Calling octave functions from oct-files

[Muthiah Annamalai]

Evan wrote:
> On Jan 13, 2008 2:30 PM, John W. Eaton <jwe at bevo.che.wisc.edu> 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?
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>
>   

I think numbers maybe wrong here. You are adding the DLD-loading time
as well. So you better do something like autoload('fun1','fun1.oct') before
running your profiles.
-Muthu