Memory model. Chaining allocates a node per inserted key, which means malloc (fragmentation, non-determinism, the allocation problems) or maintaining a node pool, plus pointer-chasing through scattered nodes that's cache-unfriendly. Open addressing stores every key directly in one fixed, pre-allocated array: no per-key allocation, contiguous memory that's cache-friendly, and a hard, known memory bound set at compile time. For a bare-metal system that bans the heap and needs deterministic memory, a fixed power-of-two table with linear probing fits naturally, you size it for the worst-case key count plus headroom so the load factor stays low. The one discipline open addressing adds is tombstone handling for deletion. And when the key space is small and dense, you skip hashing entirely for a direct-mapped table (array indexed by key), which is O(1) worst case with no collisions at all.
Data Structures & Algorithms · Interview question
Why does embedded code usually prefer open addressing over chaining?
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From the lesson
Hash Tables
O(1)-average keyed lookup by mapping keys to array slots: collisions, load factor, and why open addressing into a fixed array beats chaining when you have no heap.