[Octave-bug-tracker] [bug #64840] VM __vm_enable__ seems to have not negligible overhead losses (~5%) in certain situations

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?64840>

                 Summary: VM __vm_enable__ seems to have not negligible
overhead losses (~5%) in certain situations 
                   Group: GNU Octave
               Submitter: None
               Submitted: Mon 30 Oct 2023 03:31:42 AM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: dev
         Discussion Lock: Any
        Operating System: GNU/Linux
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 30 Oct 2023 03:31:42 AM UTC By: Anonymous
The performance of code executed using the VM and using vm_enabled flag = true
seems to cause (in certain situations) a non negligible overhead:

In the example below the VM is faster than the hierarchical interpreter, but
~5% slower compared to code which uses the VM (only) for the pre-compiled key
function and sets vm_enabled = false.

Whilst some overhead is expected and unavoidable, there seem to be room for
improvement with the noted 5% performance drop.
 


__vm_enable__(0);
clear test2; clear quadv;
tic;
for i=1:10000
  y = test2(0, 2*pi);
endfor
toc;


__vm_enable__(1);
clear test2; clear quadv;
tic;
for i=1:10000
  y = test2(0, 2*pi);
endfor
toc;

__vm_enable__(0);
clear test2; clear quadv;
__vm_compile__("quadv"); 
tic;
for i=1:10000
  y = test2(0, 2*pi);
endfor
toc;



function ret = test2(a,b);
  ret = quadv(@(x) sin(x), a, b);
endfunction


results in

Elapsed time is 5.68666 seconds.
Elapsed time is 3.71263 seconds.
Elapsed time is 3.50177 seconds.
>> 1-3.50177/3.71263
ans = 0.056795



Note: Interesting is that when in addition to quadv, test2 is also
pre-compiled and vm_enabled = false, the overall performance becomes (a little
~2%) slower compared to vm_enabled flag = true. 

   







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