#8638: Optimize by demoting "denormalized" Integers (i.e. J# -> S#) --------------------------------------------+------------------------------ Reporter: hvr | Owner: hvr Type: feature request | Status: infoneeded Priority: normal | Milestone: 7.8.1 Component: libraries (other) | Version: 7.7 Resolution: | Keywords: integer- Operating System: Unknown/Multiple | gmp Type of failure: Runtime performance bug | Architecture: Test Case: | Unknown/Multiple Blocking: | Difficulty: Unknown | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Comment (by hvr): Replying to [comment:3 simonpj]:
I'd first like to know why `mandel` started allocating nearly 50% more store. (I use `-ticky` for answering this kind of question.) Maybe investigating that will show how the patch can be improved further.
I'm not sure yet why `mandel` allocates more as I couldn't see find any significant use of `Integer`s in the implementation. After some profiling I found out that swapping out the implementation of `magnitude` inside `Mandel.diverge` with a more naive one had a ''huge'' effect on the allocation. Now the report reads: {{{ -------------------------------------------------------------------------------- Program Size Allocs Runtime Elapsed TotalMem -------------------------------------------------------------------------------- ... maillist +0.0% +0.0% 0.04 0.04 +2.2% mandel -0.2% -45.4% 0.02 0.02 +0.0% mandel2 +0.0% +0.0% 0.00 0.00 +0.0% ... -------------------------------------------------------------------------------- Min -0.2% -45.4% -32.3% -32.3% -20.0% Max +0.1% +7.2% +1.6% +1.6% +23.1% Geometric Mean +0.1% -1.3% -1.7% -1.8% +0.0% }}} The modification I made was simply {{{ #!diff diff --git a/spectral/mandel/Mandel.lhs b/spectral/mandel/Mandel.lhs index 3f460ce..cc601f5 100644 --- a/spectral/mandel/Mandel.lhs +++ b/spectral/mandel/Mandel.lhs @@ -109,6 +109,8 @@ is the prelude function that calculates the euclidean norm diverge::Complex Double -> Double -> Bool diverge cmplx radius = magnitude cmplx > radius + where + magnitude (x :+ y) = sqrt (x*x + y*y) \end{code} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8638#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler