N=1E+08
Running hsum in 2 threads in parallel:
	hsum: from 5E+07 to 1E+08 is 0.6931472
	hsum: from 1 to 5E+07 is 18.30475
	Main: hsum from 1 to 1E+08 is 18.9979
	time: 2.991 sec
Running hsum in 1 thread:
	hsum: from 1 to 1E+08 is 18.9979
	time: 5.822 sec
Calculating sum in 4 threads via Parallel.For:
	Main: hsum from 1 to 1E+08 is 18.9979
	time: 8.556 sec