Re: [eigen] Help on solving a race condition

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

OK, sorry my naivety, this is well explained here:

http://blogs.msdn.com/b/oldnewthing/archive/2004/03/08/85901.aspx

still looking for an elegant solution though.

gael

On Fri, Jun 8, 2012 at 3:12 PM, Gael Guennebaud
<gael.guennebaud@xxxxxxxxx> wrote:
> Hi,
>
> I'm looking for some help on understanding how the following piece of
> code in Eigen can lead to a race condition when the function
> manage_caching_sizes is called from different threads:
>
>
> inline std::ptrdiff_t manage_caching_sizes_helper(std::ptrdiff_t a,
> std::ptrdiff_t b)
> {
>  return a<=0 ? b : a;
> }
>
> inline void manage_caching_sizes(Action action, std::ptrdiff_t* l1=0,
> std::ptrdiff_t* l2=0)
> {
>  static std::ptrdiff_t m_l1CacheSize =
> manage_caching_sizes_helper(queryL1CacheSize(),8 * 1024);
>  static std::ptrdiff_t m_l2CacheSize =
> manage_caching_sizes_helper(queryTopLevelCacheSize(),1*1024*1024);
>  ...
> }
>
>
> During it's first call, this function computes and store the cache sizes.
>
> I would like to find a solution that avoids making the static variable
> "thread private" as suggested there:
> http://stackoverflow.com/questions/8828466/using-openmp-and-eigen-causes-infinite-loop-deadlock/10540025
> The problem with this approach, is that the cache-sizes are recomputed
> for every thread.
>
>
> thanks,
>
> Gaël