[Haskell-cafe] some newbie FFI questions

[John Kozak]

Alastair Reid writes:
 > [...]
 > Overall, I'd probably use an unboxed Haskell array.  This would let you get a 
 > memory layout (and memory consumption) close to the normal C layout.  I'd use 
 > access functions to hide the boxing/unboxing and I'd write some 
 > map/fold/scan-like functions to operate on the arrays.
 > 

Thanks (and thanks to the other respondents, too).  Using unboxed
arrays has got my load time down to 15s (from 45), which is OK.  

 > In some cases, I'd leave the object in the C world and access it using FFI 
 > functions and using various convolution operators written in C.  This works 
 > great if you already have a good image processing library, you're not 
 > interested in writing too many new image mangling functions of your own, and 
 > costs of copying the image from C to Haskell (and back again, no doubt), are 
 > excessive.  (I did this some years ago in a real time visual tracking system 
 > that had to deal with 640x512 images coming in at the rate of 30 frames per 
 > second.)

I found your FVision paper a couple of days ago - nice!

John