GHC 8.4.1-rc1 is slower on a ray-tracer project

Ben Gamari ben at
Wed Feb 28 19:22:06 UTC 2018

David Feuer <david.feuer at> writes:

> I don't see how 62 seconds rather than 60 is anything close to going off
> the rails. Did I read something wrong? This sounds more like a minor wibble.
"Off the rails" was a rhetorical flourish; indeed a single program
regressing by 3% isn't a catastrophe.

That being said, runtime performance improvements are hard-won prizes.
Consider that the largest allocations improvement arising from the
"Compiling without Continuations" paper was ~8%. Consequently, if
someone comes along with a 3% regression we would remiss not to
take it seriously.


- Ben

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