Important types

Table of Contents

• SEM foundation types
• Basic math routines
• Governing equation solvers and related types
• Singletons
• Linear algebra

This section is meant to help new developers get a quick introduction to some of the most important types in Neko, to get an idea of where to look for what. In this spirit, the descriptions here are not meant to be exhaustive. In many cases, we will just point to top type in a hierarchy, and leave the reader to explore the descendants.

SEM foundation types

• mesh_t: The computational mesh.
• space_t: The function space in which the solution is sought. Contains things related to the polynomial basis within each element.
• dofmap_t: Map of degrees of freedom. Most importantly, it holds all the GLL nodes locations.
• coef_t: Stores coefficients for transformation to and from the reference element, along with some other auxillary data.
• gs_t: Gather-scatter kernels used to make the solution continuous, i.e. perform direct stiffness summation.
• field_t: The main type for storing the unknowns, and essentially everything else that lives on the mesh.

Basic math routines

Here, we also list file names rather than types, since the basic math is implemented as subroutines.

• math.f90: Basic math operations on raw arrays.
• device_math.F90: Basic math operations on device arrays.
• field_math.f90: Basic math operations on field_t.
• operators.f90: Various explicit operators, including derivatives, etc.
• vector_t and matrix_t: 1D and 2D arrays with support for computation on accelerators.

Governing equation solvers and related types

• case_t: An abstraction for the simulation case. Stores the fluid and scalar solver as components, handles IO via sampler_t.
• fluid_scheme_t: Navier-Stokes solvers.
• scalar_scheme_t: Scalar advection-diffusion-reaction solvers.
• bc_t: Boundary conditions.
• time_scheme_t: Time integration schemes.
• source_term_t: Source terms.

Singletons

Singleton types are meant to only have a single object of their kind to be created. These objects are declared in the same module where the type resides, and all have their name starting with neko_.

• field_registry_t: A registry of field_t, retrievable by name or index. This is the main object used to access the fields of unknowns for any place in the code.
• scratch_registry_t: Provides a mechanism to get a temporary field_t for doing some work. Use this instead of creating temporary fields inside a subroutine.
• simcomp_executor_t: Driver for simulation components. The object is called neko_simcomps.
• log_t: Used to write to the simulation log.

Linear algebra

• ksp_t: Krylov solvers.
• pc_t: Preconditioners.