Serialization

The path extension picks the layout: a .safegraphs path is one monolith, and a .safegraphs.json path is a manifest cataloging many.

index.on(&executor).save("index.safegraphs")?;
let loaded = DenseIndex::load_ram("index.safegraphs")?;
let gpu = unsafe { Executor::for_vram(&[0], None, &[], 0)? };
let placed = DenseIndex::load_vram(DenseLoadVramConfig {
    executor: Some(&gpu),
    devices: &[0],
    ..DenseLoadVramConfig::from("index.safegraphs")
})?;
let viewed = DenseIndex::view_ram("index.safegraphs")?;          // read-only, served from the mapping
let metadata = DenseIndex::metadata("index.safegraphs")?;        // geometry without loading a shard

Checkpoints are residency-portable: one file materializes into RAM, uploads to a device, or opens in place on disk, decided by the constructor that reads it. The metadata carries only the four fields a checkpoint froze, so values_per_key and the placement stay yours to set in the load config. view_ram answers Status::Unsupported until RAM shards can serve a mapping in place. A stopped save leaves leftovers every reader rejects, which are yours to remove.

In-memory buffers hold single monoliths only, through save_buffer, load_ram_buffer or load_vram_buffer, and metadata_buffer.

let mut arena = Arena::new_in(&executor)?;
let monolith = index.on(&executor).save_buffer(&mut arena)?;
let restored = DenseIndex::load_ram_buffer(monolith.view()?)?;