riak / apps / erlang_js / src / js_benchmark.erl

%% @author Kevin Smith <>
%% @copyright 2009-2010 Basho Technologies
%%    Licensed under the Apache License, Version 2.0 (the "License");
%%    you may not use this file except in compliance with the License.
%%    You may obtain a copy of the License at
%%    Unless required by applicable law or agreed to in writing, software
%%    distributed under the License is distributed on an "AS IS" BASIS,
%%    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%%    See the License for the specific language governing permissions and
%%    limitations under the License.

%% @doc Utility module for measuring latencies across the Erlang/Javascript
%% boundary. This module implements a very simple benchmark of defining and
%% executing a simple Javascript function 1000, 10000, and 100000 times.


-define(COUNTS, [1000, 10000, 100000]).


%% @spec run() -> list(int(), int(), int())
%% @doc Runs the benchmark and returns the average time to
%% process a function call for each set of iterations in
%% microseconds.
run() ->
    {ok, Ctx} = js_driver:new(),
    js:define(Ctx, <<"function add(x, y) { return x + y; }">>, []),
    Result = [time_calls(Ctx, Count) || Count <- ?COUNTS],

%% @private
time_calls(Ctx, Count) ->
    io:format("Starting: ~p~n", [Count]),
    Start = erlang:now(),
    do_calls(Ctx, Count),
    timer:now_diff(erlang:now(), Start) / Count.

%% @private
do_calls(_Ctx, 0) ->
do_calls(Ctx, Count) ->
    CorrectResult = Count * 2,
    {ok, CorrectResult} = js:call(Ctx, "add", [Count, Count]),
    do_calls(Ctx, Count - 1).
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