Re: Calling octave functions from oct-files

[Evan]

On Jan 13, 2008 2:30 PM, John W. Eaton <address@hidden> wrote:
>
> On 13-Jan-2008, Evan wrote:
>
> | I am converting some part of my program from octave scripts to
> | oct-files in order to improve performance. I find that I have to call
> | octave functions in a for loop. And if I use "feval" to do this, it
> | consumes a lot of time. The result is that the oct-file is even slower
> | than the octave script. So I wonder if there is an another way to call
> | octave functions. For example, can I get the pointer to the function,
> | then just use (*p)(args) to call the function?
>
> No.
>
> Maybe you could give a complete (but short) example that shows what
> you are trying to do?  I don't think feval from a .oct file should be
> slower than running an interpreted script.
>

What I am trying to do is something like

for (i = 0; i < n; i++)
  {
    quad_args(2) = xf(i);
    feval ("quad", quad_args, 4);
  }

It turns out to be slower than the corresponding script


I also tried the following examples

// fun1.cc
#include <octave/oct.h>
#include <octave/parse.h>

DEFUN_DLD (fun1, args, , "fun1")
{
  return feval("sin", octave_value (3), 1);
}
//end of fun1.cc

// fun2.cc
#include <octave/oct.h>
#include <octave/parse.h>

DEFUN_DLD (fun2, args, , "fun2")
{
  int state;
  return eval_string ("sin(3)", true, state, 1);
}
// end of fun2.cc

I compared the runing time of fun1, fun2 and sin(3) in octave by
tic; fun1; toc
tic; fun2; toc
tic; sin(3); toc
I find that fun1 and fun2 are hundreds of times slower than sin(3).
(I have taken into account the time consumed by "tic;toc")

any ideas?