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Re: parcellfun Uses Only One Core


From: c.
Subject: Re: parcellfun Uses Only One Core
Date: Fri, 27 Dec 2013 06:16:07 +0100

Hi,

Please do not top post  (put your reply at the bottom of the mail, not at the 
top)
and keep the list in CC.

>>> On 26 Dec 2013, at 22:02, Henry Shu <address@hidden> wrote:
>>> Indeed, if I open 4 Octave sessions and have each run the following, all 
>>> the cores in my i7-4770K desktop would be utilized.
>>> 
>> On Dec 26, 2013 2:07 PM, "c." <address@hidden> wrote:
>> Actually this is not very much different from what parcellfun actually does: 
>> it opens 4 Octave processes, pipes chunks of data to them and then executes 
>> the function on them.
>> If you launch "parcellfun (4, ...)" and then type "top" in a terminal window 
>> do you see 4 instances of Octave running?
>> 
>> c.
> 
> On 27 Dec 2013, at 00:59, Henry Shu <address@hidden> wrote:
> With "top" I do see 4 instances running. However, all 4 of these instances 
> are using one logical core: each of the 4 instances has 25% cpu usage. 
> Ubuntu's system monitor also confirms that the other 7 logical cores are idle.
> 
> The expected behavior is for each instance to utilize each logical core 
> fully, so that each Octave instance would show 100% cpu usage. This is indeed 
> the case on my i7 laptop. Maybe somehow Octave now thinks that my desktop 
> only has one core?

"parcellfun" does not guess anything about your hardware, 
it just spawns new istances via "fork" and leaves the rest to your OS,
so it does not matter what Octave "thinks".
 
If your cpus are not being used equally you will have to check 
the settings of your OS to find out why.

c.

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