Performance regression on typechecking type families?

Dr. ERDI Gergo gergo at
Sat Nov 29 10:17:30 UTC 2014


Prompted by this question:
I wrote some code today using closed type families and datakinds. Also, as 
a baseline, I typechecked the code using open type families from 
the original question.

The two files are here:

On GHC 7.8.3, typechecking took about 45 seconds for each. However, on a 
'perf' build of GHC 7.9 d8c437b3, with ghc-stage2, the first one took 1m3s 
and the second one 1m12s. A 40% and 60% increase in typechecking time, 

Is this some known regression, something surprising, or is 'perf' simply 
not the right build flavour for this kind of comparison?


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