Implement fastpair (#142)

* initial fastpair implementation
* FastPair initial implementation
* implement fastpair
* Add random test
* Add bench for fastpair
* Refactor with constructor for FastPair
* Add serialization for PairwiseDistance
* Add fp_bench feature for fastpair bench

Cargo.toml

@@ -17,6 +17,7 @@ default = ["datasets"]
 ndarray-bindings = ["ndarray"]
 nalgebra-bindings = ["nalgebra"]
 datasets = []
+fp_bench = []
 
 [dependencies]
 ndarray = { version = "0.15", optional = true }
@@ -26,6 +27,7 @@ num = "0.4"
 rand = "0.8"
 rand_distr = "0.4"
 serde = { version = "1", features = ["derive"], optional = true }
+itertools = "0.10.3"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 getrandom = { version = "0.2", features = ["js"] }
@@ -46,3 +48,8 @@ harness = false
 name = "naive_bayes"
 harness = false
 required-features = ["ndarray-bindings", "nalgebra-bindings"]
+
+[[bench]]
+name = "fastpair"
+harness = false
+required-features = ["fp_bench"]