July 18, 2010
On 07/16/2010 04:48 AM, Don wrote:
> Georg Wrede wrote:
>> On 07/14/2010 08:55 PM, dsimcha wrote:
>>> It would be nice to not have to manually specify such a
>>> parameter on every run, but not nice enough to be
>>> worth introducing a dependency.
>> I can't imagine how this would not be a required part of the core
>> library.
>> For a language that claims to be thread savvy, knowing the number of
>> cpus and the number of cores, is simply obligatory homework.
>> An extra point: the code that identifies them, should not ever assume
>> that all cores are identical. Nor that they have identical access to
>> machine resources.
>> The day that someone invents the 'unequal cores paradigm', where cores
>> of dissimilar power are included in the same computer, should not
>> expose us with our pants down.
> It really depends on what the purpose is. If you want to determine the
> precise core topology, the available information is heavily
> OS-dependent. Note that there's potentially a large difference between
> the number of cores in the machine, versus the number of cores which the
> OS makes available to your app. Generally the second number is the one
> which matters.

True. What my app needs D to tell it, is to enumerate and specify the processors (and of course any other variable resources) available to this particular instance of running program.

>> (A case in point, at bootup, the Linux core already enumerates and
>> evaluates each found core individually.)
> Of course it does. It's trivial when you're an OS and have unrestricted
> access to the machine. An app is severely limited to what it can get
> from the OS.
> Currently core.cpuid doesn't make any OS calls at all.
> I think std.cpuid should be replaced with a new module std.sysinfo,
> which determines more features (such as available RAM).


Runtime initialization code should find out the resources available to the current app instance. Anything else can (or should) be available from /proc/... (or, whatever equivalents Bill G or Steve J have decided), and the app is free to roam around in that directory tree.
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