[Octave-bug-tracker] [bug #61912] Slow performance of complex()

[Rik]

Follow-up Comment #10, bug #61912 (project octave):

Responses to comments #7 and #8

@jwe: I agree, no need to use reinterpret_cast.  I was looking for any
technique that might show an improvement.  I guess I'll prepare a changeset
that adds in a comment about why the "new" operator is being used and make the
other small changes to not initialize the array and to use xelem.

@hg200: I noticed the same thing, specifically that function calling seems to
be quite slow.  As a test, I replaced the entire Fcomplex function in data.cc
with


return octave_value (1.0);


I then used this test code


N = 1e5;

if (! exist ("val"))
  val = rand (1e2, 1);
endif

tic;
for i = 1 : N
#  z = complex (val, val); 
  z = val + 1i*val; 
endfor
bm = toc


Timings were

complex(): 0.32
multiplication: 0.23

This is remarkable given that in the multiplication case actual work was being
done and it still beat the no-op version of complex().  That observation
probably deserves its own bug report. 

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