#10535: Float out causes major space leak -------------------------------------+------------------------------------- Reporter: AlexET | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Description changed by AlexET: Old description:
This issue originally was on haskell-cafe https://mail.haskell.org/pipermail/haskell-cafe/2015-June/120113.html
The following code has a space leak
{{{ #!hs numbers = [1..200]
replicateM' :: Monad m => Int -> m a -> m [a] replicateM' 0 xs = return [] replicateM' n xs = do a <- xs b <- replicateM' (n-1) xs return (a:b)
test :: [[Int]] test = replicateM' 4 numbers
main = print test }}}
The recursive call in replicateM' gets floated out. This then causes a very large (200^3 elements) list to be kept in memory instead of being lazily produced and consumed each time.
A similar thing happens to the replicateM in Control.Monad but it is harder to spot as a lot of specialisation and fusion goes on before the float-out happens
This is similar to #7367 but in this case we have a huge space-leak instead of just adding allocations.
New description: This issue originally was on haskell-cafe https://mail.haskell.org/pipermail/haskell-cafe/2015-June/120113.html The following code has a space leak {{{ #!hs numbers = [1..200] replicateM' :: Monad m => Int -> m a -> m [a] replicateM' 0 xs = return [] replicateM' n xs = do a <- xs b <- replicateM' (n-1) xs return (a:b) test :: [[Int]] test = replicateM' 4 numbers main = print test }}} The recursive call in replicateM' gets floated out. This then causes a very large (200^3^ elements) list to be kept in memory instead of being lazily produced and consumed each time. A similar thing happens to the replicateM in Control.Monad but it is harder to spot as a lot of specialisation and fusion goes on before the float-out happens This is similar to #7367 but in this case we have a huge space-leak instead of just adding allocations. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10535#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler