Word Tearing: Still a practical problem?

[nedbrek]

Hello all,

"dsimcha" <dsimcha at yahoo.com> wrote in message 
news:im8d3b$j78$1 at digitalmars.com...
>A few posts deep in the discussion on std.parallelism have prompted me to
> double-check an assumption that I made previously.  Is writing to adjacent 
> but
> non-overlapping memory addresses concurrently from different threads safe 
> on
> all hardware we care about supporting?
>
> I know this isn't safe on some DS9K-like architectures that we don't care
> about, like old DEC Alphas.  This is because the hardware doesn't allow
> addressing of single bytes.  I'm also aware of the performance 
> implications of
> false sharing, but this is not of concern because, for the cases where
> adjacent memory addresses are written to concurrently in std.parallelism 
> or
> its examples, these are only a tiny fraction of writes and would not have 
> a
> significant impact on performance.

The main architectures (x86 and ARM) are both byte granular.  Most embedded 
platforms are also byte granular.  Alpha is the only architecture I am aware 
of that had this problem.  Possibly other old/high performance ones... 
(Cray, 360, etc.)

Ned