[Haskell] Control.Monad.Writer as Python generator

[ChrisK]

You are correct.  Moand.Cont yield even runs without -O optimizing, 
just slower:

Monad.Writer counts 10^9 zeros in 99 seconds (user time)
Monad.Cont counts 10^8 zero in 35 seconds user time.
So the writer is 3.5 times faster without '-O'

With -O
Monad.Writer counts 10^9 zeros in 105 seconds
Monad.Cont counts 10^8 zeros in 11 seconds, 10^9 zeros in 110 seconds.

So with '-O' they are the same speed.  Nice.

Anyone have an idea why ghci can't garbage collect it?
Is this an actual bug or an innate quirk of the REPL ?

-- 
Chris

On Apr 15, 2005, at 12:43 AM, Cale Gibbard wrote:

> However, after compiling with optimisations turned on, there is no
> such problem with the continuation-based version, memory usage appears
> constant.
>
>  - Cale
>
> On 4/14/05, ChrisK <chrisk at mit.edu> wrote:
>> Thanks for the Cont example, David.  But...
>>
>> The MonadCont is clever and it works ... but then fails -- ghci does
>> not garbage collect and it blows up.
>> With the MonadCont version I can count up to 10^7 zeros:
>>
>> *Main> length $ take (10^7) zerosInf
>> 10000000
>> (26.20 secs, 0 bytes)
>>
>> But this increases RSIZE of ghc-6.4 to 165MB.  The 10^8 version goes 
>> to
>> swap space and I had to kill it.  My original MonadWriter version does
>> not increase RSIZE when run (constant space), so the garbage 
>> collection
>> must be working, and it is O(N) in the # of zeros counted:
>>
>> *Main> length $ take (10^7) zerosInf
>> 10000000
>> (1.22 secs, 0 bytes)
>> *Main> length $ take (10^8) zerosInf
>> 100000000
>> (10.05 secs, 0 bytes)
>> *Main> length $ take (10^9) zerosInf
>> 1000000000
>> (109.83 secs, 6 bytes)
>>
>> --
>> Chris
>>