[Haskell-cafe] ANNOUNCE: feldspar-language

[Emil Axelsson]

Tom Hawkins skrev:
> On Fri, Nov 6, 2009 at 6:28 AM, Emil Axelsson <emax at chalmers.se> wrote:
> 
>>> I'm trying to get realtime signal processing with Haskell for long. I make
>>> progress, but slowly. Has Ericsson ever thought about using Haskell itself
>>> for signal processing? (But I think they already have Erlang?)
>> No, using Haskell directly is not an option (at least with current compiler
>> technology). Their performance requirements are very high, and the signal
>> processors have quite limited memory, so putting a Haskell RTS on them
>> wouldn't work.
> 
> Atom may be another option.  Though it is not intended for high
> performance DSP, we do use it for basic signal processing.  Here is an
> IIR filter that is used is some fault detection logic on our
> application:
> 
> -- | IIR filter implemented using direct form 2.
> iirFilter :: Name -> Float -> [(Float, Float)] -> E Float -> Atom (E Float)
> iirFilter name b0 coeffs x = do
>   -- Create the filter taps.
>   vs <- mapM (\ i -> float (name ++ show i) 0) [1 .. length coeffs]
>   -- Cascade the filter taps together.
>   mapM_ (\ (vA, vB) -> vA <== value vB) $ zip (tail vs) vs
>   -- Calculate the input to the chain of taps.
>   let w0 = sum ( x :  [ (value v) * Const (-a) | (v, (a, _)) <- zip vs coeffs ])
>       bs = b0 : (snd $ unzip coeffs)
>       ws = w0 : map value vs
>       us = [ w * Const b | (w, b) <- zip ws bs ]
>   head vs <== w0
>   -- Return the output.
>   return $ sum us
> 
> http://hackage.haskell.org/package/atom

Nice!

One of our project members has been looking at Atom, not for numerical 
computations, but for real-time scheduling (which Feldspar should deal 
with eventually).

What kind of code (in terms of efficiency) does the above description 
compile to?

/ Emil