gmp_fact

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_fact — Factorial

说明

gmp_fact(GMP|int|string $num): GMP

Calculates factorial (num!) of num.

参数

num

The factorial number.

GMP 对象或 int ，或数字string。

返回值

GMP 对象。

范例

示例 #1 gmp_fact() example


<?php
$fact1 = gmp_fact(5); // 5 * 4 * 3 * 2 * 1
echo gmp_strval($fact1) . "\n";

$fact2 = gmp_fact(50); // 50 * 49 * 48, ... etc
echo gmp_strval($fact2) . "\n";
?>

以上例程会输出：

120
30414093201713378043612608166064768844377641568960512000000000000

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User Contributed Notes 2 notes

down

raholl ¶

3 years ago


I was expecting gmp_fact() is more effective than doing a while loop, but measurements show opposite:

<?php
$cislo = 112;
$fact = $cislo;
$ffact = 1;
$mt = microtime();
while($fact >= 1)
{
    $ffact = $fact * $ffact;
    $fact--;
}
$md=number_format(microtime()-$mt, 6);
echo "<h1>LOOP ($md):</h1>";
echo $ffact;

$mt = microtime();
$vec = gmp_fact($cislo);
$md=number_format(microtime()-$mt, 6);
echo "<h1>GMP FACT ($md):</h1>";
echo $vec;
exit();
?>

WILL OUTPUT:

LOOP (0.000022s):
1.9745068572211E+182

GMP FACT (0.000132s):
1.9745068572211E+182

Result is 0.000022s loop, and 0.000132s gmp_fact()

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-13

raholl ¶

3 years ago


I was expecting gmp_fact() is more effective than doing a while loop, but measurements show opposite:

<?php
$cislo = 112;
$fact = $cislo;
$ffact = 1;
$mt = microtime();
while($fact >= 1)
{
    $ffact = $fact * $ffact;
    $fact--;
}
$md=number_format(microtime()-$mt, 6);
echo "<h1>LOOP ($md):</h1>";
echo $ffact;

$mt = microtime();
$vec = gmp_fact($cislo);
$md=number_format(microtime()-$mt, 6);
echo "<h1>GMP FACT ($md):</h1>";
echo $vec;
exit();
?>

WILL OUTPUT:

LOOP (0.000022s):
1.9745068572211E+182

GMP FACT (0.000132s):
1.9745068572211E+182

Result is 0.000022s loop, and 0.000132s gmp_fact()

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