Re: Random Number Update

Carter, I obviously didn’t explain myself very well. We can decouple removing the “bad” RNG from the replacement of it with a “good” RNG. As I thought I said, any new RNG should have the same status as every other RNG and then people can choose; there is no “blessed” RNG. It seems simple (to me at any rate) to decouple these. More power to your elbow on creating an RNG but I don’t think there should be anything “official” about it. I’ll say it again: I don’t think there should be a random v2 but a random-foobar where foobar is your algorithm. What do you see sub-optimal about deprecating something that is clearly broken? I believe I have done my bit for the Haskell Community in trying to resolve what is a tedious situation. I suggest we await the view of the Core Libraries Committee assuming they still see this as part of their scope and take it from there. Dominic.

On 24 Jan 2017, at 15:33, Carter Schonwald wrote:

Dominic, if you want to remove yourself from maintainer hood that's cool.

I'm keen on finishing up my random v2 release which is a much improved breaking Change.

I spent part of my holiday this year working on it.

Dominic: I'm confused and surprised by your email after we had a one hour phone chat about this topic last week.

I'm disappointed you are still raising concerns I addressed and explained to you last week.

Random v2 is in flight. You are welcome to stop being involved.

On Tue, Jan 24, 2017 at 10:19 AM Adam Bergmark mailto:adam@bergmark.nl> wrote: On Tue, 24 Jan 2017 at 14:36 Dominic Steinitz mailto:dominic@steinitz.org> wrote: I wanted to give an update on the status of random numbers in Haskell.

1. It is well known that the random number generator package

https://hackage.haskell.org/package/random https://hackage.haskell.org/package/random gives unexpected

results.

2. Most people do *not* use it. I believe

https://hackage.haskell.org/package/mwc-random https://hackage.haskell.org/package/mwc-random is a popular choice

but developers are free to use e.g. Mersenne Twister, PCG

(Permuted Congruential Generator), TF (ThreeFish) and many others.

3. Approximately 2 years, I made a proposal to replace the algorithm

within random (https://hackage.haskell.org/package/random https://hackage.haskell.org/package/random) with

that used by tf-random

(https://hackage.haskell.org/package/tf-random https://hackage.haskell.org/package/tf-random) which is used by

QuickCheck. In summary, the response to this was that someone

should do more research with the result that nothing happened.

4. In the meantime, random

(https://hackage.haskell.org/package/random https://hackage.haskell.org/package/random) is *no longer* a core

library. It's just a library with the same status as

e.g. mwc-random. However, it has one difference: it uses the name

for its module: "System.Random". Other RNGs use

"System.Random.MWC", "System.Random.PCG", "System.Random.Mersenne"

etc.

As a maintainer of random

(https://hackage.haskell.org/package/random https://hackage.haskell.org/package/random), my proposal now is to

deprecate all of it.

I am not clear what the policy is on namespace usage. Could every RNG

use the module name "System.Random"? Or is this somehow reserved? If

the latter then I propose that *nothing* uses this name and that all

RNGs should add a suffix indicating which algorithm they use.

They *could* use the same namespace but I don't recommend it. If someone depends on two of these packages they would have to use PackageImports. Tools such as doctest break if a package db has module conflicts, even if only one of the packages is listed as a dependency.

Cheers, Adam

I note that the Haskell Platform contains tf-random so users of this

will still be able to generate (better) random numbers.

If someone comes along in the future, as I hope they do, and

implements e.g. Guy Steele's splitmix algorithm then this can occupy

the name "System.Random.Splitmix" and have the package name

"random-splitmix".

The advantages of doing this are:

1. Neophyte (and experienced) Haskellers do not accidentally use an

RNG which gives unexpected results.

2. No-one will any longer be able to write blogs or papers about this

embarrassing aspect of Haskell.

I believe the co-maintainer of random

(https://hackage.haskell.org/package/random https://hackage.haskell.org/package/random), Carter Schonwald, has a

different view on this matter but it is best he speaks for himself

rather than me imperfectly trying to reflect his thinking.

Dominic Steinitz

dominic@steinitz.org mailto:dominic@steinitz.org

http://idontgetoutmuch.wordpress.com http://idontgetoutmuch.wordpress.com/

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