[Haskell-cafe] fast Eucl. dist. - Haskell vs C

[Claus Reinke]

>> Once I actually add a 'dist_fast_inline_caller', that indirection  
>> disappears in the inlined code, just as it does for dist_fast itself.
>>
>>    dist_fast_inlined_caller :: UArr Double -> UArr Double -> Bool
>>    dist_fast_inlined_caller p1 p2 = dist_fast_inlined p1 p2 > 2
>>
>> However, in the simpl output for 'dist_fast_inline_caller', the
>> 'sumU' and 'zipWithU' still don't seem to be fused - Don?
> 
> All the 'seq's and so on should be unnecessary, and even so, I still get
> the expected fusion:

As I said, I don't get the fusion if I just add the function above to the 
original Dist.hs, export it and compile the module with '-c -O2 -ddump-simpl':

Dist.dist_fast_inlined_caller =
  \ (w1_s1nb :: Data.Array.Vector.UArr.UArr GHC.Types.Double)
    (w2_s1nc :: Data.Array.Vector.UArr.UArr GHC.Types.Double) ->
    case (Dist.$wzipWithU Dist.lvl2 w1_s1nb w2_s1nc)
         `cast` (trans
                   Data.Array.Vector.UArr.TFCo:R56:UArr
                   Data.Array.Vector.UArr.NTCo:R56:UArr
                 :: Data.Array.Vector.UArr.UArr GHC.Types.Double
                      ~
                    Data.Array.Vector.Prim.BUArr.BUArr GHC.Types.Double)
    of _
    { Data.Array.Vector.Prim.BUArr.BUArr ipv_s1lb
                                         ipv1_s1lc
                                         ipv2_s1ld ->
    letrec {
      $wfold_s1nN :: GHC.Prim.Double#
                     -> GHC.Prim.Int#
                     -> GHC.Prim.Double#
      LclId
      [Arity 2
       Str: DmdType LL]
      $wfold_s1nN =
        \ (ww_s1mZ :: GHC.Prim.Double#) (ww1_s1n3 :: GHC.Prim.Int#) ->
          case GHC.Prim.==# ww1_s1n3 ipv1_s1lc of _ {
            GHC.Bool.False ->
              $wfold_s1nN
                (GHC.Prim.+##
                   ww_s1mZ
                   (GHC.Prim.indexDoubleArray#
                      ipv2_s1ld (GHC.Prim.+# ipv_s1lb ww1_s1n3)))
                (GHC.Prim.+# ww1_s1n3 1);
            GHC.Bool.True -> ww_s1mZ
          }; } in
    case $wfold_s1nN 0.0 0 of ww_s1n7 { __DEFAULT ->
    GHC.Prim.>## (GHC.Prim.sqrtDouble# ww_s1n7) 2.0
    }
    }

Claus