C++ cache aware programming

Question

is there a way in C++ to determine the CPU\'s cache size? i have an algorithm that processes a lot of data and i\'d like to break this data down into chunks such that they f

Answer 1

IIRC, GCC has a __builtin_prefetch hint.

http://gcc.gnu.org/onlinedocs/gcc-3.3.6/gcc/Other-Builtins.html

has an excellent section on this. Basically, it suggests:

__builtin_prefetch (&array[i + LookAhead], rw, locality);

where rw is a 0 (prepare for read) or 1 (prepare for a write) value, and locality uses the number 0-3, where zero is no locality, and 3 is very strong locality.

Both are optional. LookAhead would be the number of elements to look ahead to. If memory access were 100 cycles, and the unrolled loops are two cycles apart, LookAhead could be set to 50 or 51.