I believe `:set +s` displays cpu time, not wall-clock time. On Thu, Mar 5, 2015, at 14:23, David Rush wrote:
Hi all -
Is it my imagination, or are the statistics printed by GHCi when :set +s has been enabled entirely spurious when SMP parallelism is turned on? I'm trying to determine if I am actually getting any improvement, and - both by the wall clock and by the reported statistics I don't seem to be; however, the reported statistics don't seem to line up very well with the wall clock time.
An additional oddity that I've noted is that my algorithm's reference implementation - which simply can't run in parallel due to a foolishly introduced data dependency - still seems to kick 16 CPUs well into the 90%+ utilization range when I have +RTS -N. This code has no parallelism primitives in it whatsoever.
I realize that I'm not being terribly rigorous in my description here, but that is partly because I am not sure how to report on this yet. I think my next step is going to be to build a standalone executable to check using the Unix time command.
For reference I am running Haskell platform from Debian Jessie on a 16- core amd64 system with 29GiB or RAM available. This would appear to be GHC 7.6.3 :(
- d
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe