On 11 Jan 2008, at 2:20 PM, Andre Nathan wrote:
On Fri, 2008-01-11 at 13:27 -0200, Andre Nathan wrote:
I was wondering if laziness would make it run as if it was a
single O(n)
operation (get one directory entry "on demand", pass it to filter and
then to insertInTree), because only one entry is used at a time,
so that
only the "current" entry needs to be evaluated.
I did some experiments. This for 1000 reads of the entries of a
directory with 10000 entries, checking if they match ^[0-9]+$ and
printing those which do (half of them).
getDirectoryEntries, filter, mapM_:
65.52s user 6.01s system 87% cpu 1:22.21 total
openDirStream, readDirStream:
39.68s user 5.69s system 95% cpu 47.746 total
getDirectoryContents, mapM_:
63.40s user 5.96s system 95% cpu 1:12.70 total
These are all known and expected. As I said, you can expect lazy
versions to normally be slower than explicit loops. The question is
whether 50% more time and 300% more memory has a higher cost in your
case than the extra complexity and reduced modularity of the lazy code.
jcc
_______________________________________________
Haskell-Cafe mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/haskell-cafe
