Matlab interface

[gerald...@gmail.com]

Hi,

is there a way to call a golang function within a Matlab environment. I know what you can call C/C++ functions within Matlab...

Thanks,

Gerald

[Maxim Khitrov]

You can call into MATLAB from Go via cgo, but not the other way
around. Here's some relevant documentation:

http://www.mathworks.com/help/matlab/calling-external-functions.html
http://www.mathworks.com/help/matlab/programming-interfaces-for-c-c-fortran-com.html

- Max

[Gerald Stanje]

Yes, matlab supports c/c++ function calls...
But you could call a golang function from c?

Sent from my iPhone

[Maxim Khitrov]

Not unless something has changed recently with the runtime. You can
make Go -> C -> Go calls, but not C -> Go. In other words, the Go
runtime needs to be the first thing to run. Of course, you can create
a separate Go executable and communicate with it through files,
network, or any other IPC mechanism.

[gerald...@gmail.com]

yes...runtime does gc and other stuff...

i see that matlab can call java code using JMI....could that be applied to golang too?

[Maxim Khitrov]

If the developers decide to implement a way of initializing the
runtime from C, then it would be possible. I don't think there are any
plans to do that at the moment.

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[gerald...@gmail.com]

what IPC technique would you choose between matlab and golang if speed matters?

sockets?

from what i see matlab can do sockets...

another way is: call the executable from matlab...i guess thats rather slow?

[Maxim Khitrov]

It depends entirely on what you're trying to do and whether you mean
speed as in latency or throughput. You could use memory maps, as in
the following example:

http://www.mathworks.com/help/matlab/import_export/share-memory-between-applications.html

Network is another option, calling an executable may also work. For
anything that you can't do directly in MATLAB, you can compile mex
functions from C or write your own Java classes.

[Gerald Stan]

thats what I already did...

calling a simple hello_world executable takes around 400ms...

so looking for another option...

im not sure if golang can do memory maps!?

so sockets would be the best option i guess...

Maxim Khitrov:

I would start with something simple, like using the system function to
run your Go binary and passing data via stdin/stdout or files, measure
the performance, and then move on to more complicated methods, if
needed.

2014-09-02 20:16 GMT+02:00 Maxim Khitrov <m...@mxcrypt.com>:

I would start with something simple, like using the system function to
run your Go binary and passing data via stdin/stdout or files, measure
the performance, and then move on to more complicated methods, if
needed.

On Tue, Sep 2, 2014 at 1:38 PM, Gerald Stan <gerald...@gmail.com> wrote:
> i do some parsing with golang...matlab sends the text to be parsed to
> golang, go does the parsing and needs to send it back to matlab...
> i need an option with low latency...
>
> yeah, but i cant compile my go source with mex...

[Maxim Khitrov]

I just tested this by running "tic; system('hello'); toc" and got ~50ms on Windows and ~5ms on Linux with MATLAB R2014a. Not sure why you're getting 400ms. Either way, if you need even lower latency, then the Go process has to be running already when MATLAB submits the request.

For memory maps see http://golang.org/pkg/syscall/#Mmap. If you are on *nix, mkfifo might be another option.

[gerald...@gmail.com]

here my test:

golang:

http://play.golang.org/p/x3AOQxSB7C

matlab:

clear;

clc;

tic;

[status, result] =  system(['goapp.exe -s hello']);

toc;

[gerald...@gmail.com]

ok, i some more measurements now:

- Elapsed time call system('dir') from matlab is ~0.199997 seconds.

- Elapsed time call my app and pass a parameter is ~0.752352 seconds: ... does that sound reasonable on windows x32?

tic

[status, result] = system('goapp.exe -name=test');

result

toc

here the goapp:

http://play.golang.org/p/vvC4zDO8hH

[Maxim Khitrov]

I ran your goapp.exe 100 times using the same MATLAB commands on Windows 7 64-bit and got a mean time of 0.062 seconds. I don't know what hardware you're using, but 0.752 seems a bit slow. Do you have some antivirus that might be doing a scan of the executable every time you run it? I don't have any other suggestions and at this point the issue is related more to MATLAB than to Go.

[gerald...@gmail.com]

I didnt see that the executable was on a network drive. ;) ...getting similar times now.

[gerald...@gmail.com]

[gerald...@gmail.com]

seems shared libraries are in plan and could be used in non go programs a a plugin:

https://docs.google.com/document/d/1nr-TQHw_er6GOQRsF6T43GGhFDelrAP0NqSS_00RgZQ/edit#heading=h.fwmrrio0df0i

what do you think?

[brainman]

On Thursday, 4 September 2014 04:13:14 UTC+10, gerald...@gmail.com wrote:

I didnt see that the executable was on a network drive. ;) ...getting similar times now.

Also remember that Windows must search your PATH for the executable. 

Alex