[Users] update new user guide for non-TeraGrid/XSEDE users?

[Erik Schnetter]

On Wed, Aug 24, 2011 at 9:55 AM, Frank Loeffler <knarf at cct.lsu.edu> wrote:
> Hi,
>
> On Wed, Aug 24, 2011 at 03:47:15PM +0200, Ian Hinder wrote:
>> Would it be useful for each thorn to declare in its configuration.ccl file whether it supports OpenMP or not?  Then at least Cactus could abort if you try to run a thorn which does not support OpenMP with more than one thread per process.
>
> A simulation often contains a large number of thorns. Most of them don't
> contain computationally intensive code. They don't need to be
> parallelized with openmp, or at least it wouldn't be a big problem if
> they were not. Instead of marking thorns as openmp-ready I would rather
> mark thorns as "don't use with openmp". This then wouldn't even need to
> be implemented in simfactory. The flesh has that information and can set
> the corresponding openmp variables at startup, disregarding whatever the
> environment specifies otherwise. If course, this mechanism would have to
> have an off-switch as well, disregarding the information in the thorns
> then.

The flesh doesn't know how many threads to use on a particular
machine. The flesh also doesn't know whether the user started a
certain number of MPI processes on a node, from which follows the
number of threads to use.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/