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# New random-number generator—64-bit Mersenne Twister

## Highlights

• 64-bit Mersenne Twister
• Extremely long period—219937 − 1
• 623-dimensionally equidistributed
• 53-bit resolution
• Applies to all new random-number functions
• For uniform variates
• runiform(a,b)
• runiformint(a,b)
• For logistic variates
• rlogistic()
• rlogistic(s)
• rlogistic(m,s)
• For Weibull variates
• rweibull(a,b)
• rweibull(a,b,g)
• For Weibull (proportional hazards) variates:
• rweibullph(a,b)
• rweibullph(a,b,g)
• For exponential variates
• rexponential(b)
• And existing random-number functions
• For uniform variates
• runiform()
• For normal variates
• rnormal()
• rnormal(m,s)
• And more
• rbeta(a,b)
• rbinomial(n,p)
• rchi2(df)
• rgamma(a,b)
• rhypergeometric(N,K,n)
• rnbinomial(n,p)
• rpoisson(m)
• rt(df)

## What's this about?

Stata now uses the 64-bit Mersenne Twister (MT64) as its default random-number generator. Stata previously used the 32-bit KISS generator (KISS32), and still does under version control. KISS32 is an excellent random-number generator, but the Mersenne Twister has even better properties.

The MT64 is currently the most widely used random-number generator. It has a much larger period than the majority of random-number generators, meaning that you can run simulations of simulations of simulations without ever drawing the same random numbers. In addition, the MT64 generator requires 623 dimensions to exhibit patterns.

## Let's see it work

Suppose we wish to generate 1,000 observations from a Weibull(3,1) distribution. We first set the number of observations and then set the seed for reproducibility.

. set obs 1000 . set seed 2414830


We then generate our new variable. To see the results, we summarize it.

. generate weib_mt64 = rweibull(3,1)

. summarize weib_mt64

Variable          Obs        Mean    Std. Dev.       Min        Max

weib_mt64       1,000     .907414    .3235842   .1243035   1.930414


## Tell me more

For more information about the Mersenne Twister, see Methods and formulas.

To learn more about Stata's new random-number functions and the statistical distribution functions that accompany them, see Statistical distribution functions.

To find out more about all of Stata's Random-number functions, see the new 151-page Stata Functions Reference Manual.

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