Algorithm Selection

Downstream offers three core site selection algorithms. Each one curates a different temporal distribution of stored items while preserving the constant-space property of a traditional ring buffer.

Algorithm	Distribution	Typical use case
Steady	Uniform spacing across the entire stream	Trend analysis or when every time period matters
Stretched	Density thins with depth in the stream	Emphasize initial conditions or ancient history
Tilted	Density thins with item age	Recent-history monitoring

Hybrid variants combine multiple algorithms by partitioning the buffer.

All algorithms share the same interface. However, naive stretched and tilted algorithms have ingest limits of up to 2**S - 2 items, where S is the surface size. You can test limits programmatically using *_algo.has_ingest_capacity or *_algo.get_ingest_capacity.

For more details on algorithm behavior and guarantees, see our paper on the underlying algorithms. For hstrat users, analysis of how algorithm choice affects phylogeny reconstruction is available here.