ExonScoreBuilder.pm

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=head1 LICENSE
 
Copyright [1999-2015] Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute
Copyright [2016-2024] EMBL-European Bioinformatics Institute
 
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 
     http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 
=cut
 
 
=head1 CONTACT
 
  Please email comments or questions to the public Ensembl
  developers list at <http://lists.ensembl.org/mailman/listinfo/dev>.
 
  Questions may also be sent to the Ensembl help desk at
  <http://www.ensembl.org/Help/Contact>.
 
=cut
 
=head1 NAME
 
=head1 SYNOPSIS
 
=head1 DESCRIPTION
 
Combines ExonScoreBuilder, ExonDirectMapper and ExonerateRunner from
Java application.
 
=head1 METHODS
 
=cut
 
package Bio::EnsEMBL::IdMapping::ExonScoreBuilder;
 
use strict;
use warnings;
no warnings 'uninitialized';
 
use Bio::EnsEMBL::IdMapping::ScoreBuilder;
our @ISA = qw(Bio::EnsEMBL::IdMapping::ScoreBuilder);
 
use Bio::EnsEMBL::Utils::Argument qw(rearrange);
use Bio::EnsEMBL::Utils::Exception qw(throw warning);
use Bio::EnsEMBL::Utils::ScriptUtils qw(parse_bytes path_append);
use Bio::EnsEMBL::IdMapping::ScoredMappingMatrix;
 
 
#
# exon scoring is done in two steps:
# 1. map exons by overlap (if a common coord_system exists)
# 2. map remaining and poorly scoring exons using exonerate
#
sub score_exons {
  my $self = shift;
 
  $self->logger->info( "-- Scoring exons...\n\n", 0, 'stamped' );
 
  # score using overlaps, then exonerate
  my $matrix = $self->overlap_score;
 
  my $exonerate_matrix = $self->exonerate_score($matrix);
 
  # log stats before matrix merging
  $self->logger->info("\nOverlap scoring matrix:\n");
  $self->log_matrix_stats($matrix);
  $self->logger->info("\nExonerate scoring matrix:\n");
  $self->log_matrix_stats($exonerate_matrix);
 
  # merge matrices
  $self->logger->info( "\nMerging scoring matrices...\n", 0,
                       'stamped' );
  $matrix->merge($exonerate_matrix);
 
  $self->logger->info( "Done.\n\n", 0, 'stamped' );
 
  # debug logging
  if ( $self->logger->loglevel eq 'debug' ) {
    $matrix->log( 'exon', $self->conf->param('basedir') );
  }
 
  # log stats of combined matrix
  $self->logger->info("Combined scoring matrix:\n");
  $self->log_matrix_stats($matrix);
 
  $self->logger->info( "\nDone with exon scoring.\n\n", 0, 'stamped' );
 
  return $matrix;
} ## end sub score_exons
 
 
#
# direct mapping by overlap (if common coord_system exists)
#
sub overlap_score {
  my $self = shift;
 
  my $dump_path =
    path_append( $self->conf->param('basedir'), 'matrix' );
 
  my $matrix =
    Bio::EnsEMBL::IdMapping::ScoredMappingMatrix->new(
                               -DUMP_PATH  => $dump_path,
                               -CACHE_FILE => 'exon_overlap_matrix.ser',
    );
 
  my $overlap_cache = $matrix->cache_file;
 
  if ( -s $overlap_cache ) {
 
    # read from file
    $self->logger->info(
                   "Reading exon overlap scoring matrix from file...\n",
                   0, 'stamped' );
    $self->logger->debug( "Cache file $overlap_cache.\n", 1 );
    $matrix->read_from_file;
    $self->logger->info( "Done.\n", 0, 'stamped' );
 
  }
  else {
 
    # build scoring matrix
    $self->logger->info(
         "No exon overlap scoring matrix found. Will build new one.\n");
 
    if ( $self->cache->highest_common_cs ) {
      $self->logger->info( "Overlap scoring...\n", 0, 'stamped' );
      $matrix = $self->build_overlap_scores($matrix);
      $self->logger->info( "Done.\n", 0, 'stamped' );
    }
 
    # write scoring matrix to file
    $matrix->write_to_file;
 
  }
 
  return $matrix;
} ## end sub overlap_score
 
 
#
# map the remaining exons using exonerate
#
sub exonerate_score {
  my $self   = shift;
  my $matrix = shift;
 
  unless ( $matrix and
          $matrix->isa('Bio::EnsEMBL::IdMapping::ScoredMappingMatrix') )
  {
    throw('Need a Bio::EnsEMBL::IdMapping::ScoredMappingMatrix.');
  }
 
  my $dump_path =
    path_append( $self->conf->param('basedir'), 'matrix' );
 
  my $exonerate_matrix =
    Bio::EnsEMBL::IdMapping::ScoredMappingMatrix->new(
                             -DUMP_PATH  => $dump_path,
                             -CACHE_FILE => 'exon_exonerate_matrix.ser',
    );
 
  my $exonerate_cache = $exonerate_matrix->cache_file;
 
  if ( -s $exonerate_cache ) {
 
    # read from file
    $self->logger->info( "Reading exonerate matrix from file...\n",
                         0, 'stamped' );
    $self->logger->debug( "Cache file $exonerate_cache.\n", 1 );
    $exonerate_matrix->read_from_file;
    $self->logger->info( "Done.\n", 0, 'stamped' );
 
  }
  else {
 
    # build scoring matrix
    $self->logger->info(
                    "No exonerate matrix found. Will build new one.\n");
 
    # dump exons to fasta files
    my $dump_count = $self->dump_filtered_exons($matrix);
 
    if ($dump_count) {
      # run exonerate
      $self->run_exonerate;
 
      # parse results
      $self->parse_exonerate_results($exonerate_matrix);
 
    }
    else {
 
      $self->logger->info( "No source and/or target exons dumped, " .
                           "so don't need to run exonerate.\n" );
 
    }
 
    # write scoring matrix to file
    $exonerate_matrix->write_to_file;
 
  } ## end else [ if ( -s $exonerate_cache)]
 
  return $exonerate_matrix;
} ## end sub exonerate_score
 
#
# Algorithm:
# Get a lists of exon containers for source and target.  Walk along both
# lists, set a flag when you first encounter an exon (i.e. it starts).
# Record all alternative exons until you encounter the exon again (exon
# ends), then score against all alternative exons you've recorded.
#
sub build_overlap_scores {
  my ( $self, $matrix ) = @_;
 
  unless ($matrix
      and $matrix->isa('Bio::EnsEMBL::IdMapping::ScoredMappingMatrix') )
  {
    throw('Need a Bio::EnsEMBL::IdMapping::ScoredMappingMatrix.');
  }
 
  # get sorted list of exon containers
  $self->logger->info( "Reading sorted exons from cache...\n",
                       1, 'stamped' );
 
  my @source_exons =
    $self->sort_exons( [
        values %{ $self->cache->get_by_name( 'exons_by_id', 'source' ) }
      ] );
 
  my @target_exons =
    $self->sort_exons( [
        values %{ $self->cache->get_by_name( 'exons_by_id', 'target' ) }
      ] );
 
  $self->logger->info( "Done.\n", 1, 'stamped' );
 
  # get first source and target exon container
  my $source_ec = shift(@source_exons);
  my $target_ec = shift(@target_exons);
 
  my %source_overlap = ();
  my %target_overlap = ();
 
  $self->logger->info( "Scoring...\n", 1, 'stamped' );
 
  while ( defined($source_ec) || defined($target_ec) ) {
    my $add_source = 0;
    my $add_target = 0;
 
    # compare exon containers
    if ( defined($source_ec) && defined($target_ec) ) {
      my $cmp =
        $self->compare_exon_containers( $source_ec, $target_ec );
      if ( $cmp <= 0 ) { $add_source = 1 }
      if ( $cmp >= 0 ) { $add_target = 1 }
    }
    elsif ( defined($source_ec) ) {
      $add_source = 1;
    }
    elsif ( defined($target_ec) ) {
      $add_target = 1;
    }
    else {
      die('The world is a strange place');
    }
 
    if ($add_source) {
      if ( exists( $source_overlap{ $source_ec->[0] } ) ) {
        # remove exon from list of overlapping source exons to score
        # target against
        delete $source_overlap{ $source_ec->[0] };
      }
      else {
        # add exon to list of overlapping source exons to score target
        # against
        $source_overlap{ $source_ec->[0] } = $source_ec->[0];
 
        # score source exon against all target exons in current overlap
        # list
        foreach my $target_exon ( values %target_overlap ) {
          if ( defined( $matrix->get_score(
                                   $source_ec->[0]->id, $target_exon->id
                        ) ) )
          {
            next;
          }
 
          $self->calc_overlap_score( $source_ec->[0], $target_exon,
                                     $matrix );
        }
      }
 
      # get next source exon container
      $source_ec = shift(@source_exons);
    } ## end if ($add_source)
 
    if ($add_target) {
      if ( exists( $target_overlap{ $target_ec->[0] } ) ) {
        # remove exon from list of overlapping target exons to score
        # source against
        delete $target_overlap{ $target_ec->[0] };
      }
      else {
        # add exon to list of overlapping target exons to score source
        # against
        $target_overlap{ $target_ec->[0] } = $target_ec->[0];
 
        # score target exon against all source exons in current overlap
        # list
        foreach my $source_exon ( values %source_overlap ) {
          if ( defined( $matrix->get_score(
                                   $source_exon->id, $target_ec->[0]->id
                        ) ) )
          {
            next;
          }
 
          $self->calc_overlap_score( $source_exon, $target_ec->[0],
                                     $matrix );
        }
      }
 
      # get next target exon container
      $target_ec = shift(@target_exons);
    } ## end if ($add_target)
  } ## end while ( defined($source_ec...))
 
  $self->logger->info( "Done.\n", 1, 'stamped' );
 
  return $matrix;
} ## end sub build_overlap_scores
 
 
#
# Return a list of exon containers, sorted by seq_region_name, then location
# (where location is either start-1 or end, so each exon is in the list twice).
# An exon container is a listrefs of a TinyExon object and its location. This
# implements the ExonSortContainer in the java application.
#
sub sort_exons {
  my $self  = shift;
  my $exons = shift;
 
  ## no critic 
  return sort {
    ( $a->[0]->common_sr_name cmp $b->[0]->common_sr_name ) ||
      ( $a->[1] <=> $b->[1] )
    } ( map { [ $_, $_->common_start - 1 ] } @$exons ),
    ( map { [ $_, $_->common_end ] } @$exons );
}
 
sub compare_exon_containers {
  my $self = shift;
  my $e1   = shift;
  my $e2   = shift;
 
  return ( ( $e1->[0]->common_sr_name cmp $e2->[0]->common_sr_name ) ||
           ( $e1->[1] <=> $e2->[1] ) );
}
 
#
# Calculates overlap score between two exons. Its done by dividing
# overlap region by exons sizes. 1.0 is full overlap on both exons.
# Score of at least 0.5 are added to the exon scoring matrix.
#
sub calc_overlap_score {
  my $self        = shift;
  my $source_exon = shift;
  my $target_exon = shift;
  my $matrix      = shift;
 
  my ( $start, $end );
 
  # don't score if exons on different strand
  return unless ( $source_exon->strand == $target_exon->strand );
 
  # determine overlap start
  if ( $source_exon->start > $target_exon->start ) {
    $start = $source_exon->start;
  }
  else {
    $start = $target_exon->start;
  }
 
  # determine overlap end
  if ( $source_exon->end < $target_exon->end ) {
    $end = $source_exon->end;
  }
  else {
    $end = $target_exon->end;
  }
 
  #
  # Calculate score, which is defined as average overlap / exon length
  # ratio.
  #
 
  my $overlap       = $end - $start + 1;
  my $source_length = $source_exon->end - $source_exon->start + 1;
  my $target_length = $target_exon->end - $target_exon->start + 1;
 
  my $score = ( $overlap/$source_length + $overlap/$target_length )/2;
 
  # The following penalty was removed because it meant that an exon
  # whose sequence and position had not changed would become a
  # candidate for similarity mapping when its phase changed.  This
  # caused lots of criss-crossing stable ID history entries between
  # genes/transcripts/translations in some gene families.
  #
  ## PENALTY:
  ## penalise by 10% if phase if different
  if ( $source_exon->phase != $target_exon->phase ) {
    $score *= 0.9;
  }
 
  # add score to scoring matrix if it's at least 0.5
  if ( $score >= 0.5 ) {
    $matrix->add_score( $source_exon->id, $target_exon->id, $score );
  }
 
} ## end sub calc_overlap_score
 
 
sub run_exonerate {
  my $self = shift;
 
  my $source_file = $self->exon_fasta_file('source');
  my $target_file = $self->exon_fasta_file('target');
  my $source_size = -s $source_file;
  my $target_size = -s $target_file;
 
  # check if fasta files exist and are not empty
  unless ($source_size and $target_size) {
    throw("Can't find exon fasta files.");
  }
 
  # create an empty lsf log directory
  my $logpath = path_append($self->logger->logpath, 'exonerate');
  system("rm -rf $logpath") == 0 or
    $self->logger->error("Unable to delete lsf log dir $logpath: $!\n");
  system("mkdir -p $logpath") == 0 or
    $self->logger->error("Can't create lsf log dir $logpath: $!\n");
 
  # delete exonerate output from previous runs
  my $dump_path = $self->cache->dump_path;
 
  opendir(my $dumpdir, $dump_path) or
    $self->logger->error("Can't open $dump_path for reading: $!");
 
  while (defined(my $file = readdir($dumpdir))) {
    next unless /exonerate_map\.\d+/;
 
    unlink("$dump_path/$file") or
      $self->logger->error("Can't delete $dump_path/$file: $!");
  }
  
  closedir($dumpdir);
 
  # determine number of jobs to split task into
  my $bytes_per_job = $self->conf->param('exonerate_bytes_per_job')
    || 250000;
  my $num_jobs = $self->conf->param('exonerate_jobs');
  $num_jobs ||= int( $source_size/$bytes_per_job + 1 );
 
  my $percent =
    int( ( $self->conf->param('exonerate_threshold') || 0.5 )*100 );
  my $lsf_name       = 'idmapping_exonerate_' . time;
  my $exonerate_path = $self->conf->param('exonerate_path');
  my $exonerate_extra_params =
    $self->conf->param('exonerate_extra_params');
 
  #
  # run exonerate jobs using lsf
  #
  my $exonerate_job =
    qq{$exonerate_path } .
    qq{--query $source_file --target $target_file } .
    q{--querychunkid $LSB_JOBINDEX } .
    qq{--querychunktotal $num_jobs } .
    q{--model ungapped -M 1000 -D 100 } .
    q{--showalignment FALSE --subopt no } . qq{--percent $percent } .
    $self->conf->param('exonerate_extra_params') . " " .
    q{--ryo 'myinfo: %qi %ti %et %ql %tl\n' } .
    qq{| grep '^myinfo:' > $dump_path/exonerate_map.\$LSB_JOBINDEX} .
    "\n";
 
  $self->logger->info("Submitting $num_jobs exonerate jobs to lsf.\n");
  $self->logger->debug("$exonerate_job\n\n");
 
  my $bsub_cmd = sprintf(
               "|bsub -J '%s[1-%d]%%%d' -o %s/exonerate.%%I.out %s",
               $lsf_name,
               $num_jobs,
               $self->conf()->param('exonerate_concurrent_jobs') || 200,
               $logpath,
               $self->conf()->param('lsf_opt_exonerate') );
 
  local *BSUB;
  open( BSUB, $bsub_cmd ) ## no critic
    or $self->logger->error("Could not open open pipe to bsub: $!\n");
 
  print BSUB $exonerate_job;
  $self->logger->error("Error submitting exonerate jobs: $!\n")
    unless ($? == 0); 
  close BSUB;
 
  # submit dependent job to monitor finishing of exonerate jobs
  $self->logger->info("Waiting for exonerate jobs to finish...\n", 0, 'stamped');
 
  my $dependent_job =
    qq{bsub -K -w "ended($lsf_name)" -q production } .
    qq{-M 1000 -R 'select[mem>1000]' -R 'rusage[mem=1000]' } .
    qq{-o $logpath/exonerate_depend.out /bin/true};
 
  system($dependent_job) == 0 or
    $self->logger->error("Error submitting dependent job: $!\n");
 
  $self->logger->info("All exonerate jobs finished.\n", 0, 'stamped');
 
  #
  # check results
  #
  my @missing;
  my @error;
  
  for (my $i = 1; $i <= $num_jobs; $i++) {
  
    # check that output file exists
    my $outfile = "$dump_path/exonerate_map.$i";
    push @missing, $outfile unless (-f "$outfile");
 
    # check no errors occurred
    my $errfile = "$logpath/exonerate.$i.err";
    push @error, $errfile if (-s "$errfile");
  }
 
  if (@missing) {
    $self->logger->info("Couldn't find all exonerate output files. These are missing:\n");
    foreach (@missing) {
      $self->logger->info("$_\n", 1);
    }
 
    exit(1);
  }
 
  if (@error) {
    $self->logger->info("One or more exonerate jobs failed. Check these error files:\n");
    foreach (@error) {
      $self->logger->info("$_\n", 1);
    }
 
    exit(1);
  }
 
}
 
 
sub exon_fasta_file {
  my $self = shift;
  my $type = shift;
 
  throw("You must provide a type.") unless $type;
 
  return $self->cache->dump_path."/$type.exons.fasta";
}
 
 
sub dump_filtered_exons {
  my $self = shift;
  my $matrix = shift;
 
  unless ($matrix and
          $matrix->isa('Bio::EnsEMBL::IdMapping::ScoredMappingMatrix')) {
    throw('You must provide a ScoredMappingMatrix.');
  }
 
  # write exons to fasta files
  my $source_count = $self->write_filtered_exons('source', $matrix);
  my $target_count = $self->write_filtered_exons('target', $matrix);
 
  # return true if both source and target exons were written; otherwise we
  # don't need to run exonerate
  return (($source_count > 0) and ($target_count > 0));
}
 
 
sub write_filtered_exons {
  my $self = shift;
  my $type = shift;
  my $matrix = shift;
 
  throw("You must provide a type.") unless $type;
  unless ($matrix and
          $matrix->isa('Bio::EnsEMBL::IdMapping::ScoredMappingMatrix')) {
    throw('You must provide a ScoredMappingMatrix.');
  }
 
  $self->logger->info("\nDumping $type exons to fasta file...\n", 0, 'stamped');
 
  # don't dump exons shorter than this
  my $min_exon_length = $self->conf->param('min_exon_length') || 15;
 
  # counters
  my $total_exons = 0;
  my $dumped_exons = 0;
 
  # filehandle for fasta files
  my $fh;
  my $file = $self->exon_fasta_file($type);
  open($fh, '>', $file) or throw("Unable to open $file for writing: $!");
 
  # loop over exons, dump sequence to fasta file if longer than threshold and
  # score < 1
  EXON:
  foreach my $eid (sort { $b <=> $a }
                   keys %{ $self->cache->get_by_name('exons_by_id', $type) }) {
 
    my $exon = $self->cache->get_by_key('exons_by_id', $type, $eid);
 
    $total_exons++;
 
    # skip if exon shorter than threshold
    next EXON if ($exon->length < $min_exon_length);
 
    # skip if overlap score with any other exon is 1
    if ( $type eq 'source' ) {
      foreach my $target ( @{ $matrix->get_targets_for_source($eid) } )
      {
        if ( $matrix->get_score( $eid, $target ) > 0.9999 ) {
          next EXON;
        }
      }
    } else {
      foreach my $source ( @{ $matrix->get_sources_for_target($eid) } )
      {
        if ( $matrix->get_score( $source, $eid ) > 0.9999 ) {
          next EXON;
        }
      }
    }
 
    # write exon to fasta file
    print $fh '>', $eid, "\n", $exon->seq, "\n";
 
    $dumped_exons++;
 
  }
 
  close($fh);
 
  # log
  my $fmt = "%-30s%10s\n";
  my $size = -s $file;
  $self->logger->info(sprintf($fmt, 'Total exons:', $total_exons), 1);
  $self->logger->info(sprintf($fmt, 'Dumped exons:', $dumped_exons), 1);
  $self->logger->info(sprintf($fmt, 'Dump file size:', parse_bytes($size)), 1);
  $self->logger->info("Done.\n\n", 0, 'stamped');
 
  return $dumped_exons;
}
 
sub parse_exonerate_results {
  my ( $self, $exonerate_matrix ) = @_;
 
  unless ( defined($exonerate_matrix)
           &&
           $exonerate_matrix->isa(
                         'Bio::EnsEMBL::IdMapping::ScoredMappingMatrix')
    )
  {
    throw('You must provide a ScoredMappingMatrix.');
  }
 
  $self->logger->info( "Parsing exonerate results...\n", 0, 'stamped' );
 
  # loop over all result files
  my $dump_path = $self->cache->dump_path;
  my $num_files = 0;
  my $num_lines = 0;
 
  opendir( my $dumpdir, $dump_path ) or
    $self->logger->error("Can't open $dump_path for reading: $!");
 
  my $penalised = 0;
  my $killed    = 0;
 
  while ( defined( my $file = readdir($dumpdir) ) ) {
    unless ( $file =~ /exonerate_map\.\d+/ ) { next }
 
    $num_files++;
 
    open( my $fh, '<', "$dump_path/$file" ); 
 
    my $threshold = $self->conf->param('exonerate_threshold') || 0.5;
 
    while (<$fh>) {
      $num_lines++;
      chomp;
 
  # line format:
  # myinfo: source_id target_id match_length source_length target_length
      my ( undef, $source_id, $target_id, $match_length, $source_length,
           $target_length )
        = split;
 
      my $score = 0;
 
      if ( $source_length == 0 or $target_length == 0 ) {
        $self->logger->warning(
               "Alignment length is 0 for $source_id or $target_id.\n");
      }
      else {
        $score = 2*$match_length/( $source_length + $target_length );
 
      }
 
      if ( $score > $threshold ) {
        my $source_sr =
          $self->cache()
          ->get_by_key( 'exons_by_id', 'source', $source_id )
          ->seq_region_name();
        my $target_sr =
          $self->cache()
          ->get_by_key( 'exons_by_id', 'target', $target_id )
          ->seq_region_name();
 
        if ( $source_sr ne $target_sr ) {
          # PENALTY: The target and source are not on the same
          # seq_region.
          $score *= 0.70;
 
          # With a penalty of 0.7, exonerate scores need to be above
          # approximately 0.714 to make the 0.5 threshold.
 
          ++$penalised;
        }
 
        if ( $score > $threshold ) {
          $exonerate_matrix->add_score( $source_id, $target_id,
                                        $score );
        }
        else {
          ++$killed;
        }
      } ## end if ( $score > $threshold)
 
    } ## end while (<$fh>)
 
    close($fh);
  } ## end while ( defined( my $file...))
 
  closedir($dumpdir);
 
  $self->logger->info(
        "Done parsing $num_lines lines from $num_files result files.\n",
        0, 'stamped' );
  $self->logger->info( "Penalised $penalised exon alignments " .
                         "for not being on the same seq_region " .
                         "($killed killed).\n",
                       0,
                       'stamped' );
 
  return $exonerate_matrix;
} ## end sub parse_exonerate_results
 
 
sub non_mapped_transcript_rescore {
  my $self                = shift;
  my $matrix              = shift;
  my $transcript_mappings = shift;
 
  # argument checks
  unless ($matrix
      and $matrix->isa('Bio::EnsEMBL::IdMapping::ScoredMappingMatrix') )
  {
    throw(
       'Need a Bio::EnsEMBL::IdMapping::ScoredMappingMatrix of exons.');
  }
 
  unless ( $transcript_mappings
     and
     $transcript_mappings->isa('Bio::EnsEMBL::IdMapping::MappingList') )
  {
    throw(
         'Need a Bio::EnsEMBL::IdMapping::MappingList of transcripts.');
  }
 
  # create a lookup hash of mapped source transcripts to target
  # transcripts
  my %transcript_lookup =
    map { $_->source => $_->target }
    @{ $transcript_mappings->get_all_Entries };
 
  my $i = 0;
 
  foreach my $entry ( @{ $matrix->get_all_Entries } ) {
 
    my @source_transcripts = @{
      $self->cache->get_by_key( 'transcripts_by_exon_id', 'source',
                                $entry->source ) };
    my @target_transcripts = @{
      $self->cache->get_by_key( 'transcripts_by_exon_id', 'target',
                                $entry->target ) };
 
    my $found_mapped = 0;
 
  TR:
    foreach my $source_tr (@source_transcripts) {
      foreach my $target_tr (@target_transcripts) {
        my $mapped_target = $transcript_lookup{ $source_tr->id };
 
        if ( $mapped_target && $mapped_target == $target_tr->id ) {
          $found_mapped = 1;
          last TR;
        }
      }
    }
 
    unless ($found_mapped) {
      # PENALTY: The exon appears to belong to a transcript that has not
      # been mapped.
      $matrix->set_score( $entry->source(), $entry->target(),
                          0.9*$entry->score() );
      $i++;
    }
  } ## end foreach my $entry ( @{ $matrix...})
 
  $self->logger->debug( "Scored exons in non-mapped transcripts: $i\n",
                        1 );
} ## end sub non_mapped_transcript_rescore
 
 
 
1;