Process Info Checker - v3

pi.erl

-module(pi).

-format #{paper => 80}.

-export([check/0]).

check() ->
    Pid = spawn(fun wait/0),
    erlang:yield(),

    Items =
        [backtrace, binary, catchlevel, current_function, current_location,
         current_stacktrace, dictionary, error_handler, garbage_collection,
         garbage_collection_info, group_leader, heap_size, initial_call, links,
         last_calls, memory, message_queue_len, messages, min_heap_size,
         min_bin_vheap_size, monitored_by, monitors, message_queue_data,
         priority, reductions, registered_name, sequential_trace_token,
         stack_size, status, suspending, total_heap_size, trace, trap_exit],
    CostlyBits = [Item || Item <- Items, reduction_increase(Item, Pid) > 0],
    [{reductions, R1} | _] = erlang:process_info(Pid, [reductions | CostlyBits]),
    [{reductions, R2} | _] = erlang:process_info(Pid, [reductions | CostlyBits]),
    Pid ! stop,
    R2 - R1.

reduction_increase(Item, Pid) ->
    [{reductions, R1}, {Item, Value}] =
        erlang:process_info(Pid, [reductions, Item]),
    [{reductions, R2}, {Item, Value}] =
        erlang:process_info(Pid, [reductions, Item]),
    R2 - R1.

wait() ->
    receive
        stop ->
            ok
    end.