MersenneTwister, srand

digxx

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Oct 28, 2016, 12:59:53 PM10/28/16

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So what is the difference between srand and merseentwister?

when I do:

r=srand(0)

I get the same as

r=MersenneTwister(0)

and also how do I get my random numbers

what do the different fields mean?

e.g.

julia> r.(1)

1-element Array{UInt32,1}:

0x00000000

julia> r.(2)

Base.dSFMT.DSFMT_state(Int32[748398797,1073523691,-1738140313,1073664641,-1492392947,1073490074,-1625281839,1073254801,1875112882,1073717145 … 943540191,1073626624,1091647724,1073372234,-1273625233,-823628301,835224507,991807863,382,0])

julia> r.(2).(1)

770-element Array{Int32,1}:

748398797

1073523691

-1738140313

1073664641

-1492392947

1073490074

-1625281839

1073254801

1875112882

1073717145

-147366646

1073379643

-822088544

1073057897

-172354

1073036393

-1801109415

1073061557

-1726958192

1073632729

-309172420

1073464042

-354763249

1073128395

135648219

1073687628

92195370

1073342927

-87798830

1073300027

446697077

1073397042

-1348144529

1073439833

-64993866

1073659055

-992725433

1073226916

348453421

1072702220

⋮

1073417805

-1607069797

1072770558

118292460

1073306270

-572602520

1073370707

-445536129

1073393538

1989954253

1073598613

986054037

1073137169

1796020743

1073612929

161145485

1073732406

-773274735

1072720842

1219081491

1073737258

1793984938

1072858519

-1584606890

1072715174

-1892075178

1073622009

-183639381

1072906897

943540191

1073626624

1091647724

1073372234

-1273625233

-823628301

835224507

991807863

382

0

julia> r.(3)

382-element Array{Float64,1}:

0.0

⋮

0.0

julia> r.(4)

382

The number I had in my head for MersenneTwister was 624 but I dont find it anywhere?

Do I only initialize the pseudo random number generator this way and the actual "random" number is then obtain by rand(1) for example?

How do I acutally set the seed coz when I do

srand(0) and rand() would actually be a mersennetwister I'd expect zeros everywhere...

Thx

digxx

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Oct 28, 2016, 1:23:14 PM10/28/16

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With number in my head I meant, that I expected to see random number arrays of size 624 since as far as I know they are created simultaneously,right?

Isaiah Norton

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Oct 28, 2016, 1:53:31 PM10/28/16

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http://docs.julialang.org/en/latest/stdlib/numbers/?highlight=global_rng#random-numbers

digxx

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Oct 28, 2016, 2:11:46 PM10/28/16

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Sorry but that doesn't answer my question. That's where I have the calling from but it does not explain the output and what it means...

Isaiah Norton

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Oct 28, 2016, 2:37:08 PM10/28/16

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So what is the difference between srand and merseentwister?

Per doc link, srand uses MT by default.

and also how do I get my random numbers

rand() for floats less than 1 by default, or specify a set to choose from:

help?> rand
search: rand randn rand! randn! randexp randperm randjump randexp! randcycle randsubseq randstring randsubseq! RandomDevice srand sprand sprandn sprandbool bitrand transcode

rand([rng=GLOBAL_RNG], [S], [dims...])

Pick a random element or array of random elements from the set of values specified by S; S can be

• an indexable collection (for example 1:n or ['x','y','z']), or

• a type: the set of values to pick from is then equivalent to typemin(S):typemax(S) for integers (this is not applicable to BigInt), and to [0, 1) for floating point numbers;

what do the different fields mean?

The fields aren't intended to be accessed, but you can see each element name with:

julia> fieldnames(MersenneTwister)
4-element Array{Symbol,1}:
:seed
:state
:vals
:idx

How do I acutally set the seed

srand

srand(0) and rand() would actually be a mersennetwister I'd expect zeros everywhere...

Why?

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