Thread Subject: MEX inline

Hello,

I am writing a program in matlab which basically runs in a
loop and calls a few MEX functions among other things. (The
loop is the only way I can do it, cannot vectorized more).
When I look a the profiler it seems that matlab spends a lot
of time on function calling. for example one MEX function
ran 1.8 seconds and the entire call took 18 seconds. Is this
a lot of for overhead? Is there a way to accelerate it? for
example my somehow inlining the MEX function?

Thanks,
Sharon

"s a" <shaec47@walla.co.il> writes:

> Hello,
>
> I am writing a program in matlab which basically runs in a
> loop and calls a few MEX functions among other things. (The
> loop is the only way I can do it, cannot vectorized more).
> When I look a the profiler it seems that matlab spends a lot
> of time on function calling. for example one MEX function
> ran 1.8 seconds and the entire call took 18 seconds. Is this
> a lot of for overhead? Is there a way to accelerate it? for
> example my somehow inlining the MEX function?

I don't understand what you mean by your numbers. If one call of the
MEX function takes 1.8 seconds (is that what you mean?), then the
function call overhead is minimal.

MATLAB's function call overhead is substantial (compared to C), but it
is only an issue if there are few operations *inside* the function. If
there are tens of thousands of operations inside the function then the
overhead can probably be neglected.

-Peter

> MATLAB's function call overhead is substantial (compared
to C), but it
> is only an issue if there are few operations *inside* the
function. If
> there are tens of thousands of operations inside the
function then the
> overhead can probably be neglected.
>
> -Peter

The overhead is usually substantial because of allocating
memory, e.g.:
A = mexfcn1(B,C);
A = mexfcn2(A,D);

Now A has to be allocated twice.

Back to the original question: you can of course combine the
mex files, if you have the source code. If not, you have to
be more clear about your program...

Greetz,
Sebastiaan