Hi
Thank you,
Makis
July 31, 2024, 2:55pm
2
I assume that this is the Cantera you mean:
and I assume that you want to get new properties in every step of the time loop.
Is this information based on a mesh, or are they uniform properties for the complete domain? While with preCICE you could of course provide a dummy, single-point mesh to just exchange such uniform properties, we are currently working on a feature to exchange quantities not associated with a mesh:
opened 09:19AM - 22 Nov 18 UTC
enhancement
For several applications users asked about sending global data, meaning data tha… t is not associated to a mesh. Examples:
* Angles between coordinate systems (CAMRAD-CFD)
* Global background pressure (fluid-acoustic coupling)
* Others that I forgot
Note: We have previously referred to this kind of data as meta data. In the end, I am not too happy with this expression as it let to confusion (exchanging strings, integers etc.). What I had in mind are physical values, thus floating point values only.
# User perspective
## Configuration
```xml
<solver-interface dimensions="2">
<data:scalar name="ClassicalMeshData"/>
<global-data:scalar name="GlobalData1"/>
<global-data:vector name="GlobalData2"/>
<mesh name="MeshName">
<use-data name="ClassicalMeshData"/>
</mesh>
<participant name="SolverName">
<use-mesh name="MeshName" provide="yes"/>
<write-data name="ClassicalMeshData" mesh="MeshName"/>
<write-data name="GlobalData1"/>
<read-data name="GlobalData2"/>
</participant>
<coupling-scheme:parallel-implicit>
<participants first="SolverName" second="..."/>
...
<exchange data="ClassicalMeshData" mesh="MeshName" from="SolverName" to="..."/>
<exchange data="GlobalData1" from="SolverName" to="..."/>
<exchange data="GlobalData2" from="..." to="SolverName"/>
...
<post-processing:IQN-ILS>
<data name="ClassicalMeshData" mesh="MeshName"/>
<data name="GlobalData1"/>
...
</post-processing:IQN-ILS>
</coupling-scheme:parallel-implicit>
```
## API
```c++
int getDataID ( const std::string& dataName ); // use same function name if possible
void setGlobalDataSize (
int dataID,
int size,
int* globalDataIDs );
// similar functions for reading and for scalar data
void writeGlobalVectorData (
int dataID,
int size,
int* globalDataIDs,
double* values );
```
I am not sure if we can avoid having sth like the above `setGlobalDataSize`. If we make this data structure completely dynamic, undefined behavior can appear. For instance, what happens if within one subcycled timestep two different sizes are given? Which one will be used? I currently also don't see a use-case where a completely dynamic size would be necessary (which does not mean that there isn't).
## Communication behavior
* Writing should be allowed on any rank. If data is written on multiple ranks, preCICE checks for consistency.
* On every reading rank, the same data is available
# Developer perspective
## Communication
* Gather on all writing ranks to master and check for consistency. This cannot be a debug-only feature, since we need to figure out either way on which rank data was written
* Send from master to master and broadcast
## WIP: Data structures and random thoughts
* New class `GlobalData` (in which package?? `mesh` would obviously lead to misunderstandings, probably a new package is needed)
* Do we need a `GlobalDataContext`? Maybe not
* Participant gets `_writeGlobalDataContexts` and `_readGlobalDataContexts` (or directly `_readGlobalDatas` or similar)
* How do we treat global data in `CouplingData`? New similar data structure? This has consequences in `_sendData` in `BaseCouplingScheme`
* How do we distinguish between the two send operations, normal m2n send and global data send in `M2N`, compare how sending the timestep size is currently handled
If this is information based on a mesh, you can extend the OpenFOAM adapter to read it as you wish: