Normal: real 3m14.295s user 3m9.879s sys 0m2.143s

All-In-One: real 1m11.380s user 0m10.102s sys 0m1.711s

Something very odd is going on. GHC does not generate programs than run 3x faster between GHC versions.

This comparison is actually between an nhc98-built program (the first one) and a ghc-built program (the second one), showing that (in this specific case) nhc98 is generating code that is three times slower than that generated by ghc. In my experience, a speed difference of between 2x and 5x of the (unoptimised) generated code between the two compilers is fairly typical. The really odd thing is in the second set of figures. Unless there has been a cut-n-paste mistake, the user+system times do not add up even close to the wall-clock time, suggesting a much greater difference of 18x, which would start to worry me a little if it were true. However, Hal posted an updated set of figures comparing a program separately compiled with ghc to all-in-one compiled with ghc, and these figures seem to have a similar same user+system /= real discrepancy:

separately compiled with ghc: real 0m27.167s user 0m9.991s sys 0m1.304s

all-in-one compiled with ghc: real 0m31.411s user 0m10.007s sys 0m1.299s

Is this some kind of known Cygwin timing problem? Do ghc executables fiddle with the internal timers at runtime? :-) Regards, Malcolm