sub tpgSearch
{
  my ($ref, $val, $min, $max) = @_;
  return undef if($max==$min);
  return $min if($$ref[$min]==$val);
  return $max if($$ref[$max]==$val);
  my $diff=($ids[$max]-$ids[$min])/($max-$min);
  my $pos=$min+int(($val-$ids[$min])/$diff);

  if($$ref[$pos]==$val)
  { return $pos; }
  else
  {
   if($$ref[$pos]<$val)
   {
    my $n_max=$pos+int(($val-$$ref[$pos])/$diff);
    $max=$n_max<@{$ref}?$n_max:@{$ref};
    $min=$pos;
    if($min==$max)
    {
     $pos++ while($$ref[$pos]<$val);
     return $$ref[$pos]==$val?$pos:undef;
    }
   }
 
   if($$ref[$pos]>$val)
   {
    my $n_min=$pos-int(($$ref[$pos]-$val)/$diff);
    $min=$n_min>0?$n_min:0;
    $max=$pos;
    if($min==$max)
    {
     $pos-- while($$ref[$pos]>$val);
     return $$ref[$pos]==$val?$pos:undef;
    }
   }
   return tpgSearch($ref,$val,$min,$max);
  } 
}