source code
<?
/*
The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
contributed by Isaac Gouy
multicore by anon
*/
function A(&$i, &$j){
return 1.0 / ( ( ( ($i+$j) * ($i+$j+1) ) >> 1 ) + $i + 1 );
}
function Av(&$n,&$v,&$start,&$end){
global $_tpl;
$Av = $_tpl;
for ($i = $start; $i < $end; ++$i) {
$sum = 0.0;
foreach($v as $j=>$v_j) {
$sum += A($i,$j) * $v_j;
}
$Av[$i] = $sum;
}
return $Av;
}
function Atv(&$n,&$v,&$start,&$end){
global $_tpl;
$Atv = $_tpl;
for($i = $start; $i < $end; ++$i) {
$sum = 0.0;
foreach($v as $j=>$v_j) {
$sum += A($j,$i) * $v_j;
}
$Atv[$i] = $sum;
}
return $Atv;
}
function AtAv(&$n,&$v,&$start,&$end,&$sync){
$tmp = Av($n, $v, $start, $end);
if ($sync) sync($tmp);
$tmp = Atv($n, $tmp, $start, $end);
if ($sync) sync($tmp);
return $tmp;
}
function sync(&$tmp) {
global $parent,$chunk_data_size,$total_data_size,$pipe,$pipes;
if (!$parent) {
array_unshift($tmp, 'd*');
$data = call_user_func_array('pack', $tmp);
safe_write($pipe, $data);
$tmp = array_merge(array(), unpack('d*', safe_read($pipe, $total_data_size)));
} else {
$tmps = array(array('d*'));
foreach($pipes as $pipe) {
$tmps[] = unpack('d*', safe_read($pipe, $chunk_data_size));
}
$tmps[] = &$tmp;
$tmp = call_user_func_array('array_merge', $tmps);
$data = call_user_func_array('pack', $tmp);
foreach($pipes as $pipe) {
safe_write($pipe, $data);
}
array_shift($tmp);
}
}
function safe_write($fd, $data) {
$len = strlen($data);
do {
$w = fwrite($fd, $data);
$len -= $w;
} while($len && ($data = substr($data, $w)) !== FALSE);
}
function safe_read($fd, $len) {
$data = '';
while ($len > 0) {
$d = fread($fd, $len);
$len -= strlen($d);
$data .= $d;
}
return $data;
}
function pipe() {
return stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, 0);
}
$n = (int) (($argc == 2) ? $argv[1] : 1);
$procs = 1;
if (file_exists('/proc/cpuinfo')) {
$procs = preg_match_all('/^processor\s/m', file_get_contents('/proc/cpuinfo'), $discard);
}
if ($n < $procs) {
$procs = 1;
}
$chunk_size = (int) ($n / $procs);
$double_size = strlen(pack('d', 0.0));
$chunk_data_size = $double_size * $chunk_size;
$total_data_size = $double_size * $n;
$pipes = array();
$parent = FALSE;
for($i = 0; $i < $procs; ++$i) {
$range_begin = $i * $chunk_size;
if ($i < ($procs - 1)) {
$pipe = pipe();
$pipes[] = $pipe[0];
$pipe = $pipe[1];
$range_end = $range_begin + $chunk_size;
$pid = pcntl_fork();
if ($pid === -1) {
die('could not fork');
} else if ($pid) {
continue;
}
break;
} else {
$range_end = $n;
$parent = TRUE;
}
}
$u = array_fill(0, $n, 1.0);
$_tpl = array_fill($range_begin, $range_end - $range_begin, 0.0);
$sync = $procs > 0;
for ($i=0; $i<10; $i++){
$v = AtAv($n,$u,$range_begin,$range_end,$sync);
$u = AtAv($n,$v,$range_begin,$range_end,$sync);
}
if (!$parent) {
exit(0);
}
$childs = $procs - 1;
while ($childs--) {
pcntl_wait($s);
}
$vBv = 0.0;
$vv = 0.0;
$i = 0;
foreach($v as $val) {
$vBv += $u[$i]*$val;
$vv += $val*$val;
++$i;
}
printf("%0.9f\n", sqrt($vBv/$vv));