Beefy Boxes and Bandwidth Generously Provided by pair Networks
Think about Loose Coupling
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??
After some thought I realized that I could find several speedups. The first and biggest is what order the toggles are searched in. When you choose elements on one side, you can conclude diagonally. But I have to fill in the entire board before drawing interesting conclusions. Therefore by just reording what path you take you move the decision closer to the conclusion and speed things up.

The other thing that I changed is that I separated the decision about what paths to take from the toggling. As it stands for most of the board the decision is obvious from examining one board element what you have to do. But I was toggling twice whether or not I needed it. But by separating out that logic I make the logical structure simpler, and I believe it is slightly faster.

So here is a much speeded up version of the code:

use strict; use vars qw($min $max @board @soln @toggles); $min = 1; $max = shift(@ARGV) || 5; @board = map [map 0, $min..$max], $min..$max; foreach my $x ($min..$max) { foreach my $y ($min..$max) { push @toggles, [ [$x, $y], ret_valid_toggles($x, $y), ret_toggle_square($x, $y) ]; } } # Sort them in an order where conclusions are discovered faster @toggles = sort { ($a->[0][0] + $a->[0][1]) <=> ($b->[0][0] + $b->[0][1]) or $a->[0][0] <=> $b->[0][0] } @toggles; find_soln(); sub find_soln { if (! @toggles) { # Solved! print join " ", "Solution:", map "$_->[0][0]-$_->[0][1]", @soln; print "\n"; } else { my $toggle = shift(@toggles); foreach ($toggle->[1]->()) { if ($_) { $toggle->[2]->(); push @soln, $toggle; find_soln(); pop @soln; $toggle->[2]->(); } else { find_soln(); } } unshift @toggles, $toggle; } } # Returns a function that toggles one square and its # neighbours. sub ret_toggle_square { my ($x, $y) = @_; my @to_swap= square_ref($x, $y); unless ($x == $min) { push @to_swap, square_ref($x - 1, $y); } unless ($y == $min) { push @to_swap, square_ref($x, $y - 1); } unless ($x == $max) { push @to_swap, square_ref($x + 1, $y); } unless ($y == $max) { push @to_swap, square_ref($x, $y + 1); } return sub { $$_ = not $$_ foreach @to_swap; }; } # Returns a test functions that returns a list of valid # toggle states to try sub ret_valid_toggles { my ($x, $y) = @_; my @checks; if ($min < $x) { push @checks, square_ref($x-1, $y); } if ($max == $x) { if ($min < $y) { push @checks, square_ref($x, $y-1); } if ($max == $y) { push @checks, square_ref($x, $y); } } if (not @checks) { return sub {(0, 1)}; } else { my $check = shift @checks; if (not @checks) { return sub {not $$check}; } else { return sub { my $val = $$check; (grep {$$_ != $val} @checks) ? () : not $val; }; } } } # Given x, y returns a reference to that square on the board sub square_ref { my ($x, $y) = @_; return \($board[$x-1][$y-1]); }

UPDATE
Removed the ret_swap_square() function. Toggles go much faster if each swap is done directly rather than indirectly through a function call. (Removing 5 extra function calls per toggle matters...) Also dropped the unused Carp that snuck in through habit. (This is throw-away code...)


In reply to Re (tilly) 2: 5x5 Puzzle by tilly
in thread 5x5 Puzzle by Adam

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others scrutinizing the Monastery: (3)
As of 2024-06-19 00:24 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found

    Notices?
    erzuuli‥ 🛈The London Perl and Raku Workshop takes place on 26th Oct 2024. If your company depends on Perl, please consider sponsoring and/or attending.