Add code

random_boolean_network.php

@@ -0,0 +1,93 @@
+<?php
+
+/*
+    Random boolean network in PHP (7.4+).
+    Inspired by the Computerphile Video: https://www.youtube.com/watch?v=mCML2B94rUg
+    The use of random_int combined with modulo leads to better randomness entropy.
+    Formally correct as the relations with other cells are bitshifted in the right order.
+    Not that it matters, as it's randomly chosen, but done anyway for the sake of repeatability.
+
+    Joop Schilder
+    Sat 14 Nov 01:30
+
+    One of the nights that I shall remember as if it were me who was in control of my brain.
+*/
+
+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++) {
+    $truth_table[$i] = random_int(0, 100) % 2; 
+}
+
+$nodes = [];
+for ($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++) {
+            $tt_index += $nodes[$connections[$i][$j]] << (NUM_CONNECTIONS - 1 - $j); 
+        }
+        $next_nodes[$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);
+}