A slot: the current column position of a row. i is the slot under discussion, j a second one. A slot is not stable - sort and swap_remove move rows between slots (§9, §21).
t or tick
Tick number - the simulator’s step counter.
id
A stable entity identifier that travels with a row across reorders, unlike its slot (§10). A small unsigned integer, usually np.uint32.
gen
Generation counter, paired with a slot index to detect stale references (§10).
pos_x, pos_y
Position columns of a creature (np.float32).
vel_x, vel_y
Velocity columns of a creature (np.float32).
to_remove, to_insert
Buffers of pending mutations applied at end-of-tick (§22).
n_active
Length of the live prefix of a fixed-capacity column (§21, §24).
Structure of Arrays - each field is its own column.
AoS
Array of Structures - each row is its own object (tuple, dataclass, or class instance).
DAG
Directed Acyclic Graph
RSS
Resident Set Size - the physical memory a process holds, as the OS reports it
IOPS
I/O Operations Per Second
TDD
Test-Driven Development
LRU
Least Recently Used (cache eviction policy)
OOM
Out Of Memory (the allocator fails, or the OS OOM-killer steps in)
IPC
Inter-Process Communication
SMT
Simultaneous Multi-Threading (two hardware threads sharing one core)
ISA
Instruction Set Architecture
ORM
Object-Relational Mapper (the row-per-object database layer §36 critiques)
EBP is this book’s shorthand. The spelled-out term - existence-based processing - is Richard Fabian’s, from Data-Oriented Design; §17 introduces it from the simulator. An acronym index will not list “EBP” because the source literature spells the term out rather than abbreviating it.