有人可以用Erlang解释Pid(进程标识符)的结构吗? [英] Can someone explain the structure of a Pid (Process Identifier) in Erlang?
问题描述
有人可以用Erlang解释Pid的结构吗?
Can someone explain the structure of a Pid in Erlang?
ID如下所示: <A.B.C> ，例如< 0.30.0>，但是我想知道这三个位"(A，B和C)的含义.
Pids looks like this : <A.B.C> , e.g. <0.30.0> , but i would like to know what is the meaning of these three "bits" : A, B and C.
"A"在本地节点上似乎始终为0，但是当Pid的所有者位于另一个节点上时，此值会更改.
'A' seems to be always 0 on a local node, but this value changes when the Pid's owner is located on another node.
是否可以仅使用Pid在远程节点上直接发送消息?那样的东西:< 4568.30.0>！ Message，而不必显式指定注册进程的名称和节点名称({proc_name，Node}！Message)?
Is it possible to directly send a message on a remote node using only the Pid ? Something like that : <4568.30.0> ! Message , without having to explicitely specify the name of the registered process and the node name ( {proc_name, Node} ! Message ) ?
推荐答案
打印的进程ID< ABC>由 6 :
Printed process ids < A.B.C > are composed of 6:
- A, the node number (0 is the local node, an arbitrary number for a remote node)
- B, the first 15 bits of the process number (an index into the process table) 7
- C, bits 16-18 of the process number (the same process number as B) 7
内部，在32位仿真器上，进程号为28位宽. B和C的奇怪定义来自R9B和早期版本的Erlang，其中B是一个15位的进程ID，当达到最大进程ID并重用了较低的ID时，C是一个包装计数器递增.
Internally, the process number is 28 bits wide on the 32 bit emulator. The odd definition of B and C comes from R9B and earlier versions of Erlang in which B was a 15bit process ID and C was a wrap counter incremented when the max process ID was reached and lower IDs were reused.
在erlang分布中，PID稍大一些，因为它们包括节点原子以及其他信息. (分布式PID格式)
In the erlang distribution PIDs are a little larger as they include the node atom as well as the other information. (Distributed PID format)
当内部PID从一个节点发送到另一个节点时，它会自动转换为外部/分布式PID形式，因此，当一个节点上的<0.10.0>(inet_db)可能以<2265.10.0>结尾发送到另一个节点.您可以照常发送给这些PID.
When an internal PID is sent from one node to the other, it's automatically converted to the external/distributed PID form, so what might be <0.10.0> (inet_db) on one node might end up as <2265.10.0> when sent to another node. You can just send to these PIDs as normal.
% get the PID of the user server on OtherNode
RemoteUser = rpc:call(OtherNode, erlang,whereis,[user]),
true = is_pid(RemoteUser),
% send message to remote PID
RemoteUser ! ignore_this,
% print "Hello from <nodename>\n" on the remote node's console.
io:format(RemoteUser, "Hello from ~p~n", [node()]).
有关更多信息，请参见:内部PID结构， 节点创建信息， 与EPMD的节点创建计数器交互
For more information see: Internal PID structure, Node creation information, Node creation counter interaction with EPMD
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