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

C++ itself doesn't "care" about CPU caches, so there's no support for querying cache-sizes built into the language. If you are developing for Windows, then there's the GetLogicalProcessorInformation()-function, which can be used to query information about the CPU caches.

Answer 2

Preallocate a large array. Then access each element sequentially and record the time for each access. Ideally there will be a jump in access time when cache miss occurs. Then you can calculate your L1 Cache. It might not work but worth trying.

Answer 3

Interestingly enough, I wrote a program to do this awhile ago (in C though, but I'm sure it will be easy to incorporate in C++ code).

http://github.com/wowus/CacheLineDetection/blob/master/Cache%20Line%20Detection/cache.c

The get_cache_line function is the interesting one, which returns the location of right before the biggest spike in timing data of array accesses. It correctly guessed on my machine! If anything else, it can help you make your own.

It's based off of this article, which originally piqued my interest: http://igoro.com/archive/gallery-of-processor-cache-effects/

Answer 4

read the cpuid of the cpu (x86) and then determine the cache-size by a look-up-table. The table has to be filled with the cache sizes the manufacturer of the cpu publishes in its programming manuals.