Question regarding ReserveTagPhysIDs

[saisandeepdammati]

Howdy!

I have a question regarding tags that being reserved for physics id based on enabled physics.

I see that if only HYDRO is enabled along with (NSCALARS > 0) in 2D, four physics ids (namely 1, 2, 3, 4) get reserved for hydro, and four physics ids (namely 5, 6, 7, 8) are reserved for NSCALARS. However, currently only cc_phys_id_ is set to value '1', cc_flx_phys_id_ is set to value '2' in HYDRO cell centered bvals followed by cc_phys_id_ = 5 and cc_flx_phys_id_ = 6 in NSCALARS cell centered bvals.

I am not sure where physics ids = 3, 4, 7, 8 are currently being used in the code? Are they currently left unused? Also, can we limit the max physics ids reserved for each of HYDRO, MAGNETIC_FIELDS, SELF_GRAVITY and NSCALARS by setting

static constexpr int max_phys_id in bvals_cc.hpp and bvals_fc.hpp to lower values say 2?

Thank you very much.

[felker]

athena/src/mesh/meshblock.cpp

Lines 141 to 167 in e34cd25

	// if (FLUID_ENABLED) {
	// if (this->hydro_block)
	phydro = new Hydro(this, pin);
	// } else
	// }
	// Regardless, advance MeshBlock's local counter (initialized to bvars_next_phys_id=1)
	// Greedy reservation of phys IDs (only 1 of 2 needed for Hydro if multilevel==false)
	pbval->AdvanceCounterPhysID(HydroBoundaryVariable::max_phys_id);
	// }
	if (MAGNETIC_FIELDS_ENABLED) {
	// if (this->field_block)
	pfield = new Field(this, pin);
	pbval->AdvanceCounterPhysID(FaceCenteredBoundaryVariable::max_phys_id);
	}
	if (SELF_GRAVITY_ENABLED) {
	// if (this->grav_block)
	pgrav = new Gravity(this, pin);
	pbval->AdvanceCounterPhysID(CellCenteredBoundaryVariable::max_phys_id);
	if (SELF_GRAVITY_ENABLED == 2)
	pmg = new MGGravity(pmy_mesh->pmgrd, this);
	}
	if (NSCALARS > 0) {
	// if (this->scalars_block)
	pscalars = new PassiveScalars(this, pin);
	pbval->AdvanceCounterPhysID(CellCenteredBoundaryVariable::max_phys_id);
	}
	// KGF: suboptimal solution, since developer must copy/paste BoundaryVariable derived

As the comment points out, we greedily reserve 4x IDs for hydro. All 4x of them are used for SMR/AMR calculations.

Why do you want to lower the reserved IDs?