benchmark instance

bench.zig

@@ -9,12 +9,32 @@ const time = std.time;
 
 const Decl = std.builtin.TypeInfo.Declaration;
 
-pub fn benchmark(comptime B: type) !void {
+pub const Opts = struct {
+    min_iterations: usize = 10000,
+    max_iterations: usize = 100000,
+    max_time: usize = 500 * time.ns_per_ms,
+};
+
+pub fn benchmark(type_or_instance: anytype) !void {
+    switch (@typeInfo(@TypeOf(type_or_instance))) {
+        .Type => try run(type_or_instance, type_or_instance, null),
+        .Pointer => |p| try run(p.child, type_or_instance, null),
+        else => @compileError("Pass a type or a pointer/instance to a struct."),
+    }
+}
+
+pub fn run(comptime B: type, context: anytype, run_opts: ?Opts) !void {
     const args = if (@hasDecl(B, "args")) B.args else [_]void{{}};
     const arg_names = if (@hasDecl(B, "arg_names")) B.arg_names else [_]u8{};
-    const min_iterations = if (@hasDecl(B, "min_iterations")) B.min_iterations else 10000;
-    const max_iterations = if (@hasDecl(B, "max_iterations")) B.max_iterations else 100000;
-    const max_time = 500 * time.ns_per_ms;
+
+    var opts = Opts{};
+    if (run_opts) |ro| {
+        opts = ro;
+    } else {
+        if (@hasDecl(B, "min_iterations")) opts.min_iterations = B.min_iterations;
+        if (@hasDecl(B, "max_iterations")) opts.max_iterations = B.max_iterations;
+    }
+    opts.max_iterations = math.max(opts.min_iterations, opts.max_iterations);
 
     const functions = comptime blk: {
         var res: []const Decl = &[_]Decl{};
@@ -78,14 +98,14 @@ pub fn benchmark(comptime B: type) !void {
             var runtime_sum: u128 = 0;
 
             var i: usize = 0;
-            while (i < min_iterations or
-                (i < max_iterations and runtime_sum < max_time)) : (i += 1)
+            while (i < opts.min_iterations or
+                (i < opts.max_iterations and runtime_sum < opts.max_time)) : (i += 1)
             {
                 timer.reset();
 
                 const res = switch (@TypeOf(arg)) {
-                    void => @field(B, def.name)(),
-                    else => @field(B, def.name)(arg),
+                    void => @field(context, def.name)(),
+                    else => @field(context, def.name)(arg),
                 };
                 const runtime = timer.read();
                 runtime_sum += runtime;
@@ -244,3 +264,60 @@ test "benchmark generics" {
         }
     });
 }
+
+test "benchmark instance" {
+    const iterations: usize = 100000;
+    const args = [_][]const u8{ "01" };
+    const arg_names = [_][]const u8{ "01 x n" };
+
+    const capacity = args[0].len * iterations;
+    const BoundedArray = std.BoundedArray(u8, capacity);
+    const ArrayList = std.ArrayList(u8);
+    const allocator = std.testing.allocator;
+
+    var instance = (struct {
+        const args = args;
+        const arg_names = arg_names;
+        const min_iterations = iterations;
+        const max_iterations = iterations;
+
+        const Self = @This();
+        bounded_array: BoundedArray,
+        non_resizing_list: ArrayList,
+        resizing_list: ArrayList,
+
+        fn bounded_array_append_slice(self: *Self, data: []const u8) !void {
+            try self.bounded_array.appendSlice(data);
+        }
+        fn non_resizing_list_append_slice(self: *Self, data: []const u8) !void {
+            try self.non_resizing_list.appendSlice(data);
+        }
+        fn resizing_list_append_slice(self: *Self, data: []const u8) !void {
+            try self.resizing_list.appendSlice(data);
+        }
+    } {
+        .bounded_array = .{ .buffer = undefined, .len = 0 },
+        .non_resizing_list = ArrayList.init(allocator),
+        .resizing_list = ArrayList.init(allocator),
+    });
+    defer {
+        instance.non_resizing_list.deinit();
+        instance.resizing_list.deinit();
+    }
+
+    try instance.non_resizing_list.ensureTotalCapacity(capacity);
+
+    try benchmark(&instance);
+
+    // reset
+    instance.bounded_array.len = 0;
+    instance.non_resizing_list.clearRetainingCapacity();
+    instance.resizing_list.clearAndFree();
+
+    // run with fewer iterations
+    const fewer_iterations = iterations / 2;
+    try run(@TypeOf(instance), &instance, .{
+        .min_iterations = fewer_iterations,
+        .max_iterations = fewer_iterations,
+    });
+}