djglaze
commented
7 months ago @psakievich This commit doesn't conflict with your commit #1236, so there isn't an order dependence for merging. This has the bug from last time fixed.
I agree with your comment in #1236, where it would make sense to change the SmartField retrieval template parameter to something like: fieldManager_.get_legacy_smart_field<double>("temperature") instead of the current fieldManager_.get_legacy_smart_field<sierra::nalu::ScalarFieldType>("temperature"). After this simple_fields change, the Field typedefs no longer convey any useful meaning beyond just the datatype. Using ScalarFieldType vs. VectorFieldType would yield identical results, which is a bit confusing.
psakievich
STK is migrating to a new strategy for registering and managing Fields, where sizing information is purely specified at run-time instead of the previous technique of specifying it in a confusing blend of both compile-time and run-time information. The compile-time specification was just a suggestion, as it could be overridden (possibly inconsistently) at run-time to support variable-length Fields. This made it unclear what the true size of a Field was and where it should be specified.
As an example, registering a vector field on the entire mesh previously looked like this:
using VectorField = stk::mesh::Field<double, stk::mesh::Cartesian3d>; VectorField & field = meta.declare_field(stk::topology::NODE_RANK, "velocity");
stk::mesh::put_field_on_mesh(field, meta.universal_part(), 3, nullptr);
and now, it looks like this:
using VectorField = stk::mesh::Field;
VectorField & field = meta.declare_field(stk::topology::NODE_RANK, "velocity");
stk::mesh::put_field_on_mesh(field, meta.universal_part(), 3, nullptr);
stk::io::set_field_output_type(field, stk::io::FieldOutputType::VECTOR_3D); // Optional
The only template parameter for a Field is now the datatype parameter. Sizing information now exclusively comes from put_field_on_mesh() calls. The optional set_field_output_type() function call registers with the IO sub-system how a multi-component Field should be subscripted in Exodus files. If this call is left off, you will get the default [_1, _2, _3] subscripting. With the above call, you will instead get [_x, _y, _z] subscripting.
The MetaData::use_simple_fields() flag is set everywhere possible in the code to prevent accidental regressions before the old behavior is formally deprecated and removed. This will yield a run-time error if the old-style extra template parameters are used anywhere. These calls to use_simple_fields() can be removed in the future once the STK Mesh back-end has removed support for the old behavior.
This wasn't a completely straightforward conversion due to nalu-wind making heavy use of various algorithm selections based on the templated Field type. The ScalarFieldType, VectorFieldType, TensorFieldType, and GenericFieldType types are now all identical, so different techniques had to be used to switch behaviors.