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===== Advanced GroIMP arguments =====

GroIMP can be started with additional arguments for both Java, and GroIMP itself.

A typical command to start GroIMP is :

> java -Xverify:none -jar core.jar --project-tree

The command above can be split in two:
  - the java command and arguments
  - the GroIMP arguments

=== The java arguments ===

In the given example, the java command is ''java -Xverify:none -jar core.jar''.

There are two java arguments: 
  - ''-Xverify:none'', this argument is required in versions of GroIMP > 1.6, but not for Java >=17.
  - ''-jar core.jar'', this argument points at the jar file that contains the Main GroIMP classes. Note that depending on how GroIMP is packaged, the name of the .jar file can change. This argument is **always** the last java argument of the command line.

Java arguments MUST be given before the argument `-jar core.jar`. All arguments given after are pushed to GroIMP and not to the JVM.

A non exhaustive list of common Java arguments used with GroIMP:
  - ''-Xverify:none'' required for java >1.6 & <17.
  - ''-Xmx3000m'' sets the maximum heap size the JVM have access (here to 3GB). If your projects fail at runtime due to memory issues, you probably want to increase this value.
  - ''-Xss1m'' set threads stack size limit. Some GroIMP models may require a lot of memory for compilation (when you save or open a model). If your project fails at compilation due to memory issues, you probably need to increase this value. Be careful, however, the memory allocated due to this argument is pushed to **all** threads created by GroIMP. Thus, it can lead to huge memory consumption.

**Note: if you run GroIMP from Eclipse, the java arguments can be set in the Run Configuration...>x() = Arguments>JVM arguments**

=== The GroIMP arguments ===

In the given example, the GroIMP argument is ''--project-tree''.

All arguments given after the ''-jar core.jar'' are GroIMP arguments. 

A non exhaustive list of common Java arguments used with GroIMP:
  - ''--project-tree'' this argument is used when GroIMP is run in Eclipse, it tells GroIMP to load classes under the local /PLUGIN/target/classes/ repositories where PLUGIN is the name of each directory at the root of GroIMP. This path is different when GroIMP is run after packaging. By default GroIMP loads classes in ./plugins/PLUGIN/PLUGIN.jar where PLUGIN is the name of each plugin.
  - ''--headless'' this argument starts GroIMP headless, i.e. without a graphical interface. Usually, you also define the project to open as an argument (see 4.).
  - ''-a api'' this argument defines which application will be started (currently available applications: ''imp'', ''cli'', ''api''). By default GroIMP starts with ''imp''.
  - ''-p /path/to/a/directory/'' links a directory to the list of loaded plugins. 
  - ''path/to/a/model.gsz'' this argument **requires** to be used last. It gives a model to be opened after start.


See more:
  * [[:user-guide:command-line-arguments|All command line arguments]]

== Additional model specific parameters ==

It is possible to forward parameters from the command line to the GroIMP simulation using additional parameters beginning with an capital X.
For example, for a variable called number with the value 5 the additional parameter would be ''-Xnumber=5''. This value can then in the simulation be recalled by ''Main.getProperty("number")'' 

A tutorial for this can be found [[:Tutorials:xparametric-model|here]]

**Note: if you run GroIMP from Eclipse, the GroIMP arguments can be set in the Run Configuration...>x() = Arguments>Program arguments**