The purpose of src/data provide open run time extensible structured data. More...

#include "fe/data.h"
#include <math.h>

Include dependency graph for xDataPrimer.cc:

Macros
#define	DT 1.0e-4

#define	ST 0.1

Functions
void	print_group (sp< RecordGroup > spRecordGroup)

sp< RecordGroup >	hello_world (sp< Master > spMaster)

void	using_accessors (sp< Scope > spScope)

void	add_heterogenous_dataset (sp< RecordGroup > spRecordGroup)

void	using_accessorsets (sp< RecordGroup > spRecordGroup)

void	gravity (Real &force_A, const Real &location_A, const Real &mass_A, Real &force_B, const Real &location_B, const Real &mass_B)

void	viscosity (Real &force_A, const Real &velocity_A)

void	integrate (Real &location, Real &velocity, const Real &force, const Real &mass, const Real &dt)

void	access_pattern_basic (sp< RecordGroup > spRecordGroup)

void	access_pattern_recordarray (sp< RecordGroup > spRecordGroup)

void	access_pattern_layout (sp< Scope > spScope)

void	access_pattern_compile (sp< RecordGroup > spRecordGroup)

void	schema_example (void)

void	write_files (sp< RecordGroup > spRecordGroup)

void	read_files (sp< Scope > spScope, sp< RecordGroup > &spRGFromAscii, sp< RecordGroup > &spRGFromBinary)

String	colorize_src_data (const std::string &ascii_text)

int	main (void)

Variables
const char *	schema_rg

const char *	body_rg

Detailed Description

The purpose of src/data provide open run time extensible structured data.

Precedents range from Houdini and Maya data systems to game ECS systems.

Please see Data System Primer for a full discussion.

What

Overview

Runtime Aggregate Typed Data System – An aggregation of attributes defines this notion of "type". This manifests as both a form of implicit typing (akin to python "duck" typing, where a thing is a thing because it has the attributes of that thing), and an explicit form (where a thing is constructed as a thing with a strict set of attributes).

This leads directly to analogy with other cases, such as Maya, Houdini, USD, etc. However, one of the closest patterns to compare is the Entity Component System (ECS) pattern.

Distilled from https://en.wikipedia.org/wiki/Entity_component_system:

Entity: The entity is a general purpose object. Usually, it only consists of a unique id.
Component: The raw data for one aspect of the object, and how it interacts with the world.
System: Each System runs continuouslyand performs global actions on every Entity that possesses a Component of the same aspect as that System.

src/data overlaps with the above definition. src/data does not directly facilitate the "System" part, but rather defers the functionality aspect to src/plugin. However, src/data extends the concept of Entity to a Typed Entity, which improves on the ECS pattern's power and can be used for more optimized implementation without losing usability. Therefore, the src/data pattern could be termed: Typed Entity Components for Systems (TEC-S)

A good reason to relate src/data to ECS is that ECS has a lot of stuff written about it which applies to src/data, including the value of the run time part of it, and the tradeoffs in such.

Specifically

The Basic Summary (non circular)

Scopes are namespaces, and everything else is within a Scope
Attributes are named types. Attribute instances are data.
Layouts define a set of attributes, so they are "aggregate types"
Records contain instances of attributes according to a Layout
RecordGroups contain Records

The terms used in traditional ECS map roughly to these src/data terms.

Entity Type: Layout
Entity: Record
Component: Attribute
System: src/plugin

Deep

The way data is actually stored in src/data has some compile time options. The original src/data implementation stored data in what were called State Blocks (SB), which is an Array of Structures (AoS) approach.

In order to improve performance, a Structure of Arrays (SoA) approach was added using what were called Attribute Vectors (AV).

Finally, to improve performance even more, for intense inner loop system cases, more direct access to the Attribute Vectors in a heterogenously usable way was added. Here we call that AV'.

SB: AoS (FE_DATA_STORE==FE_SB) – 20200601: possibly deprecated
AV: SoA (FE_DATA_STORE==FE_AV)
AV': SoA with more direct access enabled (FE_AV_FASTITER_ENABLE)

How

error checking kept to a minimum for clarity of this guide
good practice would be to check sp's for validity, etc
Master
Hello World
- Types
- Scope
- Attribute
- Layout
- Record
- Accessors
- RecordGroup
Using Accessors
Adding Data
Using AccessorSets
Data Access Methods
- Access Pattern: Basic
- Access Pattern: RecordArray
- Access Pattern: Layout
- Access Pattern: Compile
Schemas
- Writing Files
- Reading Files

Variable Documentation

◆ body_rg

const char* body_rg

Initial value:

= "                 \
RECORD 0 particle                       \
    location 0.1                        \
RECORD 1 particle                       \
    location 0.3                        \
"

◆ schema_rg

const char* schema_rg