Apple MacBook Pro (Intel Core 2 Duo)
Mac OS X Snow Leopard
g++ 4.2

$ make
g++ -c main.cpp -O3 -m32
g++ -c simpson_virt.cpp -O3 -m32
g++ -c functions.cpp -O3 -m32
g++ main.o simpson_virt.o functions.o -o simpson -lm -O3 -m32

$ ./simpson 
Function pointer: 1.92057
Functor: 0.730102
Virtual: 2.23962