package Graph; use utf8; use namespace::autoclean; use Carp; use Moose; use MooseX::SemiAffordanceAccessor; # attribute x is written using set_x($value) and read using x() use List::MoreUtils qw(any); use Node; has 'comments' => (is => 'ro', isa => 'ArrayRef', default => sub {[]}, documentation => 'Sentence-level CoNLL-U comments.'); has 'nodes' => (is => 'ro', isa => 'HashRef', default => sub {my $self = shift; {0 => new Node('id' => 0, 'graph' => $self)}}); #------------------------------------------------------------------------------ # Creates a graph from a list of CoNLL-U lines (the list may or may not contain # the final empty line, it does not matter). This is a static function, it does # not take a reference to a Graph object but it returns one. #------------------------------------------------------------------------------ sub from_conllu_lines { my @sentence = @_; my $graph = new Graph; # Get rid of everything except the node lines. But include empty nodes! foreach my $line (@sentence) { if($line =~ m/^\#/) { push(@{$graph->comments()}, $line); } elsif($line =~ m/^\d/) { my @fields = split(/\t/, $line); my $node = new Node('id' => $fields[0], 'form' => $fields[1], 'lemma' => $fields[2], 'upos' => $fields[3], 'xpos' => $fields[4], '_head' => $fields[6], '_deprel' => $fields[7], '_deps' => $fields[8]); $node->set_feats_from_conllu($fields[5]); $node->set_misc_from_conllu($fields[9]); $graph->add_node($node); } } # Once all nodes have been added to the graph, we can draw edges between them. foreach my $node ($graph->get_nodes()) { $node->set_basic_dep_from_conllu(); $node->set_deps_from_conllu(); } return $graph; } #------------------------------------------------------------------------------ # Generates a list of CoNLL-U lines from the current graph; the list does not # contain the final empty line. #------------------------------------------------------------------------------ sub to_conllu_lines { confess('Incorrect number of arguments') if(scalar(@_) != 1); my $self = shift; my @sentence = @{$self->comments()}; foreach my $node ($self->get_nodes()) { my @fields = ($node->id(), $node->form(), $node->lemma(), $node->upos(), $node->xpos(), $node->get_feats_string(), $node->bparent(), $node->bdeprel(), $node->get_deps_string(), $node->get_misc_string()); push(@sentence, join("\t", @fields)); } return @sentence; } #------------------------------------------------------------------------------ # Checks whether there is a node with the given id. #------------------------------------------------------------------------------ sub has_node { confess('Incorrect number of arguments') if(scalar(@_) != 2); my $self = shift; my $id = shift; confess('Undefined id') if(!defined($id)); return exists($self->nodes()->{$id}); } #------------------------------------------------------------------------------ # Returns node with the given id. If there is no such node, returns undef. #------------------------------------------------------------------------------ sub get_node { confess('Incorrect number of arguments') if(scalar(@_) != 2); my $self = shift; my $id = shift; confess('Undefined id') if(!defined($id)); return $self->has_node($id) ? $self->nodes()->{$id} : undef; } #------------------------------------------------------------------------------ # Returns node with the given id. If there is no such node, returns undef. # This method is just an alias for get_node(). #------------------------------------------------------------------------------ sub node { my $self = shift; my $id = shift; return $self->get_node($id); } #------------------------------------------------------------------------------ # Returns the list of all nodes except the artificial root node with id 0. The # list is ordered by node ids. #------------------------------------------------------------------------------ sub get_nodes { confess('Incorrect number of arguments') if(scalar(@_) != 1); my $self = shift; my @list = map {$self->get_node($_)} (sort { Node::cmpids($a, $b) } (grep {$_ ne '0'} (keys(%{$self->nodes()})))); return @list; } #------------------------------------------------------------------------------ # Adds a node to the graph. The node must have a non-empty id that has not been # used by any other node previously added to the graph. #------------------------------------------------------------------------------ sub add_node { confess('Incorrect number of arguments') if(scalar(@_) != 2); my $self = shift; my $node = shift; my $id = $node->id(); if(!defined($id)) { confess('Cannot add node with undefined ID'); } if($self->has_node($id)) { confess("There is already a node with ID $id in the graph"); } $self->nodes()->{$id} = $node; $node->set_graph($self); } #------------------------------------------------------------------------------ # Removes a node from the graph. Does not change the ids of the remaining # nodes. Returns the Node object that has been disconnected from the graph. # Returns undef if there is no node with the given id. #------------------------------------------------------------------------------ sub remove_node { confess('Incorrect number of arguments') if(scalar(@_) != 2); my $self = shift; my $id = shift; confess('Undefined id') if(!defined($id)); my $node = undef; if($self->has_node($id)) { $node = $self->nodes()->{$id}; delete($self->nodes()->{$id}); $node->set_graph(undef); } return $node; } #------------------------------------------------------------------------------ # Adds an edge between two nodes that are already in the graph. #------------------------------------------------------------------------------ sub add_edge { confess('Incorrect number of arguments') if(scalar(@_) != 4); my $self = shift; my $srcid = shift; my $tgtid = shift; my $deprel = shift; my $srcnode = $self->get_node($srcid); my $tgtnode = $self->get_node($tgtid); confess("Unknown node '$srcid'") if(!defined($srcnode)); confess("Unknown node '$tgtid'") if(!defined($tgtnode)); # Outgoing edge from the source (parent). my %oe = ( 'id' => $tgtid, 'deprel' => $deprel ); # Incoming edge to the target (child). my %ie = ( 'id' => $srcid, 'deprel' => $deprel ); # Check that the same edge does not exist already. push(@{$srcnode->oedges()}, \%oe) unless(any {$_->{id} eq $tgtid && $_->{deprel} eq $deprel} (@{$srcnode->oedges()})); push(@{$tgtnode->iedges()}, \%ie) unless(any {$_->{id} eq $srcid && $_->{deprel} eq $deprel} (@{$tgtnode->iedges()})); } #------------------------------------------------------------------------------ # Removes an existing edge between two nodes of the graph. #------------------------------------------------------------------------------ sub remove_edge { confess('Incorrect number of arguments') if(scalar(@_) != 4); my $self = shift; my $srcid = shift; my $tgtid = shift; my $deprel = shift; my $srcnode = $self->get_node($srcid); my $tgtnode = $self->get_node($tgtid); confess("Unknown node '$srcid'") if(!defined($srcnode)); confess("Unknown node '$tgtid'") if(!defined($tgtnode)); # Outgoing edge from the source (parent). @{$srcnode->oedges()} = grep {!($_->{id} eq $tgtid && $_->{deprel} eq $deprel)} (@{$srcnode->oedges()}); # Incoming edge to the target (child). @{$tgtnode->iedges()} = grep {!($_->{id} eq $srcid && $_->{deprel} eq $deprel)} (@{$tgtnode->iedges()}); } #------------------------------------------------------------------------------ # Graphs refer to nodes and nodes refer back to graphs. We must break this # cycle manually when we are done with the graph, otherwise the Perl garbage # collector will keep the graph and the nodes in the memory forever. Note that # renaming this method to DEMOLISH will not cause Perl to clean up automati- # cally. As long as the references are there, the graph will not be destroyed # and DEMOLISH will not be called. # # Debug memory usage like this (watch the VSZ number): # print STDERR ("Sentence no. $i\n", `ps -p $$ -o vsz,rsz,sz,size`); #------------------------------------------------------------------------------ sub remove_all_nodes { my $self = shift; my @nodes = $self->get_nodes(); foreach my $node (@nodes) { $self->remove_node($node->id()); # We don't have to remove edges manually. They contain node ids but not Perl references. } } __PACKAGE__->meta->make_immutable(); 1; =for Pod::Coverage BUILD =encoding utf-8 =head1 NAME Graph =head1 DESCRIPTION A C holds a list of nodes and can return the C based on its C (the first column in a CoNLL-U file, can be integer or a decimal number). Edges are stored in nodes. It is currently necessary to call the method C when the graph is no longer needed. Otherwise cyclic references will prevent Perl from freeing the memory occupied by the graph and its nodes. =head1 ATTRIBUTES =over =item comments A read-only attribute (filled during construction) that holds the sentence-level comments from the CoNLL-U file. =item nodes A hash (reference) that holds the individual L objects, indexed by their ids from the first column of the CoNLL-U file. =back =head1 METHODS =over =item $graph = Graph::from_conllu_lines (@sentence); Creates a graph from a list of CoNLL-U lines (the list may or may not contain the final empty line, it does not matter). This is a static function, it does not take a reference to a Graph object but it returns one. =item @sentence = $graph->to_conllu_lines (); Generates a list of CoNLL-U lines from the current graph; the list does not contain the final empty line. =item $graph->has_node ($id); Returns a nonzero value if there is a node with the given id in the graph. =item $graph->get_node ($id); =item $graph->node ($id); Returns the object with the node with the given id. =item @nodes = $graph->get_nodes (); Returns the list of all nodes except the artificial root node with id 0. The list is ordered by node ids. =item $graph->add_node ($node); Adds a node (a L object) to the graph. The node must have a non-empty id that has not been used by any other node previously added to the graph. =item $graph->remove_node ($id); Removes a node from the graph. Does not change the ids of the remaining nodes. Returns the L object that has been disconnected from the graph. Returns undef if there is no node with the given id. =item $graph->add_edge ($source_id, $target_id, $relation_label); Adds an edge between two nodes that are already in the graph. =item $graph->remove_edge ($source_id, $target_id, $relation_label); Removes an existing edge between two nodes of the graph. =item $graph->remove_all_nodes (); Currently the only way of breaking cyclic references when the graph is no longer needed. Make sure to call this method in order to prevent memory leaks! =back =head1 AUTHORS Daniel Zeman =head1 COPYRIGHT AND LICENSE Copyright © 2019, 2020 by Institute of Formal and Applied Linguistics, Charles University in Prague This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.