[erlang-questions 37] Re: A sudoku solver in Erlang compared to Python

Ahmed Omar <>
Sat Mar 26 21:33:40 CET 2011


actually instead of doing

    NonUniquePeers = shallow_flatten([S || S <- units(Square)]),
    PeerSet = sets:from_list(NonUniquePeers),
    PeersWithSelf = sets:to_list(PeerSet),

can't u just do
PeersWithSelf = lists:usort(NonUniquePeers).
?


On Sat, Mar 26, 2011 at 9:14 PM, Evans, Matthew <> wrote:

> Good call....gb_sets should be faster. Compiled to native it runs faster
> still
>
> 9> sudoku:print_results("top95.txt", "\n").
> Solved 95 of 95 puzzles from top95.txt in 0.810156 secs (117.26 Hz)
> (901201 total eliminations, avg 9486.33, median 6267, max 56820, min 1792).
> ok
>
> ________________________________________
> From: Ahmed Omar []
> Sent: Saturday, March 26, 2011 3:08 PM
> To: Andreas Pauley
> Cc: Evans, Matthew; 
> Subject: Re: [erlang-questions 20] Re: A sudoku solver in Erlang compared
> to Python
>
> using gb_sets instead of sets could decrease eliminations a bit and give u
> some boost. However, i didn't dive deeper into the code or the algorithm.
>
> On Sat, Mar 26, 2011 at 9:41 AM, Andreas Pauley <<mailto:
> >> wrote:
> Thanks, I've changed the compile options and this definitely makes it
> somewhat faster:
>
> https://github.com/apauley/sudoku-in-erlang/commit/b7ce2abb6ca013850ed8f3e8fd7f5f6be7004cbb
>
> Strangely the native flag is not documented here:
> http://www.erlang.org/doc/man/compile.html#file-2
>
> The more interesting improvement would be to decrease the number of
> eliminations performed, but for that I'll have to go deep into the
> code :-)
>
>
> On Sat, Mar 26, 2011 at 12:16 AM, Evans, Matthew <
> <mailto:>> wrote:
> > Without going deep into the code, one thing to try is compile with the
> native flag (running the tests from the VM shell here):
> >
> > Without native set:
> > 18> c(sudoku).
> > {ok,sudoku}
> > 19>  sudoku:print_results("top95.txt", "\n").
> > Solved 95 of 95 puzzles from top95.txt in 2.038825 secs (46.60 Hz)
> > (922678 total eliminations, avg 9712.40, median 6596, max 55370, min
> 1797).
> > ok
> >
> >
> > With native set:
> > 20> c(sudoku,[native]).
> > {ok,sudoku}
> > 21>  sudoku:print_results("top95.txt", "\n").
> > Solved 95 of 95 puzzles from top95.txt in 1.613416 secs (58.88 Hz)
> > (922678 total eliminations, avg 9712.40, median 6596, max 55370, min
> 1797).
> >
> >
> >
> > -----Original Message-----
> > From: <mailto:
> > [mailto:
> <mailto:
> >] On Behalf Of Andreas Pauley
> > Sent: Friday, March 25, 2011 8:15 AM
> > To: <mailto:>
> > Subject: [erlang-questions 4] A sudoku solver in Erlang compared to
> Python
> >
> > Hi all,
> >
> > In my quest to learn Erlang I've translated Peter Norvig's sudoku
> > solver into Erlang:
> > https://github.com/apauley/sudoku-in-erlang
> >
> > For comparison, my slightly modified version of Norvig's Python code
> > can be found here:
> > https://github.com/apauley/sudoku-by-norvig
> >
> > I like the pattern matching, it was fun to do the entire solution
> > without a single if or case statement :-)
> > Something that bothers me though is that the Python solution seems to
> > be faster, even after I've made the Erlang solution use multiple
> > processors.
> >
> > In order to compare the two solutions I counted the number of
> > eliminations each performed.
> > The eliminate function is the core of the solution, for example
> > assigning a single value to a square is implemented as the elimination
> > of all other values.
> >
> > With the Erlang implementation I get:
> > sudoku-in-erlang$ ./sudoku
> > All tests passed :-)
> > Solved 50 of 50 puzzles from easy50.txt in 2.890978 secs (17.30 Hz)
> >  (93403 total eliminations, avg 1868.06, median 1810, max 2517, min
> 1770).
> > Solved 95 of 95 puzzles from top95.txt in 22.004369 secs (4.32 Hz)
> >  (922678 total eliminations, avg 9712.40, median 6596, max 55370, min
> 1797).
> > Solved 11 of 11 puzzles from hardest.txt in 0.851678 secs (12.92 Hz)
> >  (32339 total eliminations, avg 2939.91, median 2894, max 4779, min
> 1781).
> >
> > And with the Python implementation:
> > sudoku-by-norvig$ ./sudoku.py
> > All tests pass.
> > Solved 50 of 50 puzzles from easy50.txt in 0.792008 secs (63.13 Hz)
> >  (33059 total eliminations, avg 661.00, median 648, max 830, min 648).
> > Solved 95 of 95 puzzles from top95.txt in 5.903875 secs (16.09 Hz)
> >  (221997 total eliminations, avg 2336.00, median 1492, max 11512, min
> 648).
> > Solved 11 of 11 puzzles from hardest.txt in 0.237532 secs (46.31 Hz)
> >  (9436 total eliminations, avg 857.00, median 817, max 1198, min 648).
> >
> > So according to the stats above, the Python solution performs less
> > computations when given exactly the same input.
> > The Erlang code is as close to the Python as I could make it, I've
> > done more or less a direct translation of the algorithms used.
> >
> > I suspect that there are some lazy evaluation happening in the Python
> > version, possibly generators, although I haven't pinpointed it yet.
> >
> > How can I improve my Erlang code in this solution?
> >
> > Kind regards,
> > Andreas
> > _______________________________________________
> > erlang-questions mailing list
> > <mailto:>
> > http://erlang.org/mailman/listinfo/erlang-questions
> >
> _______________________________________________
> erlang-questions mailing list
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>
>
> --
> Best Regards,
> - Ahmed Omar
> http://nl.linkedin.com/in/adiaa
> Follow me on twitter
> @spawn_think<http://twitter.com/#!/spawn_think>
>
>


-- 
Best Regards,
- Ahmed Omar
http://nl.linkedin.com/in/adiaa
Follow me on twitter
@spawn_think <http://twitter.com/#!/spawn_think>
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