetDatabase" (to force a full database reset) and "Reset name1, name2, ..." (to force a reset of the listed variables). The "Reset name1, name2, ..." form allows to create master/slave variables where the slave variables can still be edited server-side, contrary to ReadOnly variables. For example:

DefineConstant[
  a = {1, Name "var1", Label "Master variable", ServerAction "Reset var3"}
  b = {a*2, Name "var2", Label "Slave (x 2) variable", ReadOnly 1}
  c = {a*2, Name "var3", Label "Editable slave (x 2) variable"}
  d = {a*2, Name "var4", Label "Standard (x 2) variable"}
];

• Label "string": Alternative label used in the graphical user interface, replacing the part of Name located after the last /.

• Units "string": Appends the given string after the variable name between square brackets.

• ChangedValue number: The value that the changed flag will take when the parameter is updated. A zero value thus means that the parameter will appear as never having being changed. Gmsh treats changed flag values as follows: if changed=1, only the mesh is saved; if changed=2, the model is first remeshed, then the mesh is saved; if changed=3, the model is first reloaded, then remeshed and finally saved.

Number attributes

In addition, numbers can take the following specific attributes:

• Min number: Minimum value allowed when scrolling in the interface, and when looping on the parameter

• Max number: Maximum value allowed when scrolling in the interface, and when looping on the parameter

• Step number: Step value used when scrolling in the interface, and when looping on the parameter

• Range {min, max, step}: Alternate syntax for Min, Max and Step

• Choices {number, number, ...}: Possible choices for the parameter

• Choices {number="string", number="string", ...}: Possible choices for the parameter, with string labels for each choice

• ReadOnlyRange 0|1: Treat the range (or the choices, if they are provided) as read-only

• Loop "string": Loop over the parameter (the string indicates the loop imbrication level: currently "1", "2" or "3")

• Graph "string": Display the list of values stored in the choices attribute as a 2D graph. The string encodes for which coordinate (x or y) in the predefined graphs (top left, top right, ...) the values will be used. Each graph is encoded as 4 characters, corresponding to the use of the values as the x, y, x' and y' coordinates (x' and y' are used when two curves should be drawn on the same graph): possible character values are 0 (value not used), 1 (iso-values), 2 (continuous map), 3 (discrete map), 4 (numeric value). The first group of 4 characters controls the pre-defined top-left graph, the second group controls the top-right graph, etc. For example, the string "0200" will use the values for the y coordinates on the top-left graph, displaying the curve with the continuous style; the string "10000200" will use the data for the x coordinates on the top-left graph and also use them as the y coordinates on the top-right graph.

String attributes

String accepts the following specific attributes:

• Kind "string": Mutable kind of the string (currently: "file")

• Choices {"string", "string", ...}: Possible choices for the parameter

• MultipleSelection "string": Allow multiple selection in choices. The string indicates the initial selection pattern, e.g. "1001111".

• Macro "string": If "string" is "GmshMergeFile", the parameter is treated as a filename of a macro that will be merged when the parameter is clicked in the interface. If string is "GmshParseString", the parameter is directly treated as a Gmsh macro that will be parsed when the parameter is clicked in the interface.