# Refinement

> USearch for Java

Refinement re-selects the neighbors of every stored entry against the finished graph, improving edges that were chosen when the graph around them was still incomplete.
It is a build step rather than a repair: a cheap insertion pass followed by one refinement reaches a better graph, in less total time, than a single expensive insertion pass, so a wide expansion factor belongs here rather than in `insert`.
It answers a `RefineReport` of the nodes re-selected and changed, the islands found and reconnected, and the `reachability` audit closing the heal.
Re-selecting a settled node changes nothing, so a caller loops until `changed` falls below whatever rate it considers settled.

```java
DenseRefineConfig wide = new DenseRefineConfig().expansionFactor(256);
while (index.on(pool).refine(wide).changed() > index.describe().size() / 100) {}
```

### Absorbing & Splitting

`absorb` appends donor indexes one after another, keeping their graphs and linking each in across the appended part, rather than re-inserting their vectors.
Every donor refuses every verb until the call is final; each one absorbed then stays closed, while one it did not absorb, like a donor of another scalar, is a live index again that you still own, though its entries may already have moved.
`split` is its inverse: the entries are partitioned along the graph into empty receivers, leaving the source empty and live.
Both answer a `RefineReport` of their closing refinements.

```java
index.on(pool).absorb(shard0, shard1);  // both donors are closed from here on
index.on(pool).split(new DenseSplitConfig().seed(7), left, right);  // two empty receivers take a part each
```