[Octave-bug-tracker] [bug #63939] strange performance of sparse matrix operations

[Andreas Stahel]

URL:
  <https://savannah.gnu.org/bugs/?63939>

                 Summary: strange performance of sparse matrix operations
                   Group: GNU Octave
               Submitter: andreasstahel
               Submitted: Fri 17 Mar 2023 03:54:25 PM UTC
                Category: Performance
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: Andreas Stahel
        Originator Email: 
             Open/Closed: Open
                 Release: 8.1.0
         Discussion Lock: Any
        Operating System: GNU/Linux
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


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Date: Fri 17 Mar 2023 03:54:25 PM UTC By: Andreas Stahel <andreasstahel>
On a tight loop with sparse matrices 
(one matrix*vector, one system solve by \, both with the same matrix) 
the results depends in a stange way on value OMP_NUM_THREADS=32
Octave with GUI started.

export OMP_NUM_THREADS=32
leads to 25 seconds of wall time

export OMP_NUM_THREADS=16
leads to 5 seconds of wall time

CPU: AMD Ryzen 9 3950X 16-Core Processor, 
hyperthreading enabled, i.e. the OS sees 32 cores, 64GB RAM
Xubuntu 22.04

The development version and 8.1.0 lead to the same results






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File Attachments:


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Date: Fri 17 Mar 2023 03:54:25 PM UTC  Name: TestSparse.m  Size: 485B   By:
andreasstahel

<http://savannah.gnu.org/bugs/download.php?file_id=54507>

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  <https://savannah.gnu.org/bugs/?63939>

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