# HyperLogLog

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HyperLogLog is a probabilistic algorithm for estimating the number of
*distinct* elements (*cardinality*) of a multiset. Several variations of the
original algorithm, described by P. Flajolet et al., have been proposed.

The following implementations are provided:

- [HyperLogLog](http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf)
- [HyperLogLog++](https://research.google/pubs/pub40671/)


## Usage

Add to `Cargo.toml`:

```toml
[dependencies]
hyperloglogplus = "*"
```

With Rust compiler version 1.45.0 or higher consider enabling the `const-loop`
feature for better performance, see [here](https://github.com/tabac/hyperloglog.rs/pull/3) 
for more details.

```toml
[dependencies]
hyperloglogplus = { version = "*", features = ["const-loop"] }
```


A simple example using HyperLogLog++ implementation:

```rust
use std::collections::hash_map::RandomState;
use hyperloglogplus::{HyperLogLog, HyperLogLogPlus};

let mut hllp: HyperLogLogPlus<u32, _> =
    HyperLogLogPlus::new(16, RandomState::new()).unwrap();

hllp.insert(&12345);
hllp.insert(&23456);

assert_eq!(hllp.count().trunc() as u32, 2);

```

## Evaluation

[Here](evaluation/) you can find figures and discussion on experimental evaluation.