On Thursday, 18 October 2018 at 17:01:46 UTC, Stanislav Blinov
wrote:
On Thursday, 18 October 2018 at 16:31:33 UTC, Vijay Nayar wrote:
Imagine a simple algorithm that does logic on very long
numbers, split into bytes. One multi-threaded implementation
may use 4 threads. The first operating on bytes 0, 4, 8, etc.
The second operating on bytes 1, 5, 9, etc.
In this case, a mutex or lock isn't actually needed, because
the algorithm itself assures that threads don't collide.
Yes, they do collide. You just turned your cache into a giant
clusterf**k. Keyword: MESIF.
In that case partitioning in cache line sizes is the least that
has to be done.
