[bug #68090] Performance improvements to classdef load-save in MAT-files

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URL:
  <https://savannah.gnu.org/bugs/?68090>

                 Summary: Performance improvements to classdef load-save in
MAT-files
                   Group: GNU Octave
               Submitter: foreverallama
               Submitted: Wed 25 Feb 2026 04:29:04 PM UTC
                Category: Classdef
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name:
        Originator Email:
             Open/Closed: Open
         Discussion Lock: Unlocked
                 Release: dev
        Operating System: Any
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Wed 25 Feb 2026 04:29:04 PM UTC By: foreverallama <foreverallama>
This patch contains some small performance improvements to load-save of
classdef objects in MAT-file subsystem data. Changes as follows:
* New exception class "subsystem_exception" in ls-mat-subsys.h
* Throw/Handle exceptions for unsupported version and property type
* Add test for exception handling (with binary modified MAT-files)
Note: Is it a good idea to add a catch-all and raise an error? Could prevent
Octave from crashing, although surprisingly MATLAB doesn't seem to handle
it/crashes as well.

Performance Optimizations:
* Prevent subsystem data from loading twice (for some reason,
"read_mat5_binary_file_header" runs twice)
* Wrap uint8 subsystem data around a custom memory buffer to prevent copying
for processing
* Small performance improvements to loading property values, class and
property names

I believe subsystem load-save is reasonably optimised. The main bottleneck is
actually in loading integer types, for which I will open a separate bug






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File Attachments:

Name: optimize_subsystem.patch       Size: 14KiB

<https://file.savannah.gnu.org/file/optimize_subsystem.patch?file_id=58278>

Name: unsupported-version.mat        Size: 1.4KiB
    <https://file.savannah.gnu.org/file/unsupported-version.mat?file_id=58279>

Name: unsupported-prop-type.mat      Size: 1.4KiB

<https://file.savannah.gnu.org/file/unsupported-prop-type.mat?file_id=58280>



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