I was trying out some of the ArBB code samples. And thought of writing a simple application to use arbb add_reduce function. I'm running Windows 7, Intel Core 2 Duo CPU : E7500, 2.93 GHz.
Running my sample gives me a speedup of just 1.6x on 2 cores by setting ARBB_OPT_LEVEL=O3.
Here is the code :