performance hit with functions of vectors

[augustm]

Hello,

I am using a version of octave-3.0.0, compiled on a 64-bit linux machine using gcc.
(I am NOT using the experimental enable-64 options)

I am troubled by the variability of function evaluations speeds applied to vectors;
I have a vector of variables of length 30,000.

octave:1> whos zz

*** local user variables:

  Prot Name        Size                     Bytes  Class
  ==== ====        ====                     =====  ===== 
   rwd zz      30000x1                     360008  double


Their range is quite reasonable- so there is no question of under/overflow
octave:2> min(zz)
ans = Compressed Column Sparse (rows = 1, cols = 1, nnz = 1)
  (1, 1) ->  0.15938
octave:3> max(zz)
ans = Compressed Column Sparse (rows = 1, cols = 1, nnz = 1)
  (1, 1) ->  170.70


I perform a simple function evaluation- it's fast

octave:4>  tic; j=sin(zz); toc
Elapsed time is 0.0016 seconds.


However now the problem!

*********************************
octave:5> tic; j=cos(zz); toc
Elapsed time is 0.59 seconds.
**********************************

certain functions are 400 times slower than others.


Thus

tic; j=log(zz); toc
Elapsed time is 0.59 seconds.


but this is much better

tic; j=tan(zz); toc
Elapsed time is 0.002 seconds.


I am a bit lost how to go further. I can send full compilation details if needed.
Most extras were compiled in- SuiteSparse etc.

TM


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