function f()
{
global $_tpl;
#$n = intval(($argc == 2) ? $argv[1] : 400);
$n = 400;
$u = array_fill(0, $n, 1.0);
$_tpl = array_fill(0, $n, 0.0);
for ($i = 0; $i < 10; $i++) {
$v = AtAv($n, $u);
$u = AtAv($n, $v);
}
$vBv = 0.0;
$vv = 0.0;
$i = 0;
foreach ($v as $val) {
$vBv += $u[$i] * $val;
$vv += $val * $val;
++$i;
}
sqrt($vBv / $vv);
}
if ($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;
$Atv = $_tpl;
for ($i = 0; $i < $n; ++$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)
{
$tmp = Av($n, $v);
return Atv($n, $tmp);
}
$n = intval($argc == 2 ? $argv[1] : 1);
$u = array_fill(0, $n, 1.0);
$_tpl = array_fill(0, $n, 0.0);
for ($i = 0; $i < 10; $i++) {
$v = AtAv($n, $u);
$u = AtAv($n, $v);
}
$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 / $vv));
function spectral_norm($n = 200)
{
$u = array_pad(array(), $n, 1);
for ($i = 0; $i < 10; $i++) {
$v = AtAv($n, $u);
$u = AtAv($n, $v);
}
$vBv = 0;
$vv = 0;
for ($i = 0; $i < $n; $i++) {
$vBv += $u[$i] * $v[$i];
$vv += $v[$i] * $v[$i];
}
printf("%0.9f\n", sqrt($vBv / $vv));
}
private static function spectralnorm($n)
{
//$n = (int) (($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));
}