On Tue, Jul 20, 2010 at 3:36 AM, Eray Ozkural <span dir="ltr">&lt;<a href="mailto:examachine@gmail.com">examachine@gmail.com</a>&gt;</span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div class="im">On Mon, Jul 12, 2010 at 4:19 PM, Gaspard Bucher <span dir="ltr">&lt;<a href="mailto:gaspard@teti.ch" target="_blank">gaspard@teti.ch</a>&gt;</span> wrote:<br></div><div class="gmail_quote"><div class="im">
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
 Just a final question on the topic: has JoCaml anything to do with<br>
this concurrency (shared memory) question ?<font color="#888888"></font></blockquote></div><div><br>It seems to me that it can be implemented for a shared memory system. Why not? But it&#39;s been designed with distributed memory in mind. So, I suppose writing to shared memory could be slow. It&#39;d be sort of like implementing synchronization on top of a message passing system. Although I can see that reading is OK.<br>
</div></div></blockquote></div><br clear="all">On second thought it&#39;s not so clear how reads could be efficient. I&#39;d assumed that somehow messages could be sent without making a separate copy of the data, so in principle we could perform the reads just as fast. Interesting question, though, thanks Gaspard. Now I realized it&#39;s not so clear and I apologize for that mistake, because that would be only valid for immutable data structures. And I suppose with immutable data structures you get only part of the advantages of shared memory, right? What good is a parallel RAM if it doesn&#39;t support concurrent writes? <br>
<br>So, I think, no matter what kind of abstract concurrency primitives you provide, you&#39;d still need proper shared memory + threads for the low-level programmer. Or as I said, you can also get speedup using MPI, but usually that&#39;s not the best speedup you are going to get because a) you can&#39;t avoid copying huge messages across processes b) mpi implementation may have too much penalty for finer-grain code, i.e. latency will become significant. I think MPI or these high-level concurrent processes would be good on shared memory if the problem is embarrasingly parallel. But as we all know only a small minority of problems turn out to be that easy to solve in parallel!<br>
<br>At any rate, I&#39;m sure we&#39;ll have it one day, I&#39;m keeping my fingers crossed :)<br><br>Best,<br><br>-- <br>Eray Ozkural, PhD candidate.  Comp. Sci. Dept., Bilkent University, Ankara<br><a href="http://groups.yahoo.com/group/ai-philosophy">http://groups.yahoo.com/group/ai-philosophy</a><br>
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