Hi, all, I have wrote a program to compute the largest common substrings of two sentences on the word level. Below is the code: 
sub lc_substr {
  my ($s, $t) = @_; 
  my $z = 0;
 
  my @S = (undef, split(/ /, $s));
  my @T = (undef, split(/ /, $t));
  
  my $m = scalar @S; 
  my $n = scalar @T; 

  my @LCS = ();
  my @start = ();
  my @end = ();
 
  for my $i ( 1 .. $m ) { 
    for my $j ( 1 .. $n ) {
      if ($S[$i] =~ m/^$T[$j]$/ig && $S[$i] ne undef && $T[$j] ne unde
+f &&$S[$i] ne " "&&$T[$j] ne " ") {
        $L[$i-1][$j-1] ||= 0;  
        $L[$i][$j] = $L[$i-1][$j-1] + 1;
        if ($L[$i][$j] > $z) {
          $z = $L[$i][$j];
          @ret = (); 
          @start = ();
          @end = ();
          @prod = ();
        }
        if ($L[$i][$j] == $z) {
          $start = $i-$z+1;
          $end = $i;
          push(@start,$start);
          push(@end,$end);
          push(@prod,$t);
        }
      }
    }
  }  
  
   $num = scalar @start;
   for ($n = 0; $n < $num;$n++){
      if($prod[$n] ne ""){
         $str = $prod[$n]." "."[".$start[$n].",".$end[$n]."]";
         push (@LCS, $str);
      }
   }   
   return @LCS;  
}

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This function would return all the longest consecutive words between these two sentnces. The problem is right now I have two lists of over 4000 sentnces to compare, while using this function is extremly slow. Is there a way to accelerate this function? thanks in advance. Zhe

In reply to LCS efficiency problem by zhe

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