Problem in sampling a binary variable from a PRNG

[malie]

Hi, I'm running into a problem when sampling from a vector of probabilities, to get a vector of booleans.

The program fails at runtime: Prelude.Ord.< applied to EDSL types: use (<*) instead

The code is at https://github.com/haskell-munich/accelerate-rbm/blob/master/Main.hs#L61

I built my own (very simple) PRNG that produces integers from 0 to 1023. The probabilities are from 0.0 to 1.0, so a <* should do the job (after scaling and flooring).

First I tried building a PRNG that produces random numbers between 0.0 and 1.0. That failed also at runtime. The fromIntegral, which I wanted to use to turn the Int64 into a Float, stopped. I'll reconstruct that if it's helpful tomorrow.

Do you have examples that use PRNGs to sample from probabilities?

Thanks, Markus

[tmcdonell]

Use floor from Data.Array.Accelerate.

You might find it useful to, instead of the explicit import and hiding lists that you have, use:

import Prelude               as P
import Data.Array.Accelerate as A

And then when you try to use something defined in both (such asfloor) ghc will tell you there are two available, and it will be obvious to pick A.floor in this case.

[malie]

That's great! Many thanks. With correct imports I also get the version working that generates random floats from 0.0 to 1.0.