Use Octave's interpreter in my C++ program...

[Molamini]

Hello,
I would like to use Octave in a C++ multithreaded application.  Is there
something like this (see code below) in Octave so I can get an instance of
Octave and use it throughout the life of my OctaveUser object?  I'll even
take something close to this. :)

class OctaveUser
{
   private:
     OctaveInstance *p_oi;
   public:
    OctaveUser()
    {
        oi = OctaveFactory::createInstance();
    }
    void cppMethod()
    {
        Matrix m(2,2);
        m(0,0)=1; m(0,1)=2;
        m(1,0)=3; m(1,1)=4;
        oi.feval("invert", m);

        // call 'testFromCpp.m' file.
        octave_value_list result = feval ("testFromCpp", octave_value (m),
1 );
        ...//do something with the value in C++
    }

    ~OctaveUser()
    {
        delete _oi;
    }
};

Thanks!
Molamini

[John Swensen]

On May 22, 2008, at 5:26 PM, jmoliere@... wrote:

> Hello,
> I would like to use Octave in a C++ multithreaded application.  Is  
> there
> something like this (see code below) in Octave so I can get an  
> instance of
> Octave and use it throughout the life of my OctaveUser object?  I'll  
> even
> take something close to this. :)
>
> class OctaveUser
> {
>   private:
>     OctaveInstance *p_oi;
>   public:
>    OctaveUser()
>    {
>        oi = OctaveFactory::createInstance();
>    }
>    void cppMethod()
>    {
>        Matrix m(2,2);
>        m(0,0)=1; m(0,1)=2;
>        m(1,0)=3; m(1,1)=4;
>        oi.feval("invert", m);
>
>        // call 'testFromCpp.m' file.
>        octave_value_list result = feval ("testFromCpp", octave_value  
> (m),
> 1 );
>        ...//do something with the value in C++
>    }
>
>    ~OctaveUser()
>    {
>        delete _oi;
>    }
> };
>
> Thanks!
> Molamini
>

Included is a bit of pseudo-code that I wrote to an Octave user  
offline from the mailing list that I think would be the "meat" of such  
a class.  This listing, however, is unique to the Octave sources since  
the change to the sumbol_table in a singleton class as described in  
the explanation.  Hope this helps.  If I had more time, I would  
implement it, but would be willing to give help if you want to muck  
around with this.  However, take note of David Bateman's warning about  
thread-safety.  I suppose if you ensure you only call into octave one  
command at a time, then Bob is your uncle.

<begin previous email>
I think the better way of doing this would be to create a symbol_record
and insert it into the symbol_table singleton class.  Then you could use
the octave_call() function one the variable that you just pushed into
the octave environment.  Then, pull the resulting variable out of the
symbol_table and pull the data from the contained octave_value().  Below
is a bit of pseudo-code that seems like it should work.  I hope this
helps.  If this does end up working, would you be willing to write and
email to the mailing list with how you did it.  I think this would be
useful for others to know about, since I haven't seen someone do this
before.  Also, not that the pseudocode I give below is based on the most
recent octave from the source code repository.  Between 3.0.x and what
is in the repository, I think there was a major change in the symbol
table.  Before, it was just a global variable.  Now it is a singleton
class.  The changes between 3.0.1 and the current repository tip are
significant, but the basic idea should be the same.

unsigned int imageArry[1024*768];
unsigned int resultImageArry[1024*768];

captureImage (imageArry);

Matrix octImageArry(768,1024); // Note, octave indexes as row x col
// COPY YOUR IMAGE DATA INTO THIS MATRIX
for (int row = 0; row < size; ++row)
{
  for (int column = 0; column < size; ++column)
  {
    // I'm not sure how your image is indexed in memory, so you should  
populate the matrix properly
    octImageArry (row, column) = imageArry[col][row];
  }
}

// Wrap your octave_value Matrix up in a symbol_record object
symbol_table::symbol_record symrec_imageArry ("imageArry",  
octImageArry);

// Insert your symbol_record into the symbol_table
symbol_table::insert_symbol_record (symrec_imageArry);

// Call your routine to process the image
octave_call("resultImageArry=processImageData(imageArry);");

// Pull the newly created symbol record called "resultImageArry" out  
of the symbol_table
symbol_record symrec_resultImageArry =  
symbol_table::find_symbol("resultImageArry");

// Pull the octave_value out of the result symbol_record
octave_value octResultImageArry = symrec_resultImageArry.varval();

// COPY THE DATA OUT OF THIS OCTAVE_VALUE AND BACK INTO YOUR C/C++ ARRAY
<end previous email>

[bernddude]

Hello Molamini, i am looking for exactly the same solution if you do happen to find on,
would you mind to let me know

thanks bernd

Molamini wrote:

Hello,
I would like to use Octave in a C++ multithreaded application.  Is there
something like this (see code below) in Octave so I can get an instance of
Octave and use it throughout the life of my OctaveUser object?  I'll even
take something close to this. :)

class OctaveUser
{
   private:
     OctaveInstance *p_oi;
   public:
    OctaveUser()
    {
        oi = OctaveFactory::createInstance();
    }
    void cppMethod()
    {
        Matrix m(2,2);
        m(0,0)=1; m(0,1)=2;
        m(1,0)=3; m(1,1)=4;
        oi.feval("invert", m);

        // call 'testFromCpp.m' file.
        octave_value_list result = feval ("testFromCpp", octave_value (m),
1 );
        ...//do something with the value in C++
    }

    ~OctaveUser()
    {
        delete _oi;
    }
};

Thanks!
Molamini

[John Swensen]

On May 22, 2008, at 5:41 PM, John Swensen wrote:

>
> On May 22, 2008, at 5:26 PM, jmoliere@... wrote:
>
>> Hello,
>> I would like to use Octave in a C++ multithreaded application.  Is  
>> there
>> something like this (see code below) in Octave so I can get an  
>> instance of
>> Octave and use it throughout the life of my OctaveUser object?  
>> I'll even
>> take something close to this. :)
>>
>> class OctaveUser
>> {
>>  private:
>>    OctaveInstance *p_oi;
>>  public:
>>   OctaveUser()
>>   {
>>       oi = OctaveFactory::createInstance();
>>   }
>>   void cppMethod()
>>   {
>>       Matrix m(2,2);
>>       m(0,0)=1; m(0,1)=2;
>>       m(1,0)=3; m(1,1)=4;
>>       oi.feval("invert", m);
>>
>>       // call 'testFromCpp.m' file.
>>       octave_value_list result = feval ("testFromCpp", octave_value  
>> (m),
>> 1 );
>>       ...//do something with the value in C++
>>   }
>>
>>   ~OctaveUser()
>>   {
>>       delete _oi;
>>   }
>> };
>>
>> Thanks!
>> Molamini
>>

So I went ahead and converted a class I had written for the Matlab  

Engine into a similar class for Octave.  It is based on the pseudo-
code I sent in my last email.  I have attached a tgz file with the  
simple class and a test program.  This is based on the concept of  
starting up octave_main() in embedded mode, pushing and pulling  
variables from the symbol table, and calling eval string to perform  
actions.  Would the maintainers ever be interested in incorporating a  
more full-fledged version into Octave.  As with the MEX interface, we  
could make the functions act like the Matlab Engine counterparts.

John Swensen

[David Bateman]

John Swensen wrote:
>
> So I went ahead and converted a class I had written for the Matlab
> Engine into a similar class for Octave.  It is based on the
> pseudo-code I sent in my last email.  I have attached a tgz file with
> the simple class and a test program.  This is based on the concept of
> starting up octave_main() in embedded mode, pushing and pulling
> variables from the symbol table, and calling eval string to perform
> actions.  Would the maintainers ever be interested in incorporating a
> more full-fledged version into Octave.  
Hey, who's a maintainer? It all depends as far as I see on your
motivation to maintain the code.. However, the general line drawn on
what goings into Octave or octave-forge is based on whether the
equivalent functionality is a core matlab functionality. There are
exceptions of course...
> As with the MEX interface, we could make the functions act like the
> Matlab Engine counterparts.
Is the Matlab Engine your code or is it something more generic? If its
generic then it makes sense to try and have a class that performs with
Octave with the same API such that application written for one interface
can use the other.

D.


--
David Bateman                                David.Bateman@...
Motorola Labs - Paris                        [phone] (Ph)
Parc Les Algorithmes, Commune de St Aubin    [phone] (Mob)
91193 Gif-Sur-Yvette FRANCE                  [phone] (Fax)

The information contained in this communication has been classified as:

[x] General Business Information
[ ] Motorola Internal Use Only
[ ] Motorola Confidential Proprietary

[John Swensen]

On May 23, 2008, at 10:44 AM, David Bateman wrote:

>
>> As with the MEX interface, we could make the functions act like the
>> Matlab Engine counterparts.
> Is the Matlab Engine your code or is it something more generic? If its
> generic then it makes sense to try and have a class that performs with
> Octave with the same API such that application written for one  
> interface
> can use the other.
>
> D.
>

So the Matlab Engine is a core Matlab functionality.  It is *not* a  
class, but a collection of functions.  You can see the API at
http://www.mathworks.com/access/helpdesk/help/techdoc/index.html?/access/helpdesk/help/techdoc/matlab_external/f29148.html&http://www.google.com/search 
?client=safari&rls=en-us&q=Matlab+Engine&ie=UTF-8&oe=UTF-8.

Since people have already implemented a bunch/all of the mxArray  
functions, it might make sense to add these engine functions.  As you  
can see in the class I wrote,  implementing the functions listed in  
the URL I included will be trivial; simply converting my class into a  
non-class with the same functionality and the function names that  
match the Matlab Engine function.  However, if we do so, is there a  
way to ensure that they are only used when it is compiled with the  
mkoctfile --link-stand-alone option?

John Swensen

[David Bateman]

John Swensen wrote:

>
> On May 23, 2008, at 10:44 AM, David Bateman wrote:
>>
>>> As with the MEX interface, we could make the functions act like the
>>> Matlab Engine counterparts.
>> Is the Matlab Engine your code or is it something more generic? If its
>> generic then it makes sense to try and have a class that performs with
>> Octave with the same API such that application written for one interface
>> can use the other.
>>
>> D.
>>
>
> So the Matlab Engine is a core Matlab functionality.  It is *not* a
> class, but a collection of functions.  You can see the API at
> http://www.mathworks.com/access/helpdesk/help/techdoc/index.html?/access/helpdesk/help/techdoc/matlab_external/f29148.html&http://www.google.com/search?client=safari&rls=en-us&q=Matlab+Engine&ie=UTF-8&oe=UTF-8.
>
>
> Since people have already implemented a bunch/all of the mxArray
> functions, it might make sense to add these engine functions.  As you
> can see in the class I wrote,  implementing the functions listed in
> the URL I included will be trivial; simply converting my class into a
> non-class with the same functionality and the function names that
> match the Matlab Engine function.  However, if we do so, is there a
> way to ensure that they are only used when it is compiled with the
> mkoctfile --link-stand-alone option?
>
> John Swensen
>
>

Then it makes sense to have these in Octave itself.. However looking at
the engOpen command from the above link it appears that in fact Matlab
uses something like a fork/exec to create an entirely new process with
the Matlab instance running in it, rather than use a thread in the
current process, thus avoiding all the issues of thread safety. So what
you are proposing in fact goes beyond what is implemented in the Matlab
engine..

D.



--
David Bateman                                David.Bateman@...
Motorola Labs - Paris                        [phone] (Ph)
Parc Les Algorithmes, Commune de St Aubin    [phone] (Mob)
91193 Gif-Sur-Yvette FRANCE                  [phone] (Fax)

The information contained in this communication has been classified as:

[x] General Business Information
[ ] Motorola Internal Use Only
[ ] Motorola Confidential Proprietary

[Mirek23]

Dear John Swensen,

>So I went ahead and converted a class I had written for the Matlab  
>Engine into a similar class for Octave.  It is based on the pseudo-
>code I sent in my last email.  I have attached a tgz file with the  
>simple class and a test program.  This is based on the concept of  
>starting up octave_main() in embedded mode, pushing and pulling  
>variables from the symbol table, and calling eval string to perform  
>actions.  Would the maintainers ever be interested in incorporating a  
>more full-fledged version into Octave.  As with the MEX interface, we  
>could make the functions act like the Matlab Engine counterparts.

I have tried out your idea and it works very well for me. Your new approach looks much better than the previous embedded one which referred to matrices conversion from ASCII to the internal octave representation and back to ASCII.

Thank you very much for this great idea.

Best Regards

Miroslaw Dach