mirror of
https://github.com/sbrl/Pepperminty-Wiki.git
synced 2024-12-28 03:34:56 +00:00
401 lines
14 KiB
PHP
401 lines
14 KiB
PHP
<?php
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
|
|
|
|
require_once("JsonStorageBox.php");
|
|
|
|
/**
|
|
* Calculates the standard deviation of an array of numbers.
|
|
* @source https://stackoverflow.com/a/57694168/1460422
|
|
* @param array $array The array of numbers to calculate the standard deviation of.
|
|
* @return float The standard deviation of the numbers in the given array.
|
|
*/
|
|
function standard_deviation(array $array): float {
|
|
$size = count($array);
|
|
$mean = array_sum($array) / $size;
|
|
$squares = array_map(function ($x) use ($mean) {
|
|
return pow($x - $mean, 2);
|
|
}, $array);
|
|
|
|
return sqrt(array_sum($squares) / ($size - 1));
|
|
}
|
|
|
|
/**
|
|
* A serialisable BK-Tree Implementation.
|
|
* Ref: https://nullwords.wordpress.com/2013/03/13/the-bk-tree-a-data-structure-for-spell-checking/
|
|
*/
|
|
class BkTree
|
|
{
|
|
private $box = null;
|
|
|
|
private $nodes = [];
|
|
|
|
// private $touched_ids = [];
|
|
|
|
private $cost_insert = 1;
|
|
private $cost_delete = 1;
|
|
private $cost_replace = 1;
|
|
|
|
public function __construct($filename) {
|
|
$this->box = new JsonStorageBox($filename);
|
|
}
|
|
|
|
/**
|
|
* A utility function for calculating edit distance.
|
|
* Warning: Do not use this internally! It is *slow*. It's much faster to do this directly. This exists only for external use.
|
|
* @param string $a The first string.
|
|
* @param string $b The second string to compare against.
|
|
* @return int The computed edit distance.
|
|
*/
|
|
public function edit_distance(string $a, string $b) : int {
|
|
return levenshtein($a, $b, $this->cost_insert, $this->cost_replace, $this->cost_delete);
|
|
}
|
|
|
|
private function get_node_count() : int {
|
|
if(!$this->box->has("node_count"))
|
|
$this->set_node_count(0);
|
|
return $this->box->get("node_count");
|
|
}
|
|
private function set_node_count(int $value) {
|
|
$this->box->set("node_count", $value);
|
|
}
|
|
private function increment_node_count() {
|
|
$this->box->set("node_count", $this->box->get("node_count") + 1);
|
|
}
|
|
|
|
/**
|
|
* Adds a string to the tree.
|
|
* @param string $string The string to add.
|
|
* @param int $starting_node_id The id fo node to start insertion from. Defaults to 0 - for internal use only.
|
|
* @return int The depth at which the new node was added.
|
|
*/
|
|
public function add(string $string, int $starting_node_id = 0) : int {
|
|
// FUTURE: When we support deletes, we'll need to ensure that the root node is handled correctly
|
|
if(!$this->box->has("node|0")) {
|
|
// If the root node of the tree doesn't exist, create it
|
|
$new = new stdClass();
|
|
$new->value = $string;
|
|
$new->children = new stdClass(); // [ "id" => int, "distance" => int ]
|
|
$this->box->set("node|0", $new);
|
|
$this->touched_ids[] = 0;
|
|
$this->increment_node_count();
|
|
return 0;
|
|
}
|
|
|
|
if(!$this->box->has("node|$starting_node_id"))
|
|
throw new Exception("Error: Failed to find node with id $starting_node_id to begin insertion");
|
|
|
|
// if($string == "bunny") echo("\nStart $string\n");
|
|
|
|
$next_node = $this->box->get("node|$starting_node_id"); // Grab the root to start with
|
|
$next_node_id = $starting_node_id;
|
|
$depth = 0; $visted = 0;
|
|
while(true) {
|
|
$visted++;
|
|
$distance = levenshtein($string, $next_node->value, $this->cost_insert, $this->cost_replace, $this->cost_delete);
|
|
|
|
// if($string == "bunny") echo("$visted: Visiting $next_node->value, distance $distance (child distances ".implode(", ", array_map(function($el) { return $el->distance; }, $next_node->children)).")\n");
|
|
|
|
if(isset($next_node->children->$distance)) {
|
|
$child_id = $next_node->children->$distance;
|
|
$next_node = $this->box->get("node|$child_id");
|
|
$next_node_id = $child_id;
|
|
// if($string == "cake") echo("Identical distance as {$next_node["value"]}, restarting loop\n");
|
|
$depth++;
|
|
continue; // Continue on the outer while loop
|
|
}
|
|
|
|
// if($string == "bunny") echo("Inserting on $next_node->value\n");
|
|
|
|
// If we got here, then no existing children have the same edit distance
|
|
// Note that here we don't push to avoid the overhead from either array_push() (considerable) or count() (also considerable).
|
|
|
|
// Create the new child node
|
|
$new_id = $this->get_node_count();
|
|
$this->box->set("node|$new_id", (object) [
|
|
"value" => $string,
|
|
"children" => new stdClass()
|
|
]);
|
|
// Create the edge that points from the existing node to the new node
|
|
$next_node->children->$distance = $new_id;
|
|
$this->box->set("node|$next_node_id", $next_node);
|
|
$this->increment_node_count();
|
|
break;
|
|
}
|
|
return $depth;
|
|
}
|
|
|
|
/**
|
|
* Removes a string from the tree.
|
|
* @param string $string The string to remove.
|
|
* @return bool Whether the removal was successful.
|
|
*/
|
|
public function remove(string $string) : bool {
|
|
$stack = [ [ "node" => $this->box->get("node|0"), "id" => 0 ] ];
|
|
$node_target = $stack[0]["node"];
|
|
$node_target_id = 0;
|
|
|
|
while($node_target->value !== $string) {
|
|
$distance = levenshtein($string, $node_target->value, $this->cost_insert, $this->cost_replace, $this->cost_delete);
|
|
|
|
// Failed to recurse to find the node with the value in question
|
|
if(!isset($node_target->children->$distance))
|
|
return false;
|
|
|
|
$node_target_id = $node_target->children->$distance;
|
|
$node_target = $this->box->get("node|$node_target_id");
|
|
$stack[] = [ "node" => $node_target, "id" => $node_target_id ];
|
|
}
|
|
|
|
// The last item but 1 on the stack is the parent node
|
|
$parent = $stack[count($stack) - 2];
|
|
|
|
// 1. Delete the connection from parent -> target
|
|
foreach($parent["node"]->children as $distance => $id) {
|
|
if($id == $node_target_id) {
|
|
unset($parent["node"]->children->$distance);
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Save the parent node's back to disk
|
|
// Note that we do this *before* sorting out the orphans, since it's possible that $this->add() will modify it further
|
|
$this->box->set("node|{$parent["id"]}", $parent["node"]);
|
|
|
|
// 2. Iterate over the target's children (if any) and re-hang them from the parent
|
|
// NOTE: We need to be careful that the characteristics of the tree are preserved. We should test this by tracing a node's location in the tree and purposefully removing nodes in the chain and see if the results returned as still the same
|
|
//
|
|
// Hang the now orphaned children and all their decendants from the parent
|
|
foreach($node_target->children as $distance => $id) {
|
|
$orphan = $this->box->get("node|$id");
|
|
$substack = [ [ "node" => $orphan, "id" => $id ] ]; $substack_top = 0;
|
|
while($substack_top >= 0) {
|
|
$next = $substack[$substack_top];
|
|
unset($substack[$substack_top]);
|
|
$substack_top--;
|
|
|
|
$this->box->delete("node|{$next["id"]}"); // Delete the orphan node
|
|
$this->add($next["node"]->value, $parent["id"]); // Re-hang it from the parent
|
|
|
|
foreach($next["node"]->children as $distance => $sub_id) {
|
|
$substack[++$substack_top] = [
|
|
"node" => $this->box->get("node|$sub_id"),
|
|
"id" => $sub_id
|
|
];
|
|
}
|
|
}
|
|
}
|
|
|
|
// Delete the target node
|
|
$this->box->delete("node|$node_target_id");
|
|
|
|
return true;
|
|
}
|
|
|
|
public function trace(string $string) {
|
|
$stack = [
|
|
(object) [ "node" => $this->box->get("node|0"), "id" => 0 ]
|
|
];
|
|
$node_target = $stack[0]->node;
|
|
|
|
while($node_target->value !== $string) {
|
|
$distance = levenshtein($string, $node_target->value, $this->cost_insert, $this->cost_replace, $this->cost_delete);
|
|
|
|
var_dump($node_target);
|
|
|
|
// Failed to recurse to find the node with the value in question
|
|
if(!isset($node_target->children->$distance))
|
|
return null;
|
|
|
|
$node_target_id = $node_target->children->$distance;
|
|
$node_target = $this->box->get("node|$node_target_id");
|
|
$stack[] = (object) [ "node" => $node_target, "id" => $node_target_id ];
|
|
}
|
|
return $stack;
|
|
}
|
|
|
|
/**
|
|
* Convenience function that returns just the first result when looking up a string.
|
|
* @param string $string The string to lookup
|
|
* @param integer $distance The maximum edit distance to search.
|
|
* @return string|null The first matching string, or null if no results were found.
|
|
*/
|
|
public function lookup_one(string $string, int $distance = 1) {
|
|
$result = $this->lookup($string, $distance, 1);
|
|
if(empty($result)) return null;
|
|
return $result[0];
|
|
|
|
// foreach($this->lookup($string, $distance) as $item)
|
|
// return $item;
|
|
}
|
|
|
|
/**
|
|
* Generator that walks the BK-Tree and iteratively yields results.
|
|
* TODO: Refactor this to use an array, since generators are ~
|
|
* @param string $string The search string.
|
|
* @param integer $max_distance The maximum edit distance to search.
|
|
* @param integer $count The number of results to return. 0 = All results found. Note that results will be in a random order.
|
|
* @return Generator<string> Iteratively yielded similar resultant strings from the BK-Tree.
|
|
*/
|
|
public function lookup(string $string, int $max_distance = 1, int $count = 0) {
|
|
if($this->get_node_count() == 0) return null;
|
|
|
|
$result = []; $result_count = 0;
|
|
$stack = [ $this->box->get("node|0") ];
|
|
$stack_top = 0;
|
|
|
|
// https://softwareengineering.stackexchange.com/a/226162/58491
|
|
while($stack_top >= 0) {
|
|
// Take the topmost node off the stack
|
|
$node_current = $stack[$stack_top];
|
|
unset($stack[$stack_top]);
|
|
$stack_top--;
|
|
|
|
$distance = levenshtein($string, $node_current->value, $this->cost_insert, $this->cost_replace, $this->cost_delete);
|
|
|
|
/*
|
|
echo("[lookup] Visiting $node_current->value (distance $distance, child distances ".implode(", ", array_map(function($el) { return $el->distance; }, $node_current->children)).")\n");
|
|
|
|
if(in_array($node_current->value, ["worlds", "domicil", "mealiest", "stopgaps", "pibroch", "upwardly", "nontruth", "vizoring"])) {
|
|
echo("[lookup] Children: ".implode(", ", array_map(function($el) {
|
|
return "$el->distance: ".$this->box->get("node|$el->id")->value;
|
|
}, $node_current->children))."\n");
|
|
}
|
|
if($node_current->value == "bunny") exit();
|
|
*/
|
|
|
|
// If the edit distance from the target string to this node is within the tolerance, yield it
|
|
if($distance <= $max_distance) {
|
|
// readline("press any key to continue");
|
|
$result[] = $node_current->value;
|
|
if($count != 0 && $result_count >= $count) break;
|
|
// yield $node_current["value"];
|
|
}
|
|
|
|
// Adding the key here speeds it up, apparently
|
|
// Ref: https://phpbench.com/
|
|
for($child_distance = $distance - $max_distance; $child_distance <= $distance + $max_distance; $child_distance++) {
|
|
if(!isset($node_current->children->$child_distance))
|
|
continue;
|
|
|
|
// echo("[lookup] Recursing on child ".$this->box->get("node|$child->id")->value." (distance $child->distance)\n");
|
|
// Push the node onto the stack
|
|
// Note that it doesn't actually matter that the stack isn't an accurate representation of ancestor nodes at any given time here. The stack is really a hybrid between a stack and a queue, having features of both.
|
|
$stack[++$stack_top] = $this->box->get("node|{$node_current->children->$child_distance}");
|
|
}
|
|
}
|
|
|
|
return $result;
|
|
}
|
|
|
|
/**
|
|
* Calculate statistics about the BK-Tree.
|
|
* Useful for analysing a tree's structure.
|
|
* If the tree isn't balanced, you may need to insert items in a different order.
|
|
* @return array An array of statistics about this BK-Tree.
|
|
*/
|
|
public function stats() {
|
|
$result = [
|
|
"depth_max" => 0,
|
|
"depth_min_leaf" => INF,
|
|
"depth_average" => 0,
|
|
"depth_average_noleaf" => 0,
|
|
"depth_standard_deviation" => [],
|
|
"child_count_average" => 0,
|
|
"child_count_max" => 0,
|
|
"nodes" => $this->get_node_count(),
|
|
"leaves" => 0,
|
|
"non_leaves" => 0
|
|
];
|
|
|
|
$start_time = microtime(true);
|
|
|
|
$stack = [ [ "node" => $this->box->get("node|0"), "depth" => 0 ] ];
|
|
|
|
// https://softwareengineering.stackexchange.com/a/226162/58491
|
|
while(!empty($stack)) {
|
|
// Take the top-most node off the stack
|
|
$current = array_pop($stack);
|
|
|
|
// echo("Visiting "); var_dump($current);
|
|
|
|
// Operate on the node
|
|
$result["depth_standard_deviation"][] = $current["depth"];
|
|
$result["depth_average"] += $current["depth"];
|
|
if($current["depth"] > $result["depth_max"])
|
|
$result["depth_max"] = $current["depth"];
|
|
if(empty($current["node"]->children) && $current["depth"] < $result["depth_min_leaf"])
|
|
$result["depth_min_leaf"] = $current["depth"];
|
|
|
|
$child_count = count((array)($current["node"]->children));
|
|
$result["child_count_average"] += $child_count;
|
|
if($child_count > $result["child_count_max"])
|
|
$result["child_count_max"] = $child_count;
|
|
if($child_count > 0) {
|
|
$result["depth_average_noleaf"] += $current["depth"];
|
|
$result["non_leaves"]++;
|
|
}
|
|
else
|
|
$result["leaves"]++;
|
|
|
|
// Iterate over the child nodes
|
|
foreach($current["node"]->children as $child_distance => $child_id) {
|
|
$stack[] = [
|
|
"node" => $this->box->get("node|$child_id"),
|
|
"depth" => $current["depth"] + 1
|
|
];
|
|
}
|
|
}
|
|
$result["depth_average"] /= $result["nodes"];
|
|
$result["depth_average_noleaf"] /= $result["non_leaves"];
|
|
$result["child_count_average"] /= $result["nodes"];
|
|
$result["depth_standard_deviation"] = standard_deviation($result["depth_standard_deviation"]);
|
|
|
|
$result["time_taken"] = microtime(true) - $start_time;
|
|
|
|
return $result;
|
|
}
|
|
|
|
public function walk() {
|
|
$stack = [ (object)[
|
|
"id" => 0,
|
|
"node" => $this->box->get("node|0"),
|
|
"parent_id" => -1,
|
|
"parent" => null,
|
|
"depth" => 0
|
|
] ];
|
|
$stack_top = 0;
|
|
|
|
// https://softwareengineering.stackexchange.com/a/226162/58491
|
|
while(!empty($stack)) {
|
|
// Take the topmost node off the stack
|
|
$current = $stack[$stack_top];
|
|
unset($stack[$stack_top]);
|
|
$stack_top--;
|
|
|
|
// echo("Visiting "); var_dump($current);
|
|
yield $current;
|
|
|
|
// Iterate over the child nodes
|
|
foreach($current->node->children as $child_distance => $child_id) {
|
|
$stack_top++;
|
|
$stack[$stack_top] = (object) [
|
|
"id" => $child_id,
|
|
"node" => $this->box->get("node|{$current->node->children->$child_distance}"),
|
|
"parent_id" => $current->id,
|
|
"parent" => $current->node,
|
|
"depth" => $current->depth + 1
|
|
];
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Saves changes to the tree back to disk.
|
|
* @return void
|
|
*/
|
|
public function close() {
|
|
$this->box->close();
|
|
}
|
|
}
|