Thread Subject:

C++ implementation of interp2 function

Hi,

I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.

I want to replace this interp2 Matlab function with a C++ version to make my code faster.

What is the easiest way to do so?
Should i compile the "interp2" to cpp and than call it's DLL in my M file (i don't know how to do the compiling) ? or maybe there is a prepared C++ version of this Matlab function that i can use?

Thanks a lot,
Yossi

On 7 Des, 23:36, "Yossi " <yo...@tx.technion.ac.il> wrote:
> Hi,
>
> I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.
>
> I want to replace this interp2 Matlab function with a C++ version to make my code faster.
>
> What is the easiest way to do so?

If you want 'easy' stick with matlab.

While C++ programs might be significantly faster than
the matlab counterparts, developing them does not come
for free. Programming C++ requires quite a bit more
knowledge and insight into what a computer is and how
it works, than matlab does.

Rune

Rune Allnor <allnor@tele.ntnu.no> wrote in message <e965c3b5-7d02-4795-9bc6-502be0f7e8ee@r40g2000yqn.googlegroups.com>...
> On 7 Des, 23:36, "Yossi " <yo...@tx.technion.ac.il> wrote:
> > Hi,
> >
> > I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.
> >
> > I want to replace this interp2 Matlab function with a C++ version to make my code faster.
> >
> > What is the easiest way to do so?
>
> If you want 'easy' stick with matlab.
>
> While C++ programs might be significantly faster than
> the matlab counterparts, developing them does not come
> for free. Programming C++ requires quite a bit more
> knowledge and insight into what a computer is and how
> it works, than matlab does.
>
> Rune


I know C++ programming but i don't want to Reinventing the wheel and write spline2 in cpp by myself. I want to use the Matlab compiler to do so or maybe this translation to cpp is already made and i just have to call it's dll from my M file..

I need this interp2 dll realy badly..
Thanks,
Yossi

"Yossi " wrote:
> Hi,
>
> I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.
>
> I want to replace this interp2 Matlab function with a C++ version to make my code faster.
>
> What is the easiest way to do so?
> Should i compile the "interp2" to cpp and than call it's DLL in my M file (i don't know how to do the compiling) ? or maybe there is a prepared C++ version of this Matlab function that i can use?
>
> Thanks a lot,
> Yossi

Hi

If your input data is regularly spaced (e.g. an image) then there is a mex version of interp2 (called vgg_interp2) in the toolbox available here:
http://www.robots.ox.ac.uk/~ojw/files/imrender_v2.4.zip
It's especially useful for sampling multi-channel images. It also runs faster if your compiler supports OpenMP (and you have this option enabled).

Oliver

On 8 Des, 07:40, "Yossi " <yo...@tx.technion.ac.il> wrote:
> Rune Allnor <all...@tele.ntnu.no> wrote in message <e965c3b5-7d02-4795-9bc6-502be0f7e...@r40g2000yqn.googlegroups.com>...
> > On 7 Des, 23:36, "Yossi " <yo...@tx.technion.ac.il> wrote:
> > > Hi,
>
> > > I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.
>
> > > I want to replace this interp2 Matlab function with a C++ version to make my code faster.
>
> > > What is the easiest way to do so?
>
> > If you want 'easy' stick with matlab.
>
> > While C++ programs might be significantly faster than
> > the matlab counterparts, developing them does not come
> > for free. Programming C++ requires quite a bit more
> > knowledge and insight into what a computer is and how
> > it works, than matlab does.
>
> > Rune
>
> I know C++ programming

Not well enough for what you attempt to do:

1) Somebody who knows C++ would not ask for 'easy' methods
2) Somebody who knows C++ would not ask in a matlab forum

Rune

Rune Allnor <allnor@tele.ntnu.no> wrote in message <0f6f6d4d-5a8a-4703-bc88-b34c242e9a5f@j24g2000yqa.googlegroups.com>...
> On 8 Des, 07:40, "Yossi " <yo...@tx.technion.ac.il> wrote:
> > Rune Allnor <all...@tele.ntnu.no> wrote in message <e965c3b5-7d02-4795-9bc6-502be0f7e...@r40g2000yqn.googlegroups.com>...
> > > On 7 Des, 23:36, "Yossi " <yo...@tx.technion.ac.il> wrote:
> > > > Hi,
> >
> > > > I'm using a Matlab script that calls the "interp2" function several times (in loops), this makes the run-time extremely longer.
> >
> > > > I want to replace this interp2 Matlab function with a C++ version to make my code faster.
> >
> > > > What is the easiest way to do so?
> >
> > > If you want 'easy' stick with matlab.
> >
> > > While C++ programs might be significantly faster than
> > > the matlab counterparts, developing them does not come
> > > for free. Programming C++ requires quite a bit more
> > > knowledge and insight into what a computer is and how
> > > it works, than matlab does.
> >
> > > Rune
> >
> > I know C++ programming
>
> Not well enough for what you attempt to do:
>
> 1) Somebody who knows C++ would not ask for 'easy' methods
> 2) Somebody who knows C++ would not ask in a matlab forum
>
> Rune

I'm just asking for easy methos to translate interp2.m to cpp file, i just don't want to waste my time on "manual" translation to c++ (i think Matlab compiler can do it). I'm asking in this forum because the issue is a Matlab function called "interp2" and maybe the Matlab compiler could do the job here...

Thanks,
Yossi

This is an excellent question actually. If you haven't found the answer yet, this should help you, I'd think:
http://www.mathworks.com/access/helpdesk/help/toolbox/compiler/f7-996707.html
Otherwise the MATLAB Compiler User's Guide...

This is an excellent question actually. If you haven't found the answer yet, this should help you, I'd think:
http://www.mathworks.com/access/helpdesk/help/toolbox/compiler/f7-996707.html
Otherwise the MATLAB Compiler User's Guide...

"Yossi " wrote:
> I'm just asking for easy methos to translate interp2.m to cpp file.

Yossi, did you see my earlier comment? The function I mention might do what you're after (the functionality is mostly the same as interp2, with some differences).

Oliver

"Yossi " <yosst@tx.technion.ac.il> wrote in message <hflajm$q8s$1@fred.mathworks.com>...

> I'm just asking for easy methos to translate interp2.m to cpp file, i just don't want to waste my time on "manual" translation to c++ (i think Matlab compiler can do it). I'm asking in this forum because the issue is a Matlab function called "interp2" and maybe the Matlab compiler could do the job here...
>

I would be surprised if the matlab compiler would
actually make interp2 run significantly faster.

A HAND coded version might give you a nice speed
gain, but just brute force compilation often does not
gain much.

John

"John D'Errico" <woodchips@rochester.rr.com> wrote in message <hfo0pp$clg$1@fred.mathworks.com>...
> "Yossi " <yosst@tx.technion.ac.il> wrote in message <hflajm$q8s$1@fred.mathworks.com>...
>
> > I'm just asking for easy methos to translate interp2.m to cpp file, i just don't want to waste my time on "manual" translation to c++ (i think Matlab compiler can do it). I'm asking in this forum because the issue is a Matlab function called "interp2" and maybe the Matlab compiler could do the job here...
> >
>
> I would be surprised if the matlab compiler would
> actually make interp2 run significantly faster.
>
> A HAND coded version might give you a nice speed
> gain, but just brute force compilation often does not
> gain much.
>
> John

Thanks John, maybe its not the right place to ask but if you know where i can find in the web a reliable DLL that wraps a C++ implementation of 2D interpolation, i'll be happy to hear

Thanks,
Yossi

"Yossi " <yosst@tx.technion.ac.il> wrote in message <hfo95u$23j$1@fred.mathworks.com>...
> "John D'Errico" <woodchips@rochester.rr.com> wrote in message <hfo0pp$clg$1@fred.mathworks.com>...
> > "Yossi " <yosst@tx.technion.ac.il> wrote in message <hflajm$q8s$1@fred.mathworks.com>...
> >
> > > I'm just asking for easy methos to translate interp2.m to cpp file, i just don't want to waste my time on "manual" translation to c++ (i think Matlab compiler can do it). I'm asking in this forum because the issue is a Matlab function called "interp2" and maybe the Matlab compiler could do the job here...
> > >
> >
> > I would be surprised if the matlab compiler would
> > actually make interp2 run significantly faster.
> >
> > A HAND coded version might give you a nice speed
> > gain, but just brute force compilation often does not
> > gain much.
> >
> > John
>
> Thanks John, maybe its not the right place to ask but if you know where i can find in the web a reliable DLL that wraps a C++ implementation of 2D interpolation, i'll be happy to hear
>

Have you looked on netlib.org?

That is the place I'd first look before any other.

John

"Yossi " <yosst@tx.technion.ac.il> wrote in message <hfo95u$23j$1@fred.mathworks.com>...
> "John D'Errico" <woodchips@rochester.rr.com> wrote in message <hfo0pp$clg$1@fred.mathworks.com>...
> > "Yossi " <yosst@tx.technion.ac.il> wrote in message <hflajm$q8s$1@fred.mathworks.com>...
> >
> > > I'm just asking for easy methos to translate interp2.m to cpp file, i just don't want to waste my time on "manual" translation to c++ (i think Matlab compiler can do it). I'm asking in this forum because the issue is a Matlab function called "interp2" and maybe the Matlab compiler could do the job here...
> > >
> >
> > I would be surprised if the matlab compiler would
> > actually make interp2 run significantly faster.
> >
> > A HAND coded version might give you a nice speed
> > gain, but just brute force compilation often does not
> > gain much.
> >
> > John
>
> Thanks John, maybe its not the right place to ask but if you know where i can find in the web a reliable DLL that wraps a C++ implementation of 2D interpolation, i'll be happy to hear

Mirone has two of such. One is a wrapper to GMT's 'surface' and another to MB-sytem's 'mbgrid'. They both use minimum curvature. I don't know how they compare to interp2 since I just do not use interp2 because of its absurd memory requirements.

J. Luis