DeterminismHash.hpp File Reference

Deterministic state-hash for CI golden testing. More...

#include "ecs/registry/Registry.hpp"
#include <cstdint>

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Namespaces
namespace	physics
	Pure physics math — no ECS types, no registry.
namespace	physics::diag

Functions
uint64_t	physics::diag::hashPhysicsState (const Registry &registry) noexcept
	Compute a deterministic hash of physics-relevant ECS state.

Detailed Description

Deterministic state-hash for CI golden testing.

Walks every replicated physics component on every entity in a stable (entity-id-sorted) order and folds their bits into a 64-bit FNV-1a hash. Two runs producing the same hash → bit-equal physics state.

Intended use:

1. CI runs a fixed-input scenario for N ticks twice; hashes must match.
2. Client + server hash the same tick's state; they must match (otherwise prediction is diverging).

Cost. O(entity count) per call, ~50 ns per entity on a typical CPU. Cheap enough to run every frame in dev / debug builds.