Thanks Saliya, this makes sense. It does solve the problem. Though it is not
high level construct like Java's 'synchronized", it is a small price to pay for
the benefit of no-deadlock guarantee.
The only concern now is, I have to make sure that the activity that sets inUse
will ultimately unset it. What I mean is, some exception may happen inside the
method, so I need to learn how to implement behavior similar to Java's
"finally" block.
________________________________
From: Saliya Ekanayake <esal...@gmail.com>
To: LEONID ILYEVSKY <leonidilyev...@yahoo.com>
Cc: Mailing list for users of the X10 programming language
<x10-users@lists.sourceforge.net>
Sent: Friday, November 16, 2012 11:51 AM
Subject: Re: [X10-users] Atomic blocks
A small correction to what I sent earlier. The last operation should be inside
an atomic block too.
when (! inUse) {
inUse = true;
}
m( ); // the time consuming operation
atomic {
inUse = false;
}
On Fri, Nov 16, 2012 at 11:47 AM, Saliya Ekanayake <esal...@gmail.com> wrote:
Btw. you may find the X10 language specification useful as
well http://x10.sourceforge.net/documentation/languagespec/x10-230.pdf
>
>
>Thanks,
>Saliya
>
>
>
>On Fri, Nov 16, 2012 at 11:45 AM, Saliya Ekanayake <esal...@gmail.com> wrote:
>
>Thank you, I see what you meant now.
>>
>>
>>Yes, it seems all atomic operations in one place is handled with an exclusive
>>lock. So as a workaround will something like this work,
>>
>>
>>In your class having a boolean variable, say inUse which is initially false.
>>Then you will implement your method without specifying as an atomic method,
>>say m( )
>>
>>
>>Now having an entry and exit atomic sections like,
>>
>>
>>when (! inUse) {
>> inUse = true;
>>}
>>
>>
>>m( ); // the time consuming operation
>>inUse = false;
>>
>>
>>Thank you,
>>Saliya
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>On Fri, Nov 16, 2012 at 10:59 AM, LEONID ILYEVSKY <leonidilyev...@yahoo.com>
>>wrote:
>>
>>Saliya,
>>>
>>>
>>>Thanks for your reply.
>>>Let me clarify my question. This situation, I believe, is pretty common
>>>actually.
>>>
>>>
>>>So I have multiple objects of the same class. The methods are made
>>>synchronized because they update the objects' data based on the previous
>>>values and some information read from, let say, files or database. Such
>>>operation may take some time, and it is important that two different
>>>instances may be processed in parallel.
>>>On the other hand, if two threads try to update the same object, then only
>>>one at a time can be allowed, the other thread(s) must wait.
>>>So, in Java this is achieved simply by declaring methods synchronized, and
>>>then I safely can have a pool of threads doing the work, efficiently
>>>utilizing resources, and be sure that no data corruption happens.
>>>
>>>
>>>I am reading now http://www.cs.rice.edu/~vs3/PDF/pmup06.pdf , and it says
>>>that currently atomic behavior is implemented by an exclusive lock on the
>>>place. This means that parallel operation as described in my java example
>>>will be impossible in X10. I understand that this approach helps to make
>>>sure that deadlock never happens.
>>>
>>>
>>>However, real life applications may require more parallelizm. For example,
>>>the classical textbook banking application. I withdraw my money from the
>>>ATM, at the same time the back office application is trying to apply direct
>>>deposit to my account. These operations must be syncronized, but operations
>>>on othe client's accounts can be applied at the same time, they don't have
>>>to wait.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>________________________________
>>> From: Saliya Ekanayake <esal...@gmail.com>
>>>To: LEONID ILYEVSKY <leonidilyev...@yahoo.com>; Mailing list for users of
>>>the X10 programming language <x10-users@lists.sourceforge.net>
>>>Sent: Friday, November 16, 2012 10:38 AM
>>>Subject: Re: [X10-users] Atomic blocks
>>>
>>>
>>>
>>>Hi Leonid,
>>>
>>>
>>>In your java version, are the threads accessing a separate copy of your
>>>object? If so it seems like it should work even without being a synchronized
>>>method. Also, if you create multiple objects and access them from separate
>>>activities in X10 they should not block and atomic may not make any
>>>difference as I understand.
>>>
>>>
>>>In fact, atomic usage is beneficial only when you have a critical section
>>>that at a given time only one activity is allowed to be in (per place).
>>>
>>>
>>>Hope this helps.
>>>
>>>
>>>Thank you,
>>>Saliya
>>>
>>>
>>>
>>>On Fri, Nov 16, 2012 at 10:28 AM, LEONID ILYEVSKY <leonidilyev...@yahoo.com>
>>>wrote:
>>>
>>>Hi,
>>>>
>>>>
>>>>I am new to X10, and I have a question about the atomic construct, maybe
>>>>somebody can clarify it for me.
>>>>
>>>>
>>>>Let say, in Java I have a class with some synchronized (on the object
>>>>level) methods. If I have 100 such objects in memory, then 100 threads can
>>>>simultaneously work on those objects without blocking each other.
>>>>How you do the same thing in X10 (asuming the program is running in one
>>>>place)? From the definition of the atomic block, it seems that if I
>>>>translate Java syncronized methods to X10 atomic methods, then only one
>>>>object at a time can be processed. Is my understanding correct?
>>>>
>>>>------------------------------------------------------------------------------
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>>>>
>>>>
>>>
>>>
>>>
>>>--
>>>Saliya Ekanayake
>>>http://www.esaliya.blogspot.com
>>>http://www.esaliya.wordpress.com
>>>
>>>
>>>
>>
>>
>>
>>--
>>Saliya Ekanayake
>>http://www.esaliya.blogspot.com
>>http://www.esaliya.wordpress.com
>>
>
>
>
>--
>Saliya Ekanayake
>http://www.esaliya.blogspot.com
>http://www.esaliya.wordpress.com
>
--
Saliya Ekanayake
http://www.esaliya.blogspot.com
http://www.esaliya.wordpress.com------------------------------------------------------------------------------
Monitor your physical, virtual and cloud infrastructure from a single
web console. Get in-depth insight into apps, servers, databases, vmware,
SAP, cloud infrastructure, etc. Download 30-day Free Trial.
Pricing starts from $795 for 25 servers or applications!
http://p.sf.net/sfu/zoho_dev2dev_nov
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