Erlang 实践杂记-2
二、测试代码运行时间
1、场景描述
????都说Erlang牛逼，高性能，但是执行效率真的很高吗？这个倒真不见得，感兴趣的，可以去测试下每行Erlang代码的运行时间，你会发现，Erlang的执行效率不见得比C或者是C++高。
2、API函数
tc(Module,?Function,?Arguments)?->?{Time,?Value}
Types:
Module?=?module()
Function?=?atom()
Arguments?=?[term()]
Time?=?integer()
In?microseconds
Value?=?term()
Evaluates?apply(Module,?Function,?Arguments)?and?measures?the?elapsed?real?time?as?reported?by?os:timestamp/0.?Returns?{Time,?Value},?where?Time?is?the?elapsed?real?time?in?microseconds,?and?Value?is?what?is?returned?from?the?apply.
3、实例
????-module(myring).
-export([start/1,?start_proc/2]).
start(Num)?->
start_proc(Num,?self()).
start_proc(0,?Pid)?->
Pid?!?ok;
start_proc(Num,?Pid)?->
? ? NPid?=?spawn(?MODULE,?start_proc,?[Num-1,?Pid]),
NPid?!?ok,
receive?ok?->?ok?end.
???运行过程
Eshell?V5.9.1??(abort?with?^G)
1>?c(myring).
{ok,myring}
2>?timer:tc(myring,?start,?1000000).??????????%%Arguments?=?[term()]
**?exception?error:?bad?argument
?????in?function??apply/3
????????called?as?apply(myring,start,1000000)
?????in?call?from?timer:tc/3?(timer.erl,?line?194)
3>?timer:tc(myring,?start,?[1000000]).
{2375954,ok}?????????????????????%%时间单位为?us
4>?
