With a watch point, you can track the coupling data values at a certain position over time. This is very handy for applications such as the Turek and Hron FSI3 benchmark where you want to analyze the movement of the tip of a flexible plate. 
<participant name="MySolver1">
    <provide-mesh name="MyMesh1"/>
    ...
    <watch-point mesh="MyMesh1" name="MyWatchPoint" coordinate="0.6; 0.2"/>
    ...
</participant>

This will create a logging file precice-MySolver1-watchpoint-MyWatchPoint.log with one row per time step.

  • Only a participant that provides the respective mesh can set a watchpoint on that mesh.
  • You can freely choose the name MyWatchPoint.
  • Please note the format of coordinate. Here, values at (x,y)=(0.6,0.2) are tracked. The dimensions need to match the overall preCICE dimensions in the mesh tag of your preCICE configuration.
  • If (0.6, 0.2) is not explicitly a vertex of MyMesh1, the nearest neighbor is chosen (resp. nearest projection if mesh connectivity is defined, cf. the mapping configuration).
  • The dimensions of the watchpoint need to match the dimensions of the interface (2D vs. 3D).

You can plot watchpoints using gnuplot. See an example from our tutorials.