Re: SDL-News: Communication between processes in different blocks

Subject: Re: SDL-News: Communication between processes in different blocks
From: Elie Cohen (cohen#verilogusa.com)
Date: Wed Aug 19 1998 - 01:05:45 GMT

I suddenly realize that the answer I gave Sergio did not make it to the newsgroup.
 
Here it is.
  

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Hello Sergio,

The problem you pose is interesting and very common indeed.

Here is an MSC description of how to solve this situation, as well as an SDL model I checked with the ObjectGEODE simulator.

At the end of this sequence, each one of the 4 processes knows all 4 PIDs, and can communicate with anyone.

The 2 difficulties you face are

1/ Non determinism: you solve the problem by starting with just 1 instance of each process on each block (p1.1 and p2.1). While you have only 1 instance, you can have them talk to each other without risk of non-determinism. Once the 1st instances know about each other, they can create themselves an offspring on each side (p1.2 and p2.2) and let their peer know their offspring (mychild) and their offpring share that information (yourpeer).

2/ How does the 1st instance of a process behave in a different manner from the 2nd instance: the trick is to notice that the 1st instance is created by the so called "meta process" and the PARENT operator returns NULL, whereas the 2nd instance has the 1st as its parent.

Let me know if I can help
 
Elie
 

----
Elie Cohen / Engineering Manager / cohen#verilogusa.com / tel: 972 241 6595 x13
VERILOG, Inc. / 3010 LBJ Fwy, Suite 900 / Dallas TX 75234 / tel: 800 424 3095 / fax: 972 241 6494
http://www.verilogusa.com
--------------------------------
Come and see us at the RTC Show,Sept 3, Dallas, TX.
For more information see www.rtcgroup.com
I suddenly realize that the answer I gave Sergio did not make it to the newsgroup.
 
Here it is.
 
----
 
Hello Sergio,
 
The problem you pose is interesting and very common indeed.
 
Here is an MSC description of how to solve this situation, as well as an SDL model I checked with the ObjectGEODE simulator.
 
 
At the end of this sequence, each one of the 4 processes knows all 4 PIDs, and can communicate with anyone.
 
The 2 difficulties you face are
 
1/ Non determinism: you solve the problem by starting with just 1 instance of each process on each block (p1.1 and p2.1). While you have only 1 instance, you can have them talk to each other without risk of non-determinism. Once the 1st instances know about each other, they can create themselves an offspring on each side (p1.2 and p2.2) and let their peer know their offspring (mychild) and their offpring share that information (yourpeer).
 
2/ How does the 1st instance of a process behave in a different manner from the 2nd instance: the trick is to notice that the 1st instance is created by the so called "meta process" and the PARENT operator returns NULL, whereas the 2nd instance has the 1st as its parent.
 
Let me know if I can help
 
Elie
 
 
 
----
Elie Cohen / Engineering Manager / cohen#verilogusa.com / tel: 972 241 6595 x13
VERILOG, Inc. / 3010 LBJ Fwy, Suite 900 / Dallas TX 75234 / tel: 800 424 3095 / fax: 972 241 6494
http://www.verilogusa.com
--------------------------------
Come and see us at the RTC Show,Sept 3, Dallas, TX.
For more information see www.rtcgroup.com
 
 

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