random-boolean-network/random_boolean_network.php

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2020-11-14 11:16:17 +01:00
<?php
/*
Random boolean network in PHP (7.4+).
Inspired by the Computerphile Video: https://www.youtube.com/watch?v=mCML2B94rUg
Joop Schilder
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Fri 13 Nov
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*/
const NUM_NODES = 20;
const NUM_CONNECTIONS = 3;
const NUM_GENERATIONS = 20;
const CHAR_ON_ZERO = '0';
const CHAR_ON_ONE = ' ';
const TRUTH_TABLE_SIZE = (1 << NUM_CONNECTIONS);
$truth_table = [];
for ($i = 0; $i < TRUTH_TABLE_SIZE; $i++) {
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$truth_table[$i] = random_int(0, 100) % 2;
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}
$nodes = [];
for ($i = 0; $i < NUM_NODES; $i++) {
$nodes[$i] = random_int(0, 100) % 2;
}
$connections = [];
for ($i = 0; $i < NUM_NODES; $i++) {
for ($j = 0; $j < NUM_CONNECTIONS; $j++) {
$connections[$i][$j] = random_int(0, 2000) % 20;
}
}
function print_generation(int $g, array $nodes): void
{
printf("G%5d %s\n", $g, format_nodes($nodes));
}
function print_truth_table(array $truth_table): void
{
print("Truth table:\n");
for($i = 0; $i < TRUTH_TABLE_SIZE; $i++) {
printf("[%s] => %d\n", str_pad(decbin($i), NUM_CONNECTIONS, '0', STR_PAD_LEFT), $truth_table[$i]);
}
}
function print_connections(array $connections): void
{
print("Connections:\n");
for ($i = 0; $i < NUM_NODES; $i++) {
printf("[%3d] => [%s]\n", $i, implode(', ', $connections[$i]));
}
}
function format_nodes(array $nodes): string
{
return implode(' ', array_map(fn($i): string => $i == 0 ? CHAR_ON_ZERO : CHAR_ON_ONE, $nodes));
}
function propagate(array $nodes, array &$connections, array &$truth_table): array
{
$next_nodes = [];
for ($i = 0; $i < NUM_NODES; $i++) {
$tt_index = 0;
for ($j = 0; $j < NUM_CONNECTIONS; $j++) {
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$tt_index += $nodes[$connections[$i][$j]] << (NUM_CONNECTIONS - 1 - $j);
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}
$next_nodes[$i] = $truth_table[$tt_index];
}
return $next_nodes;
}
print_truth_table($truth_table);
print("\n");
print_connections($connections);
print("\n");
print_generation(0, $nodes);
for ($i = 0; $i < NUM_GENERATIONS; $i++) {
$nodes = propagate($nodes, $connections, $truth_table);
print_generation($i, $nodes);
}