Cache lines, false sharing and alignment

Question

I wrote the following short C++ program to reproduce the false sharing effect as described by Herb Sutter:

Say, we want to perform a total amount of WORKLOAD integer op

Answer 1

gcc supports an aligned keyword: http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html

You probably want something like this:

int arr[PARALLEL * 16] __attribute__ ((aligned (8)));

This aligns arr to an eight-byte boundary.

Visual Studio has a similar feature, too: http://msdn.microsoft.com/en-us/library/83ythb65.aspx