1: Two years ago, when a colleague had root access to our
   2: lab's SUN 4500s (8 processors each, each running at 500mhz),
   3: we decided that all those spare processor cycles were
   4: going to waste.  With his knowledge of UNIX calls and
   5: my affinity for perl, we came up with a SETI runner which
   6: fired up new instances when the system was idle, and
   7: killed instances when the system load went up.
   8: 
   9: 
  10: my $uptime       = "uptime";  # or whatever it's called...
  11: 
  12: my $setiRoot     = '/usr/bin/seti';
  13: my $setiBinary   = 'setiathome';
  14: my $setiFlags    = '';
  15: my $setiLog      = 'seti.log';
  16: 
  17: my $napTime      = 2;
  18: 
  19: my $maxInstances = 8;    # maximum number of SETI instances
  20: my $minInstances = 0;    # minimum number of SETI instances
  21: my $lowThreshold = 8.00; # start SETI
  22: my $hiThreshold  = 9.00; # stop SETI
  23: 
  24: my @setiPids;            # pid array
  25: 
  26: while(1)
  27: {
  28:    sleep( $napTime );
  29:    
  30:    my $uptime = `$uptime`;
  31:    
  32:    $uptime = $1 if $uptime =~ /load average: (\d+\.\d\d)/;
  33: 
  34:    print STDERR "load average: $uptime\n";
  35:    
  36:    #
  37:    # if the uptime is below a certain load,
  38:    # then fire up a new SETI instance.
  39:    #
  40:    &startSETI
  41:       if ( ($uptime < $lowThreshold) && (@seti < $maxInstances) );
  42:    
  43:    #
  44:    # if the uptime is above a certain load,
  45:    # then kill a SETI instance.
  46:    #
  47:    &stopSETI
  48:       if ( ($uptime > $hiThreshold) && (@seti > $minInstances) );
  49: }
  50: 
  51: #
  52: # Organize our list of PIDs
  53: #
  54: sub startSETI
  55: {
  56:    print STDERR "Firing up a SETI...\n";
  57:    print STDERR "We have ", scalar( @setiPids ), " PIDs:\n";
  58:    print STDERR join( " ", @setiPids ), "\n";
  59:    # list all processes
  60:    my $number = scalar( @setiPids );
  61:       
  62:    chdir( "$setiRoot/seti$number" );
  63:    
  64:    print STDERR "Working directory: $setiRoot/seti$number\n";
  65:    
  66:    push( @setiPids, `$setiBinary $setiFlags > $setiLog` );
  67: }
  68: 
  69: #
  70: # Quick and dirty killer
  71: #
  72: sub stopSETI
  73: {
  74:    print STDERR "Shutting down a SETI...\n";
  75:    
  76:    kill 9, pop @setiPids;
  77: }