== Instrument the Code
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!VisIt provides numerous examples how to make use of its in-situ library libsim.
 * [http://visit.ilight.com/svn/visit/branches/2.10RC/src/tools/DataManualExamples/Simulations/ example codes]
 * [wiki:VisIt/libsim libsim functions]

In the following our own Fortran90 implementation is discussed.

[[Image(VisIt-libsim-loop.png, align=right, margin=10, height=300)]]
   * Fortran90 example (from [http://www.fz-juelich.de/ias/jsc/EN/Expertise/High-Q-Club/psOpen/_node.htm psOpen]): [attachment:psopen_visit.F90 psOpen_visit.F90]


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=== Instruction-Paths in Flow-Diagram for different Modes
|| Mode               || Diagram ||
||run + never update \\ * simulation is running in max. speed \\ * plots are NOT updated \\ * ONLY check for new commands  ||[[Image(VisIt-libsim-loop_run-noupdate.png,  align=right, margin=10, height=150)]]
||run + always update \\ * simulation is interrupted EVERY iteration \\ * plots are ALWAYS updated \\ * ALWAYS check for new commands ||[[Image(VisIt-libsim-loop_run.png,   align=right, margin=10, height=150)]]
||pause             ||[[Image(VisIt-libsim-loop_pause.png, align=right, margin=10, height=150)]]
||step              ||[[Image(VisIt-libsim-loop_step.png,  align=right, margin=10, height=150)]]
||run-update-now    ||[[Image(VisIt-libsim-loop.png, align=right, margin=10, height=150)]]
||run-update-never  ||[[Image(VisIt-libsim-loop.png, align=right, margin=10, height=150)]]
||run-update-always ||[[Image(VisIt-libsim-loop.png, align=right, margin=10, height=150)]]




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any feedback welcomed - [mailto:h.zilken@fz.juelich.de], [mailto:j.goebbert@fz-juelich.de]