From f9ba2e8997b12ab39d0bba729caa165fa61f2122 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 19 Mar 2026 21:05:41 -0400
Subject: [PATCH] cleanup hash bench

---
 benchs/bench_hash.ml | 110 +++++++++++++++++--------------------------
 1 file changed, 42 insertions(+), 68 deletions(-)

diff --git a/benchs/bench_hash.ml b/benchs/bench_hash.ml
index 110f284c..4fc12bf2 100644
--- a/benchs/bench_hash.ml
+++ b/benchs/bench_hash.ml
@@ -1,7 +1,4 @@
 (** Benchmarks for CCHash primitives.
-
-    Run with: dune exec benchs/bench_hash.exe -- [options]
-    See: dune exec benchs/bench_hash.exe -- --help
 *)
 
 [@@@warning "-5"]
@@ -9,96 +6,73 @@
 module B = Benchmark
 
 let repeat = 3
-
-(* --- data setup ---------------------------------------------------------- *)
-
 let n_ints = 1_000
-
-let ints =
-  Array.init n_ints (fun i -> i * 2654435761 (* knuth multiplicative *))
-
-let short_str = String.make 16 'x'
-let medium_str = String.make 64 'x'
-let long_str = String.make 512 'x'
-
-(* Strings of various lengths with distinct content *)
-let strings_short = Array.init n_ints (fun i -> Printf.sprintf "%016d" i)
-let strings_medium = Array.init n_ints (fun i -> Printf.sprintf "%064d" i)
-
-(* --- benchmarks ---------------------------------------------------------- *)
+let ints = Array.init n_ints (fun i -> i * 2654435761)
 
 let bench_int_hash ~time () =
-  let r = ref 0 in
   B.throughputN time ~repeat
     [
-      "CCHash.int", (fun () -> Array.iter (fun x -> r := CCHash.int x) ints), ();
+      ( "CCHash.int",
+        (fun () ->
+          Array.iter
+            (fun x -> ignore @@ Sys.opaque_identity (CCHash.int x))
+            ints),
+        () );
       ( "Hashtbl.hash (poly)",
-        (fun () -> Array.iter (fun x -> r := Hashtbl.hash x) ints),
+        (fun () ->
+          Array.iter
+            (fun x -> ignore @@ Sys.opaque_identity (Hashtbl.hash x))
+            ints),
         () );
       ( "CCHash.int64",
         (fun () ->
-          Array.iter (fun x -> r := CCHash.int64 (Int64.of_int x)) ints),
+          Array.iter
+            (fun x ->
+              ignore @@ Sys.opaque_identity (CCHash.int64 (Int64.of_int x)))
+            ints),
         () );
-    ];
-  ignore !r
-
-let bench_string_hash ~time () =
-  let r = ref 0 in
-  B.throughputN time ~repeat
-    [
-      ( "CCHash.string/16",
-        (fun () -> Array.iter (fun s -> r := CCHash.string s) strings_short),
-        () );
-      ( "CCHash.string/64",
-        (fun () -> Array.iter (fun s -> r := CCHash.string s) strings_medium),
-        () );
-      "CCHash.string literal/16", (fun () -> r := CCHash.string short_str), ();
-      "CCHash.string literal/64", (fun () -> r := CCHash.string medium_str), ();
-      "CCHash.string literal/512", (fun () -> r := CCHash.string long_str), ();
-      ( "Hashtbl.hash/16",
-        (fun () -> Array.iter (fun s -> r := Hashtbl.hash s) strings_short),
-        () );
-    ];
-  ignore !r
+    ]
 
 let bench_combine64 ~time () =
-  let r = ref 0L in
   B.throughputN time ~repeat
     [
       ( "combine64 chain x5",
         (fun () ->
           Array.iter
             (fun x ->
-              r :=
-                CCHash.(
-                  combine64
-                    (combine64
-                       (combine64
-                          (combine64
-                             (combine64 seed (Int64.of_int x))
-                             (Int64.of_int (x lxor 0xaaaa)))
-                          (Int64.of_int (x + 1)))
-                       (Int64.of_int (x * 3)))
-                    (Int64.of_int (x lxor (x lsr 7)))))
+              ignore
+              @@ Sys.opaque_identity
+                   CCHash64.(
+                     combine2
+                       (combine2
+                          (combine2
+                             (combine2 (Int64.of_int x)
+                                (Int64.of_int (x lxor 0xaaaa)))
+                             (Int64.of_int (x + 1)))
+                          (Int64.of_int (x * 3)))
+                       (Int64.of_int (x lxor (x lsr 7)))))
             ints),
         () );
       ( "CCHash.list int [1..5]",
-        (fun () -> r := Int64.of_int CCHash.(list int [ 1; 2; 3; 4; 5 ])),
+        (fun () ->
+          Array.iter
+            (fun x ->
+              ignore
+              @@ Sys.opaque_identity
+                   (Int64.of_int
+                      CCHash.(list int [ x + 1; x + 2; x + 3; x + 4; x + 5 ])))
+            ints),
         () );
-    ];
-  ignore !r
+    ]
 
 (* --- tree for run_global ------------------------------------------------- *)
 
 let () =
-  B.Tree.add_global "hash"
-    B.Tree.(
-      "int"
-      @>> (fun () -> bench_int_hash ~time:2 ())
-      @> "string"
-      @>> (fun () -> bench_string_hash ~time:2 ())
-      @> "combine64"
-      @>> (fun () -> bench_combine64 ~time:2 ())
-      @> nil)
+  B.Tree.(
+    register @@ "hash"
+    @>>> [
+           "int" @> lazy (bench_int_hash ~time:2 ());
+           "combine64" @> lazy (bench_combine64 ~time:2 ());
+         ])
 
 let () = try B.Tree.run_global () with Arg.Help msg -> print_endline msg