integral from 0 to 1  f(x)=sqrt(1-(x-1)^2); acc=eps= 1e-8
estimated integral *4 =	 3.141592654015791 
pi                    =	 3.141592653589793 
estimated error       =	 1.785398163503948e-8 
actuall error         =	 4.2599790361919077e-10 
npoints= 3886