Incorrect context matching in configuration checks

[fsimonis]

Describe your setup

preCICE Version: 6552ffa (develop)

Describe the problem

In the configuration step, the local participant has an additional context including the local rank and the total amount of parallel ranks, analogous to MPI comm rank and size.

This size only makes sense to check, when the currently configured participant actually matches the local participant.

We use incomplete checks in:

1. precice/src/m2n/config/M2NConfiguration.cpp

   Lines 145 to 147 in 6552ffa

   	if (context.size == 1 && useTwoLevelInit) {
   	throw std::runtime_error{"To use two-level initialization, both participants need to run in parallel. If you want to run in serial please switch two-level initialization off."};
   	}

   
   Introduced in bacb133

2. precice/src/mapping/config/MappingConfiguration.cpp

   Lines 396 to 402 in 6552ffa

   	if (type == TYPE_AXIAL_GEOMETRIC_MULTISCALE && context.size > 1) {
   	throw std::runtime_error{"Axial geometric multiscale mapping is not available for parallel participants."};
   	}
   	if (type == TYPE_RADIAL_GEOMETRIC_MULTISCALE && context.size > 1) {
   	throw std::runtime_error{"Radial geometric multiscale mapping is not available for parallel participants."};
   	}

   
   Introduced in 9245132
3. ParticipantConfiguration: Meaningful mapping type disallowed #1965

Expected behaviour

Correctly check these conditions.

[uekerman]

1. is not very wrong, but we could add the participant name. Only makes a difference if there are multiple m2ns.
2. is indeed a bug.

[fsimonis]

Looks like 2 needs to be checked somewhere else altogether. MappingConfiguration has no idea which Participant it is attached to.

[MakisH]

Where would you suggest checking this?

This size only makes sense to check, when the currently configured participant actually matches the local participant.

I am not sure I understand: In which situation the currently configured would be different than the local?

[fsimonis]

In which situation the currently configured would be different than the local?

• A coupled to B, B coupled to C.
• A runs in parallel, B and C run in serial.
• C uses a geometric multiscale mapping
• Then participant A triggers this error.

I think this needs to be checked in the constructor of these Mappings for now. PRECICE_CHECK(!utils::IntraComm::isParallel(), "Not supported");