Andrew Coppin wrote:
> Andrew Coppin wrote:
>> copy :: Word32 -> IOUArray Word32 Bool -> Word32 -> IO (IOUArray
>> Word32 Bool)
>> copy p grid size = do
>> let size' = size * p
>> grid' <- newArray (1,size') False
>>
>> mapM_
>> (\n -> do
>> b <- readArray grid n
>> if b
>> then mapM_ (\x -> writeArray grid' (n + size*x) True) [0..p-1]
>> else return ()
>> )
>> [1..size]
>>
>> return grid'
>
> Actually, thinking about this... for most kinds of arrays (whether boxed
> or unboxed, mutable or immutable) there's probably a more efficient way
> to copy the data then this. Maybe we should add something to the various
> array APIs to allow efficient copying of arrays / large chunks of arrays?
>
> (In the case of an unboxed array of bits, you can probably copy whole
> 32-bit or 64-bit words with a few machine instructions, for example.)
For GHC 6.6 I created
> foreign import ccall unsafe "memcpy"
> memcpy :: MutableByteArray# RealWorld -> MutableByteArray# RealWorld ->
> Int# -> IO ()
> {-# INLINE copySTU #-}
> copySTU :: (Show i,Ix i,MArray (STUArray s) e (ST s)) => STUArray s i e ->
> STUArray s i e -> ST s ()
> copySTU (STUArray _ _ msource) (STUArray _ _ mdest) =
> -- do b1 <- getBounds s1
> -- b2 <- getBounds s2
> -- when (b1/=b2) (error ("\n\nWTF copySTU: "++show (b1,b2)))
> ST $ \s1# ->
> case sizeofMutableByteArray# msource of { n# ->
> case unsafeCoerce# memcpy mdest msource n# s1# of { (# s2#, () #) ->
> (# s2#, () #) }}
To allow efficient copying of STUArrays.
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