Den 19.02.2011 18:13, skrev Sebastian Haase: > Can one assume that the cache line is always a few mega bytes ?
Don't confuse the size of a cache with the size of a cache line. A "cache line" (which is the unit that gets marked dirty) is typically 8-512 bytes. Make sure your OpenMP threads stay off each others cache lines, and it will scale nicely. For example, you can specify a chunk-size to the "schedule" pragma to force them apart; it applies to the loop index, so you must do calculations for the block size on the shared write buffer. If you use reduction(+:dist) the write buffer will be completely private, but you get summations after the loop. That is the limited amount of control you get with OpenMP. pthreads will give you better control than OpenMP, but are messy and painful to work with. With MPI you have separate processes, so everything is completely isolated. It's more difficult to program and debug than OpenMP code, but will usually perform better. Sturla _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
