# Practical Project#

The course requires to develop a hybrid software system of C++11 (modern C++) and Python for a numerical, scientific, or engineering problem. Everyone needs to write a proposal, develop the code, and present the project to the class at the end of the course.

The software needs to be open-source and hosted on github.com. It should be executable through command line. Building the software should use a single command.

A proposal needs to be written before developing the project. It serves as a plan for the code development. Please follow Proposal Template and make it work like a specification, which is used to discuss what you want to do and how you will do it. You may also reference a sample project proposal: (A Sample Project Proposal) SimpleArray for Multi-Dimensional Field.

With your proposal, I can help you manage the development through discussions (at which you should be pro-active). A plan will not be 100% accurate and you should modify it as you go. Use pull requests to keep the proposal up-to-date.

You should write prototype code for your project with the proposal. The initial work will help you understand more about what to do. It is difficult to write a proposal without prototyping.

## Assessment#

The project will be assessed based on the following guidelines: good engineering infrastructure, correct implementation and solution to the problem, adequate architecture, and clear presentation.

### Software Engineering#

### Correctness#

Existence of golden

Quality of golden

Sequence of development [adv]

### Software Architecture#

### Presentation#

Technical fluency

Slide clarity

Time control

Appearance

## Sample Topics#

Some possible topics are listed in what follows. They are of real use cases for the teaching code modmesh. You may use a topic derived from them, but also encouraged to come up with an original one.

### Contiguous Array#

Multi-dimensional arrays of fundamental types and struct are a building block for numerical code. It may be as simple as a pointer to a contiguous memory buffer, or well-designed meta-data with the memory buffer. While a mere pointer works well with one-dimensional arrays, calculating the pointer offset for multi-dimensional arrays makes the code for numerical calculation cryptic and hard to maintain. It is very helpful to wrap the multi-dimensional index calculation in a library.

A handy multi-dimensional array library should provide the following features:

No more runtime overhead than the calculation of the pointer offset.

Allow safe sharing of the memory buffer to other library and language in the same process. This feature is the so-called zero-copy. Sharing the buffer with other process using OS-provided shared memory should not be forbidden.

Support both fundamental types as well as composite types (struct).

### Columnar Array#

There are generally two ways to implement arrays of composite types. One is to pack the composite data and use an array for them, i.e., the so-called array of struct (AoS):

```
struct Data
{
int m_field1;
double m_field2;
};
SimpleArray<Data> data_array;
```

The other is to organize arrays of fundamental types, i.e., the so-called struct of arrays (SoA) or the columnar arrays:

```
struct StructOfArray
{
SimpleArray<int32_t> m_field1;
SimpleArray<double> m_field2;
};
```

In the columnar array, if the fields are considered as the “rows” in a two-dimensional array, the data organization is like the “column-major” format. This is why we use the term “columnar” to describe this kinds of data structure. The columnar array (SoA) may provide better cache locality than AoS, especially when there are many fields. For example, if there are 8 fields of double-precision floating point, each “row” will totally occupy a cache line of 64 bytes.

Note

The columnar array is usually two-dimensional and works like a table.

The requirements of the columnar array library:

A single class template can create the columnar array.

Automatic generate a row-accessor. The row-accessor works as a handle (or cursor) over all rows in the array.

References

### Graph Partitioning#

Numerical solution of partial differential equations (PDEs) depends on discretization of space. The entities describing the discretized space are called grid or mesh. The mesh can be broadly categorized into structured and unstructured mesh. The latter is more flexible than the former.

The unstructured mesh allows free connectivity, which enables flexible distribution of data for parallel computing. The connectivity between mesh elements can be represented as a graph, and the graph is used for partitioning. The graph-partitioning problem is useful to minimizing the communication between sub-mesh.

The graph partitioning code should support:

Extract a graph from a two- or three-dimensional unstructured mesh of mixed elements.

Find the sub-graphs whose edges across each other are minimized.

Use the sub-graphs to decompose the original mesh into inter-connected sub meshes.

### R-Tree Search Engine#

R-tree is an index to speed up searches in space. It is usually referred to as a spatial index or just a tree. In one-dimensional space, a common search tree may be used because it may use a single key for search. In multiple-dimensional space, there are intrinsically multiple keys, so the search tree needs to accommodate the dimensionality. Data structures of the similar purpose include k-d tree, quad-tree, etc.

The requirements of an implementation of the R-Tree search engine are:

It works in two- or three-dimensional space and may index point, line, surface, or volume.

Allow dynamic update of elements.

Allow access elements using a serial (integer) identifier.

Support ranged search of the geometrical entities.

References

### Voronoi Diagram#

The Voronoi diagram is a decomposition of a region that any point in a sub-region is closest to the site of the sub-region. A classical example is to determine the service areas of each branch of a reseller chain. Our interest of this problem is to discretize space for mesh generation. It can be used to create triangular mesh in the Delaunay triangulation.

The requirements of the Voronoi diagram code are:

Given geometrical entities in two- or three-dimensional space, find the Voronoi diagram.

The data structure allows accessing the geometrical entities and the Voronoi diagram using a serial (integer) number. The index access implies the entities and the Voronoi diagram are associated with each other.

Fast searching for nearby entities is supported with a spatial index.

### Mesh Data Conversion#

Numerical solution of partial differential equations (PDEs) depends on discretization of space. The entities describing the discretized space are called grid or mesh. To successful carry out the numerical analysis, there are 3 types of codes: (i) a mesh generator creates the mesh, (ii) a solver computes the solution, and (iii) a visualizer provides the analysis. The mesh data play a central role among the codes.

Different codes take different formats for the mesh data. There needs to be another code to convert the mesh and solution data for the corresponding codes. The converting code should work as a standalone executable. It will be good if the code also works as a library to be plugged in other associated codes for easier automation.

Examples of the numerical analytical codes:

### Parametric Description of Curved Geometry#

To describe the smooth geometry of an object in space, Bezier curves are usually used. The spatial discretization may be applied on the objects for numerical calculation.

The requirements of the Bezier code:

Computation mesh can be generated against the curved objects in two- or three-dimensional space.

The mesh can be associated with the curved geometry, preferably with serial (integer) identifiers.

### Boolean Operations on Polygons#

In Euclidean space we are interested in finding the Boolean, i.e., AND, OR, NOT, XOR, of polygons. The polygonal Boolean operations are useful when we want to extract geometrical properties of the graphics. In two-dimensional space we deal with polygons. In three-dimensional space it is polyhedra.

References