Hi,
Since I discovered that my program spent most of its time reading and
writing files, I had a go at transforming it from using readFile to
using array IO.
Since my file consists of lines of length 18, I tried writing a
similar function to readFile, to return a lazy list of lines as
arrays, included below. This works, but wasn't more efficient. I
haven't toyed to much with this kind of thing before, so please let me
know if I'm doing anything obviously stupid.
Perhaps the whole strategy is wrong? Should I wrap more of my program
in IO, and do things incrementally there? (The files can be large,
typically 100M-2G range, so reading them strictly is not an option)
Or would it be more efficient to read larger chunks at a time? If so,
what is a good chunk size? 1K? 4K? 1M?
----------8<--------------------
-- read the external file as a lazy list of arrays
readXFile :: FilePath -> IO [UArray Int Word8]
readXFile f = do
h <- openFile f ReadMode
getArrays h
where getArrays h = do end <- hIsEOF h
case end of
True -> return []
False -> do
(a :: IOUArray Int Word8) <- newArray (0,17) 0
hGetArray h a 18
a' <- unsafeFreeze a
as <- unsafeInterleaveIO (getArrays h)
return (a':as)
----------8<--------------------
-kzm
--
If I haven't seen further, it is by standing in the footprints of giants
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