Re: 'import ccall unsafe' and parallelism

glad I could help, https://github.com/wellposed/hblas/blob/master/src/Numerical/HBLAS/BLAS/Inte... is an example of the "choose to do the safe vs unsafe ffi call" trick in the case of blas / lapack routines, i can always estimate how long a compute job will take as a function of its inputs, and i use that estimate to decide which ffi strategy to use (ie i use unsafe ffi on < 10 microsecond computations so that the overhead doesn't dominate the compute time on tiny inputs) On Thu, Aug 14, 2014 at 5:38 PM, Christian Höner zu Siederdissen < choener@tbi.univie.ac.at> wrote:

That's actually a great idea, especially since the safe variants of the calls are already in place.

* Carter Schonwald [14.08.2014 23:10]:

...

have a smart wrapper around you ffi call, and if when you think the ffi call will take more than 1 microsecond, ALWAYS use the safe ffi call, i do something like this in an FFI i wrote, it works great

On Thu, Aug 14, 2014 at 1:20 PM, Christian HAP:ner zu Siederdissen wrote:

Thanks,

I've played around some more and finally more than one capability is active. And indeed, unsafe calls don't block everything. I /had/ actually read that but when I saw the system spending basically only 100% cpu time, I'd thought to ask.

One problem with this program seems to be that the different tasks are of vastly different sizes. Inputs range from ~ 7x10^1 to ~ 3x10^7 elements inducing waits with the larger problem sizes.

We'll keep the program single-threaded for now as this also keeps memory consumption at only 25 gbyte instead of the more impressive 70 gbyte in multi-threaded mode ;-)

Viele Gruesse, Christian

_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users