bugGNU Octave - Bugs: bug #60251, [octave forge] (parallel) strange...

 
 

bug #60251: [octave forge] (parallel) strange execution times

Submitter:  Muhali <muhali>
Submitted:  Wed 17 Mar 2021 04:51:55 PM UTC
   
 
Category:  Octave Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  None
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * 6.1.0 Operating System:  * GNU/Linux
Fixed Release:  None Planned Release:  None
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Wed 17 Mar 2021 06:20:18 PM UTC, comment #1: 

Starting with 4.0.0, parallel uses freshly started Octave sessions as parallel workers. These are started by the first call to parcellfun. (More are started if 'parcellfun's first argument is larger than in any call before.) This makes the first call take longer time. 9 seconds for 'nproc' starts of 'octave-cli' seems long, though...

That the second call takes longer than in version 3.1.3 may be expected (although a comparison with different Octave compilations is only rough), since the communication between the master and slave sessions in versions starting with 4.0.0 constitutes some overhead.

 Olaf Till <i7tiol>
Group Member
Wed 17 Mar 2021 04:51:55 PM UTC, original submission:  

As the code below shows, the newer parallel package (4.0.0, with octave-6) has some strange execution time behavior.


pkg load parallel

n = 3000 ;
I = num2cell(1:n) ;

tic ;
C = parcellfun(nproc, @(x) 1:n == x, I, "UniformOutput", false, "VerboseLevel", 0) ;
toc
tic ;
C = parcellfun(nproc, @(x) 1:n == x, I, "UniformOutput", false, "VerboseLevel", 0) ;
toc


The result is

Elapsed time is 9.65733 seconds.
Elapsed time is 0.534994 seconds.

When doing the same with the old version (3.1.3, with octave-5) one gets

Elapsed time is 0.339917 seconds.
Elapsed time is 0.325187 seconds.

Muhali <muhali>

 

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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2021-04-28 siko1056 Summary[octave-forge] (parallel) strange execution times [octave forge] (parallel) strange execution times
    2021-03-21 rik5 Carbon-CopyRemoved 72865 -
    2021-03-21 rik5 CategoryNone Octave Package

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