sav = 0; iter = 10000000;
For[i = 1, i <= iter, i++,
If[Random[]^2 < 1/2, sav = sav + 1;]
] // Timing
2 sav/iter // N
这样居然也算了23秒，觉得有点太久，请问要怎样写才会快呢?

Nest[UnitStep[(1/2-Random[]^2)]+#&,0,10000000]

RandomVariate[NormalDistribution[1/Sqrt[2], 1/Sqrt[12]//Sqrt[10000000]]]

AbsoluteTiming@Total@NestList[If[Random[]^2<0.5,1,0]&,0,iter]