takes about 1.7 hours. Big Crush takes about 4 hours. For a more complex RNG, all these times increase by a factor of two or more. For comparison, the Diehard tests take about 15 seconds to run. Limitations TestU01 only accepts 32-bit inputs, and interprets them as values in the range [0, 1]. This causes it to be more sensitive to flaws in the most-significant bits than the least significant bits. It is important to test general-purpose generators in bit-reversed form, to verify their suitability for applications which use the low-order bits. Generators which produce 64 bits of output additionally require separate tests for their high and low halves. See also Randomness tests Diehard tests PractRand References Computer libraries Random number generation Statistical software