在Erlang的许多进程中创建列表 [英] Create list across many processes in Erlang

问题描述

好的，我甚至很难想像如何描述我需要的东西。但这真的很简单。我想产生n个生成n个ID的进程。我有一些简单的递归和打印到终端。我正在努力创建一个列表可以访问每个这些生成的进程，我可以积累ids。那么，当进程完成后，我需要打印出任何副本。

我尝试了几个不同的选项与ets表，它总是打印一个没有列表。我认为是因为在进程完成之前我已经得到了打印功能？我知道我在想这个错误，但是会非常感谢在正确的方向微调。

解决方案

你需要同步你的主过程与产生的进程。您可以通过从每个id生成器进程发送消息到主服务器，并且后者将等待所有进程报告。

  master（N） - > 
 %%我们需要一个这个过程的一个pid来为奴隶发送消息到
 Self = self（），
 
 %%生成从属进程并保存其pids 
 Pids = [spawn（fun（） - > slave（Self）end || list：seq（1，N）]，
 
 %%从每个从属进程接收id消息
 Ids = [recv_id（Pid）|| Pid<  -  Pids]，
 
 %%使用这里的数据做任何我们想要的数据
 find_duplicates（Ids）
 
 slave（Master） - > 
 Id = mk_id（），
 
 %%向master发送消息
 Master！{id，self（），Id 
 
 recv_id（Pid） - > 
接收
 {id，Pid，Id}  - > Id 
 end。
 
 mk_id（） - > ... 
 find_duplicates（Ids） - > ... 
  

Ok, I am even having a hard time thinking of how to describe what I need. But it is really quite simple. I want to spawn n number of processes that generate n number of IDs. I have this working with some simple recursion and printing to the terminal. Where I am struggling is creating a list accessible to each of these spawned processes where I can accumulate the ids. then, when the processes are complete, I need to print-out any duplicates.

I tried a few different options with ets tables and it always prints a list of nothing. I presume because I get to the printing function before the processes have completed? I know I am thinking of this wrong but would greatly appreciate a nudge in the right direction.

解决方案

You need to synchronize your main process with the spawned processes. You can do that by sending a message from each of the id generator processes to the main, and the latter would wait for all the processes to report.

master(N) ->
   %% we need a pid of this process for the slaves to send messages to
   Self = self(),

   %% spawn slave processes and save their pids
   Pids = [spawn(fun() -> slave(Self) end || lists:seq(1, N)],

   %% receive id message from each of the slave processes
   Ids = [recv_id(Pid) || Pid <- Pids],

   %% do whatever we want with the data here
   find_duplicates(Ids).

slave(Master) ->
   Id = mk_id(),

   %% send a message to the master
   Master ! {id, self(), Id}.

recv_id(Pid) ->
   receive
      {id, Pid, Id} -> Id
   end.

mk_id() -> ...
find_duplicates(Ids) -> ...

这篇关于在Erlang的许多进程中创建列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！