DiffArray performance unusable for advertized purpose
(cf. this ghc-users thread)
Data.Array.Diff.DiffArray
is unusably slow. Sometimes even Data.Array.Array
is faster in single-threaded use, defeating the purpose. The attached code tries to demonstrate the issue, if I got the single-threadedness via $!
right (default compilation ghc --make SlowDiffArray.hs
gives Array
, build with -DUseDiff
to get DiffArray
).
As I happened to have some older ghcs around, I tried those as well, and it seems the issue got worse around 6.8.3 (SlowDiffArrayA-<version>
: Array; SlowDiffArrayDA-<version>
: DiffArray):
$ for i in *.exe ; do echo $i; time ./$i; done
SlowDiffArrayA-61120081004.exe
9990001
real 0m0.307s
user 0m0.015s
sys 0m0.015s
SlowDiffArrayA-641.exe
9990001
real 0m0.261s
user 0m0.030s
sys 0m0.000s
SlowDiffArrayA-661.exe
9990001
real 0m0.260s
user 0m0.015s
sys 0m0.000s
SlowDiffArrayA-683.exe
9990001
real 0m0.232s
user 0m0.015s
sys 0m0.000s
SlowDiffArrayDA-61120081004.exe
9990001
real 0m12.932s
user 0m0.031s
sys 0m0.000s
SlowDiffArrayDA-641.exe
9990001
real 0m7.114s
user 0m0.015s
sys 0m0.016s
SlowDiffArrayDA-661.exe
9990001
real 0m5.774s
user 0m0.015s
sys 0m0.015s
SlowDiffArrayDA-683.exe
9990001
real 0m12.814s
user 0m0.015s
sys 0m0.000s
(measured on Pentium M 760, 2GHz, Windows XP)
[the majority of the issue probably lies in the DiffArray
implementation, hence component libraries
, but it seems that compiler and runtime system also play a role]
Trac metadata
Trac field | Value |
---|---|
Version | 6.11 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | libraries (other) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |