[Haskell-cafe] GHC 7.0.1 developer challenges

[John D. Ramsdell]

On Thu, Dec 16, 2010 at 4:13 AM, Simon Marlow <marlowsd at gmail.com> wrote:
>
> If your program has large memory requirements, you might also benefit from
> parallel GC in the old generation: +RTS -N2 -qg1.l

Testing shows this advice did not help in my case.  The program that
implements the undecidable algorithm in my package is already
multiprocessor aware, but there is an inheritly sequential support
program that translates the output of the main program into an XHTML
document.  For reasons I shall spare you of, this program is also
memory intensive, sometimes requiring more memory that the main
program.  When this program is compiled without the -threaded option,
and run on a large input, I found the program used 85 seconds of user
time, and 99% of the CPU time on a Core 2 Duo machine.  After
compiling with the -threaded option, and running with -N2 -qg1, the
program used 88 seconds of user time, and 103% of the CPU.  I ran the
test on what is provided by the Ubuntu package system for Ubuntu Lucid
Lynx, GHC 6.12.1 and parallel 1.1.0.1.

John