[Vm-dev] Re: Efficient thread-local shared variables

Klaus D. Witzel klaus.witzel at cobss.com
Tue Oct 24 05:33:00 UTC 2006

Hi Andreas,

on Tue, 24 Oct 2006 06:46:26 +0200, you wrote:

> Folks -
> For a variety of reasons I am in dire need of the ability to vector  
> shared variables (globals, class vars and pool vars) through an extra  
> indirection vector per process (really per island but binding per  
> process seems to be simpler for now). Since I need this for *each and  
> every shared variable* it needs to be *very* efficient.
> The question is: What is the most efficient way to implement such a  
> scheme?

The fastest indirect access is through literal variables (limited only by  
the # of literals allowed per method).

Since you are willing to spend a #symbol per variable, formally declare a  
"descriptor" to be a class var (or use a pool). Take #PerProcessThing as  
as example; initialize PerProcessThing to a subinstance of Association  
which holds a fast and fixed Array index.

Then all you need in the scope of activeProcess is a shared Array which is  
indexed by the above machinery. Example use:

	PerProcessThing localSharedValue
	PerProcessThing localSharedValue: somethingElse

Not counting "Processor activeProcess scope", the above is the fastest  
double-indirect access that I can think of.


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