Generating a tree of various integers results in a space leak

Question

I want to generate a tree containing various integers and find their sum. Here is the code:

{-# LANGUAGE BangPatterns #-}

import Control.Applicative
import Control.Monad.Trans.State

data Tree a = Leaf a | Branch (Tree a) a (Tree a)

new = get <* modify' (+ 1)

tree :: Integer -> Tree Integer
tree n = evalState (go n) 0 where
    go 0 = Leaf <$> new
    go n = Branch <$> go (n - 1) <*> new <*> go (n - 1)

sumTree = go 0 where
    go !a (Leaf n)       = a + n
    go !a (Branch l n r) = go (go (a + n) l) r

main = print $ sumTree (tree 20)

Compiled with -O2, it leads to

     348,785,728 bytes allocated in the heap
     147,227,228 bytes copied during GC
      34,656,860 bytes maximum residency (13 sample(s))
          35,468 bytes maximum slop
              72 MB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0       565 colls,     0 par    0.764s   1.024s     0.0018s    0.0071s
  Gen  1        13 colls,     0 par    0.936s   1.014s     0.0780s    0.3214s

  INIT    time    0.000s  (  0.001s elapsed)
  MUT     time    0.936s  (  0.764s elapsed)
  GC      time    1.700s  (  2.038s elapsed)
  EXIT    time    0.000s  (  0.002s elapsed)
  Total   time    2.636s  (  2.805s elapsed)

  %GC     time      64.5%  (72.7% elapsed)

  Alloc rate    372,631,936 bytes per MUT second

  Productivity  35.5% of total user, 33.4% of total elapsed

Why am I getting this space leak? How to remove it?

Answer 1

, , . , concurrency, , GC .. , , , . :

tree :: Bits b => Int -> Tree b

, .