When benchmarking programs on linux systems I find cache effects dominate.
ie. On current systems the difference in speed between RAM and disk is so vast... that 2 orders of magnitude differences in algorithms can be swallowed entirely by whether the data is in a ram disk buffer or on disk. So linux has a way of flushing clean caches.... echo 3 > /proc/sys/vm/drop_caches For example... cat the cat program to /dev/null twice to make the cache "hot", measure the time on a "hot" cache. Then sync and drop the caches and do it on a cold cache. cat /bin/cat > /dev/null;time cat /bin/cat > /dev/null;sync;sudo bash -c 'echo 3 > /proc/sys/vm/drop_caches';time cat /bin/cat > /dev/null real 0m0.002s user 0m0.000s sys 0m0.004s real 0m0.172s user 0m0.000s sys 0m0.008s 86x slower! John Carter Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : john.car...@tait.co.nz New Zealand
