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srand

srand([rng], [seed])

Reseed the random number generator. If a seed is provided, the RNG will give a reproducible sequence of numbers, otherwise Julia will get entropy from the system. For MersenneTwister, the seed may be a non-negative integer, a vector of UInt32 integers or a filename, in which case the seed is read from a file. RandomDevice does not support seeding.

Examples

1. Reseed the default random number generator:

   julia> srand(123)
   MersenneTwister(UInt32[0x0000007b], Random.DSFMT.DSFMT_state(Int32[578991598, 1073482918, 160911997, 1073181524, -1591984238, 1073033171, 8755, 1073033138, -32137, 1073033159  …  1073033196, 1, 0, -1, 0, 0, 0, 0, 0, 0]), [1.5])
   
   julia> rand()
   0.7680393370123325

   In this example, srand(123) seeds the default random number generator, MersenneTwister, with the seed value 123. Subsequent calls to rand() will produce the same sequence of random numbers.

2. Reseed a specific random number generator:

   julia> rng = RandomDevice()
   RandomDevice()
   
   julia> srand(rng, 42)
   MersenneTwister(UInt32[0x0000002a], Random.DSFMT.DSFMT_state(Int32[1348295911, 1073479697, 160910911, 1073078005, -1591984080, 1073033129, 8755, 1073033138, -32137, 1073033159  …  1073033196, 1, 0, -1, 0, 0, 0, 0, 0, 0]), [1.5])
   
   julia> rand(rng)
   0.1577570229065424

   Here, srand(rng, 42) reseeds a specific random number generator (rng in this case) with the seed value 42. Subsequent calls to rand(rng) will produce a reproducible sequence of random numbers using the specified generator.

Common mistake example:

julia> srand("random_seed.txt")
ERROR: MethodError: no method matching srand(::String)

In this example, the srand function is called with a string argument. However, srand does not accept a string as a seed. Make sure to provide a valid seed value, such as an integer or a vector of UInt32 integers, when using srand.

See Also

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