Re: Good practice for an approximation algorithm with start & stop features

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From: TT (Tom Tempelaere) (_N_0SPA|/\|titi_____at_hotmail.com|/\|APS0_N_)
Date: 04/02/04 

Date: Fri, 2 Apr 2004 06:01:09 -0800

Hi Jon,

I do not wish to reopen this discussion. But I was just browsing through IDesign's C# coding standard (v1.81) <http://www.idesign.net/idesign/download/IDesign%20CSharp%20Coding%20Standard.zip> and read the following guideline 4.4.19 (p20):

  "Do not use volatile variables, ..."

Notice that Juval doesn't write "Avoid ...". He should probably have said "Avoid".

Tom.

     ----- Jon Skeet [C# MVP] wrote: -----
     
     TT (Tom Tempelaere) <"=?Utf-8?B?VFQgKFRvbSBUZW1wZWxhZXJlKQ==?=" <_N_
     0SPA|/\|titi____@hotmail.com|/\|APS0_N_>> wrote:
> What you say is true, and I agree with you. Perhaps I'm still
> struggling too much with my c++ background. But I will have to take
> extra care not to mix the C# volatile with volatile in C/C++ when I
> have to do another project in C++. But that is part of the job I
> guess. I have to constantly be aware of these issues, because I'm
> dealing with different languages all the time. Another fact is that a
> lot of C# coders have a C++ background, and it is worth mentioning
> the difference of volatile in these languages because the languages look
> similar. That's why I mentioned it.
     
     Right. However, treating *anything* as the same between two languages
     is a potential problem. That's why I rigorously try to stick with the
     idioms, naming conventions etc of a new language - it helps me to think
     in that language, rather than one which happens to look like it :)
     
> I do (of course) hide any specifics of the event to the client, so
> that is not an issue. Asking the thread to finish is just calling a
> method, checking whether shutdown was requested is just another. Then
> one can implement it like he wants.
>> The event stopRunning or the bool stopRunning would have the same
> name. I agree that testing a boolean is more readable than waiting.
     
     Right.
      
> When you speak of locking, you mean that you would use a locking
> object to access the boolean instead of making it volatile? Like:
>> Object lockObject = new Object();
> bool stopRunning = false;
>> // signal:
> lock( lockObject ) { stopRunning= true; }
>> // check signal
> lock( lockObject ) { if(stopRunning) {...}}
>> Or did I get you wrong?
     
     Nope, that's exactly it. I'd put the actual lock within the property,
     but yes, that's the thing. The semantics of "lock" include a read
     memory barrier when acquiring, and a write memory barrier when
     releasing, so that you get volatile behaviour.
     
     --
     Jon Skeet - <skeet@pobox.com>
     http://www.pobox.com/~skeet
     If replying to the group, please do not mail me too
     

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