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CCHash now uses murmur hash
This commit is contained in:
Simon Cruanes
parent
ef06d117cb
commit
fcd2085190
2 changed files with 76 additions and 52 deletions
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@ -25,51 +25,66 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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(** {1 Hash combinators} *)
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type t = int
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type 'a hash_fun = 'a -> t
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type t = int64
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type 'a hash_fun = 'a -> t -> t
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let combine hash i =
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(hash * 65599 + i) land max_int
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let _r = 47
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let _m = 0xc6a4a7935bd1e995L
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let (<<>>) = combine
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let init = _m (* TODO? *)
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let hash_int i = combine 0 i
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(* combine key [k] with the current state [s] *)
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let _combine s k =
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let k = Int64.mul _m k in
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let k = Int64.logxor k (Int64.shift_right k _r) in
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let k = Int64.mul _m k in
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let s = Int64.logxor s k in
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let s = Int64.mul _m s in
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s
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let hash_int2 i j = combine i j
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let finish s =
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let s = Int64.logxor s (Int64.shift_right s _r) in
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let s = Int64.mul s _m in
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let s = Int64.logxor s (Int64.shift_right s _r) in
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(Int64.to_int s) land max_int
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let hash_int3 i j k = combine (combine i j) k
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let apply f x = finish (f x init)
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let hash_int4 i j k l =
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combine (combine (combine i j) k) l
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(** {2 Combinateurs} *)
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let rec hash_list f h l = match l with
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| [] -> h
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| x::l' -> hash_list f (combine h (f x)) l'
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let int_ i s = _combine s (Int64.of_int i)
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let bool_ x s = _combine s (if x then 1L else 2L)
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let char_ x s = _combine s (Int64.of_int (Char.code x))
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let int32_ x s = _combine s (Int64.of_int32 x)
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let int64_ x s = _combine s x
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let nativeint_ x s = _combine s (Int64.of_nativeint x)
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let string_ x s =
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let s = ref s in
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String.iter (fun c -> s := char_ c !s) x;
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!s
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let hash_array f h a =
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let h = ref h in
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Array.iter (fun x -> h := combine !h (f x)) a;
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!h
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let rec list_ f l s = match l with
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| [] -> s
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| x::l' -> list_ f l' (f x s)
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let hash_string s = Hashtbl.hash s
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let array_ f a s = Array.fold_right f a s
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let hash_pair h1 h2 (x,y) = combine (h1 x) (h2 y)
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let hash_triple h1 h2 h3 (x,y,z) = (h1 x) <<>> (h2 y) <<>> (h3 z)
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let pair h1 h2 (x,y) s = h2 y (h1 x s)
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let triple h1 h2 h3 (x,y,z) s = h3 z (h2 y (h1 x s))
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type 'a sequence = ('a -> unit) -> unit
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type 'a gen = unit -> 'a option
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type 'a klist = unit -> [`Nil | `Cons of 'a * 'a klist]
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let hash_seq f h seq =
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let h = ref h in
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seq (fun x -> h := !h <<>> f x);
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!h
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let seq f seq s =
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let s = ref s in
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seq (fun x -> s := f x !s);
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!s
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let rec hash_gen f h g = match g () with
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| None -> h
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| Some x ->
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hash_gen f (h <<>> f x) g
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let rec gen f g s = match g () with
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| None -> s
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| Some x -> gen f g (f x s)
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let rec hash_klist f h l = match l () with
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| `Nil -> h
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| `Cons (x,l') -> hash_klist f (h <<>> f x) l'
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let rec klist f l s = match l () with
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| `Nil -> s
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| `Cons (x,l') -> klist f l' (f x s)
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@ -25,40 +25,49 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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(** {1 Hash combinators}
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Combination of hashes based on the
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SDBM simple hash (see for instance
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{{:http://www.cse.yorku.ca/~oz/hash.html} this page})
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Combination of hashes based on the Murmur Hash (64 bits). See
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{{:https://sites.google.com/site/murmurhash/MurmurHash2_64.cpp?attredirects=0} this page}
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*)
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type t = int
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(** {2 Definitions} *)
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type 'a hash_fun = 'a -> t
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type t = private int64
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val combine : t -> t -> t
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(** Combine two hashes. Non-commutative. *)
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type 'a hash_fun = 'a -> t -> t
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(** Hash function for values of type ['a], merging a fingerprint of the
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value into the state of type [t] *)
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val (<<>>) : t -> t -> t
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(** Infix version of {!combine} *)
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val init : t
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(** Initial value *)
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val hash_int : int -> t
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val hash_int2 : int -> int -> t
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val hash_int3 : int -> int -> int -> t
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val hash_int4 : int -> int -> int -> int -> t
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val finish : t -> int
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(** Extract a usable hash value *)
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val hash_string : string -> t
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val apply : 'a hash_fun -> 'a -> int
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(** Apply a hash function to a value *)
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val hash_list : 'a hash_fun -> t -> 'a list hash_fun
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(** {2 Basic Combinators} *)
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val bool_ : bool hash_fun
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val char_ : char hash_fun
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val int_ : int hash_fun
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val string_ : string hash_fun
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val int32_ : int32 hash_fun
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val int64_ : int64 hash_fun
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val nativeint_ : nativeint hash_fun
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val list_ : 'a hash_fun -> 'a list hash_fun
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(** Hash a list. Each element is hashed using [f]. *)
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val hash_array : 'a hash_fun -> t -> 'a array hash_fun
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val array_ : 'a hash_fun -> 'a array hash_fun
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val hash_pair : 'a hash_fun -> 'b hash_fun -> ('a * 'b) hash_fun
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val hash_triple : 'a hash_fun -> 'b hash_fun -> 'c hash_fun -> ('a * 'b * 'c) hash_fun
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val pair : 'a hash_fun -> 'b hash_fun -> ('a * 'b) hash_fun
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val triple : 'a hash_fun -> 'b hash_fun -> 'c hash_fun -> ('a * 'b * 'c) hash_fun
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type 'a sequence = ('a -> unit) -> unit
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type 'a gen = unit -> 'a option
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type 'a klist = unit -> [`Nil | `Cons of 'a * 'a klist]
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val hash_seq : 'a hash_fun -> t -> 'a sequence hash_fun
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val hash_gen : 'a hash_fun -> t -> 'a gen hash_fun
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val hash_klist : 'a hash_fun -> t -> 'a klist hash_fun
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val seq : 'a hash_fun -> 'a sequence hash_fun
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val gen : 'a hash_fun -> 'a gen hash_fun
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val klist : 'a hash_fun -> 'a klist hash_fun
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