<div class="gmail_quote">On Fri, Jan 29, 2010 at 6:03 PM, Andrei Alexandrescu <span dir="ltr"><<a href="mailto:andrei@erdani.com">andrei@erdani.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Walter and I just talked over the phone and agreed on the following. Of course the decisions are not final and are up for debate.<br>
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1. Atomic array assignment is in.<br>
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We discussed that and concluded the following:<br>
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* CMPXCHG16B and friends are the norm of modern Intel-like machines, and are unlikely to go away soon. We are designing D for the future and the future looks like two-word assignment is in it.<br>
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* Pre-2004 AMDs and probably some other chips still lack two-word assignment. We decided that we will look for creative solutions to those problems as they come up (hat tip to Kevin's idea of using a spin lock).<br>
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2. Atomic assignment of real is still undecided.<br>
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I think I'll write in TDPL that it's platform dependent. Assignment to 80-bit reals on 32-bit machines is still problematic.<br>
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3. There are _no_ more synchronized or shared methods. That is, code like this is incorrect:<br>
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class A { void fun() shared { } }<br>
class B { void fun() synchronized { } }<br>
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Rationale: it is tenuous to offer mixed modes in the same class.<br>
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4. The "synchronized" attribute is hoisted at class level:<br>
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synchronized class A { ... }<br>
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That means each and every method of that class is synchronized.<br>
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5. The "shared" attribute is hoisted at class or struct level:<br>
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shared class A { ... }<br>
shared struct B { ... }<br>
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That means the implementation is lock-free and uses its own synchronization mechanisms.<br>
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6. When defining an object of a synchronized of shared type, you still need to qualify it with "shared" in order to make it so. For example:<br>
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synchronized class A { ... }<br>
shared A a; // fine<br>
A b; // error<br>
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(I'm not 100% sure about this.)<br>
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These rules will simplify and modularize concurrent code. With message passing, synchronized classes, and shared objects, I hope we get to put together a solid concurrency offering in D2. Please share your thoughts.<br>
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Andrei<br></blockquote><div><br>I like it.<br><br>Kevin<br><br><br> </div></div>