[Boost-users] Threads example question

I'm trying to learn how to use Boost.Threads with this example: http://pastebin.ca/1472832 On Ubuntu 8.04 with Boost 1.34 I'm compiling with a makefile like this: t1: t1.o g++ t1.o /usr/lib/libboost_thread-mt.so -o t1 t1.o: t1.cpp g++ -I /usr/include/boost/ -c t1.cpp However I get very similar execution times for the single-threaded version and the one which creates two threads. What am I doing wrong? thanks, Anders W