• ref2401 (8/8) Jan 10 2015 I learned how 'atomicOp' and 'cas' work and why i need them from
• John Colvin (7/15) Jan 10 2015 I seem to be posting this a few times a week now:
• ref2401 (8/8) Jan 12 2015 Thanks for the links.
• John Colvin (13/21) Jan 12 2015 synchronized uses locks, and as such is good for (rule-of-thumb)

"ref2401" <refactor24 gmail.com> writes:

I learned how 'atomicOp' and 'cas' work and why i need them from 
the following sources:
http://ddili.org/ders/d.en/concurrency_shared.html (Ali's book)
http://www.informit.com/articles/article.aspx?p=1609144 (Andrei's 
book)

Can anybody tell me how 'atomicFence', 'atomicLoad' and 
'atomicStore' work and what do i need them for? Unfortunately 
official documentation didn't make it clear for me.

"John Colvin" <john.loughran.colvin gmail.com> writes:

On Saturday, 10 January 2015 at 12:16:24 UTC, ref2401 wrote:
 I learned how 'atomicOp' and 'cas' work and why i need them 
 from the following sources:
 http://ddili.org/ders/d.en/concurrency_shared.html (Ali's book)
 http://www.informit.com/articles/article.aspx?p=1609144 
 (Andrei's book)

 Can anybody tell me how 'atomicFence', 'atomicLoad' and 
 'atomicStore' work and what do i need them for? Unfortunately 
 official documentation didn't make it clear for me.

I seem to be posting this a few times a week now: 
http://channel9.msdn.com/Shows/Going+Deep/Cpp-and-Beyond-2012-Herb-Sutter-a
omic-Weapons-1-of-2 
and 
http://channel9.msdn.com/Shows/Going+Deep/Cpp-and-Beyond-2012-Herb-Sutter-atomic-Weapons-2-of-2

Although we don't have std::atomic in D, the same principles 
apply to using core.atomic.atomicLoad and friends.

"ref2401" <refactor24 gmail.com> writes:

Thanks for the links.

I have shared class instance. There are two threads which can 
read/write fields of the class. As i understand i can declare 
class as synchronized or i can read/write using 
atomicLoad/atomicStore.
What's the difference between these two approaches?
In what circumstances should i consider synchronized classes or 
using std.atomic?

"John Colvin" <john.loughran.colvin gmail.com> writes:

On Monday, 12 January 2015 at 13:37:19 UTC, ref2401 wrote:
 Thanks for the links.

 I have shared class instance. There are two threads which can 
 read/write fields of the class. As i understand i can declare 
 class as synchronized or i can read/write using 
 atomicLoad/atomicStore.
 What's the difference between these two approaches?
 In what circumstances should i consider synchronized classes or 
 using std.atomic?

synchronized uses locks, and as such is good for (rule-of-thumb) 
low contention situations, i.e. you don't have lots of threads 
all trying to access the same data at the same time (or few 
threads doing lots of repeated access). It has significant 
overhead as there is a cost to taking and releasing the lock and 
can be very slow under high-contention. Its advantage is that 
it's merely difficult to get right.

Using core.atomic and lock-free techniques in general is great 
for getting good performance in high-contention situations and/or 
reducing overhead in low-contention environments. However, it is 
very difficult to get right, very difficult to know if you have 
got it right and insanely difficult to debug when things go wrong.