Hello, this is my first posting to this List, I hope everything goes well. Seeing that the haskell is currently poorly represented in the fasta benchmark at http://shootout.alioth.debian.org/u64q/benchmark.php?test=fasta&lang=all , I decided to help out the contributors a bit. My draft already performs considerably better than the current program, but while optimizing I ran into a weird problem. I already reported this as a ghc bug, but on IRC I was encouraged to also describe my problem here. Source of the program: http://rohanlean.de/pub/ghc_alloc/fasta.hs Core: http://rohanlean.de/pub/ghc_alloc/fasta.core Relevant port of the core (`gen' with inlined `pick'): http://rohanlean.de/pub/ghc_alloc/fasta_snip.core Running with the -p option suggested that `gen' and `pick' allocate a lot of memory throughout the run of the program (that memory is not retained). I managed to confirm that for non-profiling builds by observing how the the output of -sstderr changed when I modified `gen' to call itself fewer times. This came as a surprise, because expected these two functions to be completely allocation free, and the core does not suggest any allocation to me. I would very much welcome explanations for these reported allocations. Thank you, Rohan Lean