cache optimization
£ukasz
blurrpp@yahoo.com
Thu Nov 26 13:14:00 GMT 2009
Hi I want to learn how to optimaze cache usage in gcc. I find builtin function __builtin_prefetch which should prefetch datas to cache .. so i use cannonical :) example of vector addition.
for (i = 0; i < n; i++)
{
a[i] = a[i] + b[i];
__builtin_prefetch (&a[i+1], 1, 1);
__builtin_prefetch (&b[i+1], 0, 1);
/* ... */
}
and compile it with gcc without special options .... but its slower than
for (i = 0; i < n; i++)
{
a[i] = a[i] + b[i];
/* ... */
}
so maybe I should compile it with soem extra options to have advantage of cache prefatching ?(-fprefetch-loop-array doenst works )
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