ZENOTME commented on PR #45:
URL: https://github.com/apache/datasketches-rust/pull/45#issuecomment-3699372217
> Since it's not a 1:1 mapping, may you describe the concept and struct
mapping details?
In C++ and Java, the class hierarchy of the theta sketch looks like this:
```
- ThetaSketch
|--- UpdateThetaSketch (extend with update method)
|--- In Java, it has more implementation classes
|--- CompactThetaSketch (extend with serialize/deserialize method)
|--- ...
```
In Rust it doesn't have inheritance. So we only have two types:
```
- ThetaSketch: mutable
- CompactThetaSketch: mutable
```
For implementation, in C++, `update_theta_sketch_alloc` uses
`theta_update_sketch_base` as a hash table. I don't know why it's called
`xxx_base`, it looks like it doesn't have inheritance. And that's why I refer
to this class and rename it as `ThetaHashTable`.
For implementation in Java, it has more than one implementation inheriting
from UpdateThetaSketch: DirectQuickSelectSketch,
ConcurrentDirectQuickSelectSketch, and HeapAlphaSketch... There are different
ways to abstract the implementation: ThetaSketch<T> or wrap it as Box<dyn xxx>
internally.
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