phpday 2025 - Call For Papers

gmp_popcount

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

gmp_popcountCuenta la población

Descripción

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

Obtiene el conteo de la población.

Parámetros

num

resource de número de GMP en PHP 5.5 y anterior, o un objeto de GMP en PHP 5.6 y posterior, o un string numérico siempre que sea posible convertirlo a un número.

Valores devueltos

El conteo de la población de num, como un int.

Ejemplos

Ejemplo #1 Ejemplo de gmp_popcount()

<?php
$pop1
= gmp_init("10000101", 2); // 3 1's
echo gmp_popcount($pop1) . "\n";
$pop2 = gmp_init("11111110", 2); // 7 1's
echo gmp_popcount($pop2) . "\n";
?>

El resultado del ejemplo sería:

3
7

add a note

User Contributed Notes 2 notes

up
0
ketrab2004
3 years ago
Another way to get the population count when you don't have the gmp extension is using bitwise operations:

<?php

$int
= 133; // 10000101

for($count = 0; $int != 0; $count++) // repeat until $int is 0 (and count the amount of steps it takes in $count)
{
$int = $int & $int-1; // remove the right most 1 from $int using the bitwise and operator
}

echo
$count; // 3

?>

This is Kernighan's population count.

https://youtu.be/ZRNO-ewsNcQ?t=510 has a nice explanation on how it works
up
0
phpmanual at headbank dot co dot uk
6 years ago
If you don't have gmp extension enabled (or don't want to use it for any reason), you can get popcount of an int using decbin() and substr_count().

<?php
$int1
= 133;
$bin1 = decbin($int1); // "10000101"
echo substr_count($bin1, "1");

// Result: 3
?>

Being a string-comparison this is far less efficient than gmp_popcount() (for which there is a dedicated instruction on most if not all modern processors), but may be handy if gmp is unavailable, or in non-performance-critical code that doesn't otherwise need it.
To Top