# ---------------------------------------------------------------------------# pi.perl  computes pi (3.14...) about 5120 Digits## W. Kebsch, July-1988  {uunet!mcvax}!unido!nixpbe!kebsch$my_name = $0;$version = $my_name . "-1.2";# some working parameter$smax =  5120;          # max digits$lmax =     4;          # digits per one array element$hmax = 10000;          # one array element contains: 0..9999$smin = $lmax;          # min digits$mag  =     7;          # magic number# subroutinessub mul_tm              # multiply the tm array with a long value{    $cb = pop(@_);      # elements(array)    $x  = pop(@_);      # value    $c = 0;    for($i = 1; $i <= $cb; $i++)    {	$z      = $tm[$i] * $x + $c;	$c      = int($z / $hmax);	$tm[$i] = $z - $c * $hmax;    }}sub mul_pm              # multiply the pm array with a long value{    $cb = pop(@_);      # elements(array)    $x  = pop(@_);      # value    $c = 0;    for($i = 1; $i <= $cb; $i++)    {	$z      = $pm[$i] * $x + $c;	$c      = int($z / $hmax);	$pm[$i] = $z - $c * $hmax;    }}sub divide              # divide the tm array by a long value{    $cb = pop(@_);      # elements(array)    $x  = pop(@_);      # value    $c = 0;    for($i = $cb; $i >= 1; $i--)    {	$z      = $tm[$i] + $c;	$q      = int($z / $x);	$tm[$i] = $q;	$c      = ($z - $q * $x) * $hmax;    }}sub add                 # add tm array to pm array{    $cb = pop(@_);      # elements(array)    $c = 0;    for($i = 1; $i <= $cb; $i++)    {	$z = $pm[$i] + $tm[$i] + $c;	if($z >= $hmax)	{	    $pm[$i] = $z - $hmax;	    $c      = 1;	}	else	{	    $pm[$i] = $z;	    $c      = 0;	}    }}$m0 = 0; $m1 = 0; $m2 = 0;sub check_xb            # reduce current no. of elements (speed up!){    $cb = pop(@_);      # current no. of elements    if(($pm[$cb] == $m0) && ($pm[$cb - 1] == $m1) && ($pm[$cb - 2] == $m2))    {	$cb--;    }    $m0 = $pm[$cb];    $m1 = $pm[$cb - 1];    $m2 = $pm[$cb - 2];    $cb;}sub display             # show the result{    $cb = pop(@_);      # elements(array);    printf("\n%3d.", $pm[$cb]);    $j = $mag - $lmax;    for($i = $cb - 1; $i >= $j; $i--)    {	printf(" %04d", $pm[$i]);    }    print "\n";}sub the_job             # let's do the job{    $s = pop(@_);       # no. of digits    $s  = int(($s + $lmax - 1) / $lmax) * $lmax;    $b  = int($s / $lmax) + $mag - $lmax;    $xb = $b;    $t  = int($s * 5 / 3);    for($i = 1; $i <= $b; $i++)         # init arrays    {	$pm[$i] = 0;	$tm[$i] = 0;    }    $pm[$b - 1] = $hmax / 2;    $tm[$b - 1] = $hmax / 2;    printf("digits:%5d, terms:%5d, elements:%5d\n", $s, $t, $b);    for($n = 1; $n <= $t; $n++)    {	printf("\r\t\t\t  term:%5d", $n);	if($n < 200)	{	    do mul_tm((4 * ($n * $n - $n) + 1), $xb);	}	else	{	    do mul_tm((2 * $n - 1), $xb);	    do mul_tm((2 * $n - 1), $xb);	}	if($n < 100)	{	    do divide(($n * (16 * $n + 8)), $xb);	}	else	{	    do divide((8 * $n), $xb);	    do divide((2 * $n + 1), $xb);	}	do add($xb);	if($xb > $mag)	{	    $xb = do check_xb($xb);	}    }    do mul_pm(6, $b);    do display($b);    ($user,$sys,$cuser,$csys) = times;    printf("\n[u=%g  s=%g  cu=%g  cs=%g]\n",$user, $sys, $cuser, $csys);}# main block ----------------------------------------------------------------$no_of_args = $#ARGV + 1;print("$version, ");die("usage: $my_name <no. of digits>") unless($no_of_args == 1);$digits = int($ARGV[0]);die("no. of digits out of range [$smin\..$smax]")			    unless(($digits >= $smin) && ($digits <= $smax));do the_job($digits);exit 0;# That's all ----------------------------------------------------------------