Alternatively, just use "return $! ", which has the same effect as seq-ing, and is generally a good practice (unless you want to be explicitly lazy). See http://johantibell.com/files/haskell-performance-patterns.html. the-thing +RTS -s (with GHC 8) 3,965,758,088 bytes allocated in the heap 46,006,592 bytes copied during GC 207,792 bytes maximum residency (5 sample(s)) <---- down to 200K from 1.5G 182,864 bytes maximum slop 8 MB total memory in use (0 MB lost due to fragmentation) Robin 2017-01-26 12:42 GMT+01:00 Johannes Waldmann < johannes.waldmann@htwk-leipzig.de>:
Thanks for pointing out this (Knuth's) nice test case. I should use this as an exam question ...
Allocation and run-time can be reduced by replacing return (x3' + x4') with let x = (x3' + x4') in x `seq` return x And, modifySTRef' *does* help.
I *do* notice a regression (for the seq-ed and primed version)
ghc-8.0.2 : 2.6 GB alloc, 2.3 sec ghc-6.10.4: 2.0 GB alloc, 1.7 sec
(measured on X5365 @ 3.00GHz )
Numbers are for total allocation, residency is small (it runs with +RTS -H10k -A10k but then the number of GCs goes up)
- J. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.