This repo contains a personal game project of mine that turned into research on in-memory database techniques for Entity Component Systems (ECSs). The interesting bits you'll find in this repo are:

• An MB+ tree implementation. This is a variant of B+ trees that always contains three levels and uses a sorted contiguous array at the root, which exploits the fact that the workload of a B+ tree closer to the root is read-heavy.
• A columnar representation that provides nice syntax for manipulation of database rows via C++ templates. Boost MPL is used for template metaprogramming.
• A set of operations for building queries over MB+ tree indices (see the various files in Game/Database). For example, MergeJoin.h provides a join for indices on the same key, while FindJoin.h works for any indices. The query operators are all implemented as C++ templates, which enables AoT code generation game simulations where all required queries are typically known ahead-of-time.
• A work-stealing task system implemented on top of User-Mode Scheduling. UMS threads strike a balance between system threads (each UMS thread has its own stack) and fibers (UMS threads are scheduled in user-mode). While this was a fun technology to learn about, UMS was already being deprecated when I built this and no longer exists in Windows 11, so this part is unlikely to be useful today.
• A game loop implementation that uses filtered moving averages to predict both simulation and rendering times, and uses those predictions to achieve smooth frame pacing.