Re: Optionally make use of 'parallel' in a package

[Olaf Till]

On Thu, Mar 12, 2015 at 01:08:01PM +0100, Daniel Kraft wrote:
> Hi!
> 
> In a package (level-set, to be precise) I want to make use of
> 'pararrayfun' of the parallel package to utilise parallel computation.
> However, I do not want to make level-set strongly dependent on parallel.
>  Instead, I would like to simply fall back to single threading when the
> parallel package is not installed.
> 
> For this, I see two "problems" that I need to solve:
> 
> 1) Decide whether or not a particular package (in this case, 'parallel')
> is installed.  I think this is possible with both the 'pkg' and 'ver'
> functions.  Is there some recommended way to do it?

Package 'optim' currently does it with:

    [desc, state] = pkg ("describe", "parallel");

    if (! strcmpi (state{1}, "loaded"))

      ...

But I'd also be interested to see what others have to say to it.

Olaf

> 2) If present, make sure that 'parallel' is loaded when I need it.  I
> could use 'pkg load' / 'pkg unload' calls in PKG_ADD / PKG_DEL or the
> called function itself.  However, this would mess with the user's
> environment, right?  Is there a way to ensure that the package is loaded
> only temporarily during my function without modifying the global
> environment?
> 
> Thank you a lot!  Yours,
> Daniel
> 
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