On 02 September 2005 17:09, Bulat Ziganshin wrote:
Hello Alistair,
Thursday, September 01, 2005, 6:36:09 PM, you wrote:
The heap profile graph for this program shows an initial peak, and then the graph is flat at 8Mbytes, which I think is the space allocated to the two STArrays (2 arrays, 1 million chars each, 4 bytes per char?). So it looks as though any allocation for the loop function is GC'd very soon after it's allocated.
Char uses 4 bytes because it must hold any Unicode character, which is about 1 million :) use Word8 or CChar
STArray is a lazy array, which means that each element of the array is a pointer to another closure. However, the reason you only see 4 bytes per character is because GHC has a static table for Char values < 256, so all the characters end up being shared, and you're left with 4 bytes per char for the pointers, at least when all the array elements are evaluated. Interestingly, a fully evaluated STArray Char takes the same amount of dynamic space as an STUArray Char. It is slower to access, though. Cheers, Simon