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Re: Generate unique ids of maximum length

by rubasov (Friar)
on Apr 13, 2010 at 20:00 UTC ( #834569=note: print w/ replies, xml ) Need Help??

in reply to Generate unique ids of maximum length

Another idea probably worth mentioning: embrace tab completion. Let's suppose we can use tab completion on your input, for instance consider this line:

Lenoc3_duallayer_1 ^^ ^ ^ ^

You must type the marked characters, but the others are optional, they can be completed by pressing tab. Therefore in the shortening process always keep the mandatory characters, but leave out as many optional as needed starting from the right end.

limit shortened 10 Lenoc3_du1 ... 6 Len3d1 5 Le3d1 4 not possible

This is achievable by parsing your input into a suffix tree and operating on that.

L -> XP_ -> 0 -> ... -> 1 -> ... -> enoc -> 3_ -> carina_ -> ... -> duallayer_ -> ... -> 5_ -> carina -> ... -> duallayer -> ...

The first characters of the tree node strings are the mandatory ones, the others are optional. This tree structure seems similar to ikegami's code, however I haven't understood that fully yet, so I'm not sure what's the difference. For me the benefit of this approach seems to be this: you don't need to use the concept of word. Another pro for this algorithm is that you don't need to number your shortened identifiers. (But numbering your input lines (in the base of your input character set) is not bad because that produces the shortest possible unique ids.)

I have some proof of concept code, but take it with a grain of salt: it's unnecessarily complex, employs dirty hacks etc.

use strict; use warnings; use Data::Dump qw( dd ); sub _collapse { my $tree = shift; my ( $stree, $append ); if ( ref $tree ) { my @keys = keys %$tree; if ( @keys == 1 and $keys[0] ne '' ) { ( $stree, $append ) = _collapse( $tree->{ $keys[0] } ); return $stree, defined $append ? $keys[0] . $append : $keys[0]; } else { for (@keys) { ( my $ref, $append ) = _collapse( $tree->{$_} ); $stree->{ defined $append ? $_ . $append : $_ } = $ref; } return $stree; } } return; } sub collapse { my $ctree = shift; my ( $stree, $append ) = _collapse($ctree); if ( defined $append ) { return { $append => $stree }; } else { return $stree; } } sub shorten { my $stree = shift; my $limit = shift; if ( ref $stree ) { while ( my ( $k, $v ) = each %$stree ) { local our @parts = @parts; push @parts, $k if $k ne ''; if ( $k eq '' ) { if ( @parts > $limit ) { print "!\n"; next; } my $remaining = $limit - @parts; my $shortened = ''; for ( 0 .. $#parts ) { $shortened .= substr $parts[$_], 0, 1; my $str = substr $parts[$_], 1, $remaining; $shortened .= $str; last if ( ( $remaining -= length $str ) < 0 ); } print $shortened, "\t", join( '', @parts ), "\n"; } shorten( $v, $limit ); } } } my $ctree = {}; while (<DATA>) { chomp; my $ref = $ctree; for ( split // ) { no warnings 'void'; $ref->{$_}->{''}; # looks like a decent autovivification bug ;-) $ref = $ref->{$_}; } $ref->{''} = undef; } #dd $ctree; my $stree = collapse($ctree); #dd $stree; shorten( $stree => 5 ); __DATA__ A2990_duallayer_1 A2990_duallayer_2 A2990_duallayer_3 A2990_duallayer_4 A2990_duallayer_5 A2990_duallayer_6 A2990_duallayer_7 A2990_duallayer_8 A2990_duallayer_9 A2990_duallayer_10 LXP_01 LXP_02 LXP_03 LXP_04 LXP_05 LXP_06 LXP_07 LXP_08 LXP_09 LXP_10 LXP_11 LXP_12 LXP_13 LXP_14 LXP_15 LXP_16 LXP_17 LXP_18 Normal_1 Normal_2 Normal_3 Normal_4 Normal_5 Normal_6 Lenoc3_carina_A Lenoc3_carina_B Lenoc3_carina_C Lenoc3_duallayer_1 Lenoc3_duallayer_2 Lenoc3_duallayer_3 Lenoc5_carina_1 Lenoc5_carina_2 Lenoc5_carina_3 Lenoc5_duallayer_1 Lenoc5_duallayer_2 Lenoc5_duallayer_3

Some explanation: I've started by parsing the input into a character-level suffix tree. This tree uses hashes, the keys are the substrings, the values are hashrefs of what can follow. A possible ending position of the string is marked by "" => undef. Then collapsed it to a substring-level suffix tree and descended into that to shorten the ids.

Sorry for the late post, yesterday I haven't got enough time to write this.

p.s.: Am I right this is guaranteed to produce unique ids? I'm not sure, but it seems good.

update: answered my own question: Yes, the uniqueness of the shortened ids is guaranteed, no matter what set of optional characters are left out.

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Re^2: Generate unique ids of maximum length
by ikegami (Pope) on Apr 13, 2010 at 20:52 UTC

    This tree structure seems similar to ikegami's code, however I haven't understood that fully yet, so I'm not sure what's the difference.

    My tree is the same as your $ctree:

    A -- ... / \ X -- P -- ... \ / L \ e -- n -- o -- c -- ...

    except numbers are considered atomic in mine.

    I don't bother collapsing into your $stree form:

    A -- ... / \ XP -- ... \ / L \ enoc -- ...

    You must type the marked characters, but the others are optional

    The difference with mine is that I made more character mandatory. The rational is that the OP wanted to the result to resemble the original as much as possible.

    Your mandatory characters:

    • Ambiguous characters.
    Lenoc3_duallayer_1 -> Le3d1 ^^ ^ ^ ^

    My mandatory characters:

    • Ambiguous characters.
    • A sequence of 0+ uppercase letters followed by a sequence of 0+ lowercase letters preceding an ambiguous lowercase letter.
    • First and second unambiguous character of a text sequence
    • Nonletters (digits, underscores)
    Lenoc3_duallayer_1 -> Len3_du_1 ^^^ ^^^^ ^^

      Thanks for the explanation, I've got it. (Then consider my node as an explanation to ikegami's node.)

      It's funny how many different ways people interpret similarity/resemblance, because that was exactly the reason why I chose to keep all the optional characters if the id already fit in the char limit. That way my code always keeps the under-limit ids identical (== more similar). Of course in other cases that's not the optimal choice.

      I also thought of (but not implemented) a more generic way to decide which character to drop from the original id: provide the user a filter callback in which s?he can rate the characters (or substrings) considered, then drop the ones with the lowest rating (still from right to left). For example: [_ ] => 3, [A-Z] => 2, [a-z]=> 1, anything else => 0

      And this is why I've collapsed the char-level suffix tree to the substring-level: to ease the access to substrings for the purpose of rating. And also because the structure of the tree in the substring-level form cannot interfere with the selection of (non-)ambiguous characters (as in choroba's remark above if I get it right).


        And this is why I've collapsed the char-level suffix tree to the substring-level:

        I've always done that too, for exactly the reason you mentioned. I just don't create a tree from the collapsed sequences. I just keep the currently relevant collapsed sequence in a scalar (was called $flux, now called $unsplit).

        I contemplated returning each item as an alternating list of required and optional components (as follows), but I wanted to keep the code a short as possible.

        ( ... [ 'Le', 'noc', '3', '_', 'd', 'uallayer_', '3' ], [ 'Le', 'noc', '5', '_', 'c', 'arina_', '1' ], ... )

        Update: Added last para and accompanying illuatration.

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