Mgccl's Ivory Towerso tired

bcroot(2,3072);

//Version 0.3 of BCRoot
//Change Log: It uses a lot bcsqrt() to make the speed fast
//fix a small decimal bug, where the last decimal could be wrong
//fix important bug.
 
fufunction bcroot($a, $n, $scale='default'){
    $default = bcgetscale();//Get the scale
    if($scale == 'default'){
        $scale = $default;//use default scale
    }
    $limit = ceil(log($scale+15)/log(2))+1;
    if($n & ($n-1)){//check if $n is the power of 2, return 0 if is
        //decbin is the reason this function can't have number
        //larger than 2^31
        $bin = decbin($n);
		$i = strlen($bin)-1;
		$pow = 0;
		while($i){
			if($bin[$i]==='0'){
				++$pow; --$i;
			}else{
				break;
			}
		}
		$n = bcdiv($n, bcpow(2, $pow),0);
       //now use Newton?s method to find the number
        $x = 1;
        $k = 0;
        bcscale($scale*$limit);
        while($k<$limit*$scale){
            $t1 = bcdiv(1,$n);
            $t21 = bcmul(bcsub($n,1),$x);
            $t22 = bcdiv($a,bcpow($x, $n-1));
            $t2 = bcadd($t21,$t22);
            $x = bcmul($t1, $t2);
            ++$k;
        }
        $i = 0;
        while($i < $pow){
            $x = bcsqrt($x,$scale+3);
            ++$i;
        }
        $x = bcadd($x,0,$scale+1);
    }else{
    //here use many bcsqrt, because this is FAST
        $i = 0;
        $pow = log($n)/log(2);
        while($i < $pow){
            $a = bcsqrt($a,$scale*$limit);
            ++$i;
        }
        $x = bcadd($a,0,$scale+1);
    }
    bcscale($default);
    return bcround($x,$scale);
}
 
function bcround($x,$scale){
	if($x[strlen($x)-1]<5){
    	$x = bcadd($x,0,$scale);
    }else{
    	$y = str_replace(array('1','2','3','4','5','6','7','8','9'),0,$x);
    	$y[strlen($y)-1] = 10 - $x[strlen($x)-1];
    	$x = bcadd(bcadd($x,$y,$scale+1),0,$scale);
    }
	return $x;
}