mirror of
https://github.com/c-cube/ocaml-containers.git
synced 2025-12-06 03:05:28 -05:00
big changes in the Cache module, with clean signatures and several
functors that implement distinct policies
This commit is contained in:
Simon Cruanes
parent
56d8de46a3
commit
22e948e374
3 changed files with 222 additions and 69 deletions
214
cache.ml
214
cache.ml
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@ -23,66 +23,184 @@ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** an imperative cache for memoization of pairs *)
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(** {1 Memoization caches} *)
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module type S =
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sig
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type key
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module type EQ = sig
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type t
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val equal : t -> t -> bool
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end
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type 'a t
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module type HASH = sig
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include EQ
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val hash : t -> int
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end
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(** create a cache with given size *)
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val create : int -> (key -> key -> 'a) -> 'a t
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(** Signature of a cache for values *)
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module type S = sig
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type 'a t
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type key
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(** find a value in the cache *)
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val lookup : 'a t -> key -> key -> 'a
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val create : int -> 'a t
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(** Create a new cache of the given size. *)
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(** clear the cache from its content *)
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val clear : 'a t -> unit
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end
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val clear : 'a t -> unit
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(** Clear content of the cache *)
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module type CachedType =
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sig
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type t
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val hash : t -> int
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val equal : t -> t -> bool
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end
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val with_cache : 'a t -> (key -> 'a) -> key -> 'a
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(** Wrap the function with the cache *)
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end
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(** Signature of a cache for pairs of values *)
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module type S2 = sig
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type 'a t
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type key
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val create : int -> 'a t
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(** Create a new cache of the given size. *)
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val clear : 'a t -> unit
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(** Clear content of the cache *)
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val with_cache : 'a t -> (key -> key -> 'a) -> key -> key -> 'a
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(** Wrap the function with the cache *)
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end
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module Make(HType : CachedType) =
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struct
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type key = HType.t
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(** {2 Small linear cache} *)
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(** A slot of the array contains a (key, value, true)
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if key->value is stored there (at index hash(key) % length),
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(null, null, false) otherwise.
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(** This cache stores (key,value) pairs in an array, that is traversed
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linearily. It is therefore only reasonable for small sizes (like 5). *)
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The first slot in the array contains the function
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used to produce the value upon a cache miss. *)
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type 'a t = (key * key * 'a * bool) array
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module Linear(X : EQ) = struct
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type 'a t = 'a bucket array
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and 'a bucket = Empty | Pair of key * 'a
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and key = X.t
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let my_null = (Obj.magic None, Obj.magic None, Obj.magic None, false)
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let create size =
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assert (size >= 1);
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Array.create size Empty
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let set_fun c f = c.(0) <- Obj.magic f
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let clear cache =
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Array.fill cache 0 (Array.length cache) Empty
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let create size f =
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let c = Array.create (size+1) my_null in
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c.(0) <- Obj.magic f;
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c
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(** Insert the binding (x -> y) into the cache *)
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let insert cache x y =
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let n = Array.length cache in
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(* shift other values toward the end *)
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Array.blit cache 0 cache 1 (n-1);
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cache.(0) <- Pair(x,y)
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let lookup c k1 k2 =
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let i = (((HType.hash k1 + 17) lxor HType.hash k2) mod (Array.length c -1)) + 1 in
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match c.(i) with
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| (_, _, _, false) ->
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let v = ((Obj.magic c.(0)) : key -> key -> 'a) k1 k2 in
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c.(i) <- (k1, k2, v, true); v
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| (k1', k2', _, true) when not (HType.equal k1 k1') || not (HType.equal k2 k2')->
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let v = ((Obj.magic c.(0)) : key -> key -> 'a) k1 k2 in
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c.(i) <- (k1, k2, v, true); v
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| (_, _, v, true) -> v
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(** Try to find [f x] in the cache, otherwise compute it
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and cache the result *)
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let with_cache cache f x =
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let n = Array.length cache in
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let rec search i =
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(* function that performs the lookup *)
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if i = n then begin
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(* cache miss *)
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let y = f x in
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insert cache x y;
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y
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end else match cache.(i) with
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| Pair (x',y) when X.equal x x' -> y
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| Empty | Pair _ -> search (i+1)
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in
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search 0
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end
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let clear c =
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let f = c.(0) in
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Array.iteri (fun i _ -> c.(i) <- my_null) c;
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c.(0) <- f
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end
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module Linear2(X : EQ) = struct
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type 'a t = 'a bucket array
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and 'a bucket = Empty | Assoc of key * key * 'a
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and key = X.t
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let create size =
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assert (size >= 1);
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Array.create size Empty
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let clear cache =
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Array.fill cache 0 (Array.length cache) Empty
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(** Insert the binding (x -> y) into the cache *)
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let insert cache x1 x2 y =
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let n = Array.length cache in
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(* shift other values toward the end *)
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Array.blit cache 0 cache 1 (n-1);
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cache.(0) <- Assoc(x1,x2,y)
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(** Try to find [f x] in the cache, otherwise compute it
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and cache the result *)
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let with_cache cache f x1 x2 =
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let n = Array.length cache in
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let rec search i =
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(* function that performs the lookup *)
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if i = n then begin
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(* cache miss *)
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let y = f x1 x2 in
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insert cache x1 x2 y;
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y
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end else match cache.(i) with
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| Assoc (x1',x2',y) when X.equal x1 x1' && X.equal x2 x2' -> y
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| Empty | Assoc _ -> search (i+1)
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in
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search 0
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end
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(** {2 An imperative cache of fixed size for memoization of pairs} *)
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module Replacing(X : HASH) = struct
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type key = X.t
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(** A slot of the array contains a (key, value, true)
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if key->value is stored there (at index hash(key) % length),
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(null, null, false) otherwise.
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The first slot in the array contains the function
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used to produce the value upon a cache miss. *)
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type 'a t = 'a bucket array
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and 'a bucket = Empty | Assoc of key * 'a
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let create size =
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Array.create size Empty
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let clear c =
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Array.fill c 0 (Array.length c) Empty
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let with_cache c f x =
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let i = (X.hash x) mod (Array.length c) in
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match c.(i) with
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| Assoc (x', y) when X.equal x x' ->
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y (* cache hit *)
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| Assoc _ | Empty -> (* cache miss *)
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let y = f x in
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c.(i) <- Assoc (x, y);
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y
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end
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module Replacing2(X : HASH) = struct
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type key = X.t
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(** A slot of the array contains a (key, value, true)
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if key->value is stored there (at index hash(key) % length),
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(null, null, false) otherwise.
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The first slot in the array contains the function
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used to produce the value upon a cache miss. *)
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type 'a t = 'a bucket array
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and 'a bucket = Empty | Assoc of key * key * 'a
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let create size =
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Array.create size Empty
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let clear c =
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Array.fill c 0 (Array.length c) Empty
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let with_cache c f x1 x2 =
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let i = (((X.hash x1 + 17) lxor X.hash x2) mod Array.length c) in
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match c.(i) with
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| Assoc (x1', x2', y) when X.equal x1 x1' && X.equal x2 x2' ->
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y (* cache hit *)
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| Assoc _ | Empty -> (* cache miss *)
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let y = f x1 x2 in
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c.(i) <- Assoc (x1, x2, y);
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y
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end
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74
cache.mli
74
cache.mli
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@ -23,30 +23,64 @@ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** An imperative cache of fixed size for memoization of pairs *)
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(** {1 Memoization caches} *)
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module type S =
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sig
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type key
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(** {2 Signatures} *)
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type 'a t
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module type EQ = sig
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type t
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val equal : t -> t -> bool
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end
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(** create a cache with given size *)
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val create : int -> (key -> key -> 'a) -> 'a t
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module type HASH = sig
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include EQ
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val hash : t -> int
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end
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(** find a value in the cache *)
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val lookup : 'a t -> key -> key -> 'a
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(** Signature of a cache for values *)
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module type S = sig
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type 'a t
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type key
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(** clear the cache from its content *)
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val clear : 'a t -> unit
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end
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val create : int -> 'a t
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(** Create a new cache of the given size. *)
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module type CachedType =
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sig
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type t
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val hash : t -> int
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val equal : t -> t -> bool
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end
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val clear : 'a t -> unit
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(** Clear content of the cache *)
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val with_cache : 'a t -> (key -> 'a) -> key -> 'a
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(** Wrap the function with the cache *)
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end
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(** Signature of a cache for pairs of values *)
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module type S2 = sig
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type 'a t
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type key
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val create : int -> 'a t
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(** Create a new cache of the given size. *)
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val clear : 'a t -> unit
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(** Clear content of the cache *)
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val with_cache : 'a t -> (key -> key -> 'a) -> key -> key -> 'a
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(** Wrap the function with the cache *)
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end
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(** {2 Small linear cache} *)
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(** This cache stores (key,value) pairs in an array, that is traversed
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linearily. It is therefore only reasonable for small sizes (like 5). *)
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module Linear(X : EQ) : S with type key = X.t
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module Linear2(X : EQ) : S2 with type key = X.t
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(** {2 Hashtables that resolve collisions by replacing} *)
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module Replacing(X : HASH) : S with type key = X.t
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module Replacing2(X : HASH) : S2 with type key = X.t
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(* TODO LRU cache *)
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(** functorial implementation *)
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module Make(CType : CachedType) : S with type key = CType.t
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@ -8,6 +8,7 @@ let suite =
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Test_heap.suite;
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Test_graph.suite;
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Test_univ.suite;
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Test_cache.suite;
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]
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let _ =
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