[erlang-questions] widefinder update

Steve Vinoski <>
Tue Oct 23 23:41:14 CEST 2007


On 10/23/07, Anders Nygren <> wrote:
>
> On 10/23/07, Anders Nygren <> wrote:
> > To summarize my progress on the widefinder problem
> > A few days ago I started with Steve Vinoski's tbray16.erl
> > As a baseline on my 1.66 GHz dual core Centrino
> > laptop, Linux,
> > tbray16
> > real    0m7.067s
> > user    0m12.377s
> > sys     0m0.584s
> >
> > I removed the dict used for the shift table,
> > and changed the min_heap_size.
> > That gave
> > real    0m2.713s
> > user    0m4.168s
> > sys     0m0.412s
> >
> > (see tbray_tuple.erl and wfbm4_tuple.erl)
> > Steve reported that it ran in ~1.9 s on his 8 core server.
> >
> > Then I removed the dicts that were used for collecting the
> > matches and used ets instead, and got some improvement
> > on my dual core laptop.
> > real    0m2.220s
> > user    0m3.252s
> > sys     0m0.344s
> >
> > (see tbray_ets.erl and wfbm4_ets.erl)
> >
> > Interestingly Steve reported that it actually performed
> > worse on his 8 core server.
> >
> > These versions all read the whole file into memory at the start.
> > On my laptop that takes ~400ms (when the file is already cached
> > in the OS).
> >
> > So I changed it to read the file in chucks and spawn the worker
> > after each chunk is read.
> >
> > tbray_blockread with 4 processes
> > real    0m1.992s
> > user    0m3.176s
> > sys     0m0.420s
> >
> > (see tbray_blockread.erl and wfbm4_ets.erl)
> >
> > Running it in the erlang shell it takes ~1.8s.
> >
>
> In the last email I mentioned that
> " Just starting and stopping the VM takes
> time erl -pa ../../bfile/ebin/ -smp -noshell -run init stop
>
> real    0m1.229s
> user    0m0.208s
> sys     0m0.020s"
>
> But I just realized that a more useful measure for basic
> startup and shutdown is
>
> time erl -pa ../../bfile/ebin/ -smp -noshell -run erlang halt
>
> real    0m0.201s
> user    0m0.180s
> sys     0m0.016s


Hmm, good point. On the 8-core:

real    0m0.090s
user    0m0.061s
sys     0m0.012s


--steve
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