Re: Random Number Update

Point being: you are welcome to remove yourself from the maintainers set for random. On Tue, Jan 24, 2017 at 10:33 AM Carter Schonwald < carter.schonwald@gmail.com> 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 wrote:

On Tue, 24 Jan 2017 at 14:36 Dominic Steinitz 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 gives unexpected

results.

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

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) with

that used by 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) 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), 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), 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

http://idontgetoutmuch.wordpress.com

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