[GHC] #15143: Passing an IO value through several functions results in program hanging.

[GHC]

#15143: Passing an IO value through several functions results in program hanging.
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        Reporter:  Burtannia         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by osa1):

 I made the slow program parametric on number of iterations. Seems like an
 exponential behavior in the generated code:

 {{{
 $ for n ({20..30}); do time ./Slow $n; done
 ObsTemp 1
 ./Slow $n  0,05s user 0,00s system 85% cpu 0,064 total
 ObsTemp 1
 ./Slow $n  0,08s user 0,00s system 91% cpu 0,092 total
 ObsTemp 1
 ./Slow $n  0,16s user 0,00s system 98% cpu 0,162 total
 ObsTemp 1
 ./Slow $n  0,31s user 0,00s system 99% cpu 0,312 total
 ObsTemp 1
 ./Slow $n  0,62s user 0,00s system 99% cpu 0,622 total
 ObsTemp 1
 ./Slow $n  1,23s user 0,00s system 99% cpu 1,242 total
 ObsTemp 1
 ./Slow $n  2,47s user 0,00s system 99% cpu 2,472 total
 ObsTemp 1
 ./Slow $n  5,11s user 0,00s system 99% cpu 5,112 total
 ObsTemp 1
 ./Slow $n  9,85s user 0,00s system 99% cpu 9,862 total
 ObsTemp 1
 ./Slow $n  19,92s user 0,01s system 100% cpu 19,922 total
 ^C^C
 }}}

 Increasing the iteration count by one causes time it takes to double.5

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15143#comment:4>
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