[M3devel] defaulting to parallel backend?

[Jay K]

 There is no good easy answer here. 

 You really want everything on the computer to use all of the  available resources, to service whatever the human wants done  as fast as possible, while remaining responsive e.g. to  requests to cancel or requests to increase the work load. 

 This is largely the job of the kernel, but it is an impossible job.  
 To some extent we are obligated to over subscribe, in order to provide the kernel more information. But, again, it is an impossible job.
 Besides it probably being NP complete to complete the submitted work as soon as possible, we also don't know the user's priorities.
 I could propose "pb 1" to mean run single threaded, putting the burden on you to give. But that is a little rude.
 Note that historically you didn't have as much flexibility here -- single core systems.

 Anyway, how about the default be half?  Or 1 if <= 3 cores available?  I seem to have 4 cores, so this will help me. 

 I understand this is still not great, e.g. if you have 10 high priority single processors jobs, and one low priority Modula-3 build, Modula-3 will by default use more than you wish.
  And yes, I understand disk are another resource. And network -- disk can be on network. You want to operate at the "edge of resource exhaustion" in general.

 - Jay



> Date: Tue, 5 Jul 2016 18:36:45 +0200
> From: lemming at henning-thielemann.de
> To: rodney.m.bates at acm.org
> Subject: Re: [M3devel] defaulting to parallel backend?
> CC: m3devel at elegosoft.com
> 
> 
> On Mon, 4 Jul 2016, Rodney M. Bates wrote:
> 
> > I prefer to use one fewer than the number of processors, so I can
> > web browse, read email, review code, etc. while waiting for a
> > compile.  The compiler can saturate them all, making any other
> > stuff very slow.
> 
> Slowdown can happen even earlier if the compilation is bound by disk 
> access time.
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