1
|
|
|
<?php |
2
|
|
|
|
3
|
|
|
/** |
4
|
|
|
* Box packing (3D bin packing, knapsack problem). |
5
|
|
|
* |
6
|
|
|
* @author Doug Wright |
7
|
|
|
*/ |
8
|
|
|
declare(strict_types=1); |
9
|
|
|
|
10
|
|
|
namespace DVDoug\BoxPacker; |
11
|
|
|
|
12
|
|
|
use Psr\Log\LoggerAwareInterface; |
13
|
|
|
use Psr\Log\LoggerInterface; |
14
|
|
|
use Psr\Log\LogLevel; |
15
|
|
|
use Psr\Log\NullLogger; |
16
|
|
|
use WeakMap; |
17
|
|
|
|
18
|
|
|
use function array_filter; |
19
|
|
|
use function array_map; |
20
|
|
|
use function array_merge; |
21
|
|
|
use function array_sum; |
22
|
|
|
use function assert; |
23
|
|
|
use function count; |
24
|
|
|
use function iterator_to_array; |
25
|
|
|
use function usort; |
26
|
|
|
|
27
|
|
|
/** |
28
|
|
|
* Actual packer. |
29
|
|
|
* @internal |
30
|
|
|
*/ |
31
|
|
|
class WeightRedistributor implements LoggerAwareInterface |
32
|
|
|
{ |
33
|
|
|
private LoggerInterface $logger; |
34
|
|
|
|
35
|
|
|
/** |
36
|
|
|
* @param WeakMap<Box, int> $boxQuantitiesAvailable |
37
|
15 |
|
*/ |
38
|
|
|
public function __construct( |
39
|
|
|
private readonly BoxList $boxes, |
40
|
|
|
private readonly PackedBoxSorter $packedBoxSorter, |
41
|
|
|
private WeakMap $boxQuantitiesAvailable, |
42
|
15 |
|
private readonly ?TimeoutChecker $timeoutChecker, |
43
|
|
|
) { |
44
|
|
|
$this->logger = new NullLogger(); |
45
|
15 |
|
} |
46
|
|
|
|
47
|
15 |
|
public function setLogger(LoggerInterface $logger): void |
48
|
|
|
{ |
49
|
|
|
$this->logger = $logger; |
50
|
|
|
} |
51
|
|
|
|
52
|
|
|
/** |
53
|
15 |
|
* Given a solution set of packed boxes, repack them to achieve optimum weight distribution. |
54
|
|
|
*/ |
55
|
15 |
|
public function redistributeWeight(PackedBoxList $originalBoxes): PackedBoxList |
56
|
15 |
|
{ |
57
|
|
|
$targetWeight = $originalBoxes->getMeanItemWeight(); |
58
|
15 |
|
$this->logger->log(LogLevel::DEBUG, "repacking for weight distribution, weight variance {$originalBoxes->getWeightVariance()}, target weight {$targetWeight}"); |
59
|
|
|
|
60
|
15 |
|
$boxes = iterator_to_array($originalBoxes); |
61
|
|
|
|
62
|
|
|
usort($boxes, static fn (PackedBox $boxA, PackedBox $boxB) => $boxB->getWeight() <=> $boxA->getWeight()); |
63
|
15 |
|
|
64
|
|
|
do { |
65
|
15 |
|
$iterationSuccessful = false; |
66
|
15 |
|
|
67
|
15 |
|
foreach ($boxes as $a => &$boxA) { |
68
|
15 |
|
foreach ($boxes as $b => &$boxB) { |
69
|
|
|
if ($b <= $a || $boxA->getWeight() === $boxB->getWeight()) { |
70
|
|
|
continue; // no need to evaluate |
71
|
11 |
|
} |
72
|
11 |
|
|
73
|
7 |
|
$iterationSuccessful = $this->equaliseWeight($boxA, $boxB, $targetWeight); |
74
|
7 |
|
if ($iterationSuccessful) { |
75
|
|
|
$boxes = array_filter($boxes, static fn (?PackedBox $box) => $box instanceof PackedBox); // remove any now-empty boxes from the list |
76
|
|
|
break 2; |
77
|
|
|
} |
78
|
15 |
|
} |
79
|
|
|
} |
80
|
|
|
} while ($iterationSuccessful); |
81
|
15 |
|
|
82
|
15 |
|
// Combine back into a single list |
83
|
|
|
$packedBoxes = new PackedBoxList($this->packedBoxSorter); |
84
|
15 |
|
$packedBoxes->insertFromArray($boxes); |
85
|
|
|
|
86
|
|
|
return $packedBoxes; |
87
|
|
|
} |
88
|
|
|
|
89
|
|
|
/** |
90
|
|
|
* Attempt to equalise weight distribution between 2 boxes. |
91
|
|
|
* |
92
|
11 |
|
* @return bool was the weight rebalanced? |
93
|
|
|
*/ |
94
|
11 |
|
private function equaliseWeight(PackedBox &$boxA, PackedBox &$boxB, float $targetWeight): bool |
95
|
|
|
{ |
96
|
11 |
|
$anyIterationSuccessful = false; |
97
|
11 |
|
|
98
|
11 |
|
if ($boxA->getWeight() > $boxB->getWeight()) { |
99
|
|
|
$overWeightBox = $boxA; |
100
|
1 |
|
$underWeightBox = $boxB; |
101
|
1 |
|
} else { |
102
|
|
|
$overWeightBox = $boxB; |
103
|
|
|
$underWeightBox = $boxA; |
104
|
11 |
|
} |
105
|
11 |
|
|
106
|
|
|
$overWeightBoxItems = $overWeightBox->items->asItemArray(); |
107
|
11 |
|
$underWeightBoxItems = $underWeightBox->items->asItemArray(); |
108
|
11 |
|
|
109
|
10 |
|
foreach ($overWeightBoxItems as $key => $overWeightItem) { |
110
|
|
|
$this->timeoutChecker?->throwOnTimeout(); |
111
|
|
|
if (!self::wouldRepackActuallyHelp($overWeightBoxItems, $overWeightItem, $underWeightBoxItems, $targetWeight)) { |
112
|
8 |
|
continue; // moving this item would harm more than help |
113
|
8 |
|
} |
114
|
3 |
|
|
115
|
|
|
$newLighterBoxes = $this->doVolumeRepack(array_merge($underWeightBoxItems, [$overWeightItem]), $underWeightBox->box); |
116
|
|
|
if ($newLighterBoxes->count() !== 1) { |
117
|
7 |
|
continue; // only want to move this item if it still fits in a single box |
118
|
|
|
} |
119
|
7 |
|
|
120
|
|
|
$underWeightBoxItems[] = $overWeightItem; |
121
|
|
|
|
122
|
|
|
if (count($overWeightBoxItems) === 1) { // sometimes a repack can be efficient enough to eliminate a box |
123
|
|
|
$boxB = $newLighterBoxes->top(); |
124
|
|
|
$boxA = null; |
125
|
|
|
--$this->boxQuantitiesAvailable[$underWeightBox->box]; |
126
|
|
|
++$this->boxQuantitiesAvailable[$overWeightBox->box]; |
127
|
|
|
|
128
|
7 |
|
return true; |
129
|
7 |
|
} |
130
|
7 |
|
|
131
|
|
|
unset($overWeightBoxItems[$key]); |
132
|
|
|
$newHeavierBoxes = $this->doVolumeRepack($overWeightBoxItems, $overWeightBox->box); |
133
|
|
|
if (count($newHeavierBoxes) !== 1) { |
134
|
|
|
assert(true, 'Could not pack n-1 items into box, even though n were previously in it'); |
135
|
7 |
|
continue; |
136
|
7 |
|
} |
137
|
7 |
|
|
138
|
7 |
|
++$this->boxQuantitiesAvailable[$overWeightBox->box]; |
139
|
7 |
|
++$this->boxQuantitiesAvailable[$underWeightBox->box]; |
140
|
7 |
|
--$this->boxQuantitiesAvailable[$newHeavierBoxes->top()->box]; |
141
|
|
|
--$this->boxQuantitiesAvailable[$newLighterBoxes->top()->box]; |
142
|
7 |
|
$underWeightBox = $boxB = $newLighterBoxes->top(); |
143
|
|
|
$overWeightBox = $boxA = $newHeavierBoxes->top(); |
144
|
|
|
|
145
|
11 |
|
$anyIterationSuccessful = true; |
146
|
|
|
} |
147
|
|
|
|
148
|
|
|
return $anyIterationSuccessful; |
149
|
|
|
} |
150
|
|
|
|
151
|
|
|
/** |
152
|
8 |
|
* Do a volume repack of a set of items. |
153
|
|
|
* @param iterable<Item> $items |
154
|
8 |
|
*/ |
155
|
8 |
|
private function doVolumeRepack(iterable $items, Box $currentBox): PackedBoxList |
156
|
8 |
|
{ |
157
|
8 |
|
$packer = new Packer(); |
158
|
8 |
|
$packer->throwOnUnpackableItem(false); |
159
|
8 |
|
$packer->setLogger($this->logger); |
160
|
|
|
$packer->setBoxes($this->boxes); // use the full set of boxes to allow smaller/larger for full efficiency |
161
|
8 |
|
foreach ($this->boxes as $box) { |
162
|
8 |
|
$packer->setBoxQuantity($box, $this->boxQuantitiesAvailable[$box]); |
163
|
|
|
} |
164
|
8 |
|
$packer->setBoxQuantity($currentBox, $this->boxQuantitiesAvailable[$currentBox] + 1); |
165
|
|
|
$packer->setItems($items); |
166
|
|
|
|
167
|
|
|
return $packer->doBasicPacking(true); |
168
|
|
|
} |
169
|
|
|
|
170
|
|
|
/** |
171
|
|
|
* Not every attempted repack is actually helpful - sometimes moving an item between two otherwise identical |
172
|
|
|
* boxes, or sometimes the box used for the now lighter set of items actually weighs more when empty causing |
173
|
|
|
* an increase in total weight. |
174
|
11 |
|
* @param array<Item> $overWeightBoxItems |
175
|
|
|
* @param array<Item> $underWeightBoxItems |
176
|
11 |
|
*/ |
177
|
11 |
|
private static function wouldRepackActuallyHelp(array $overWeightBoxItems, Item $overWeightItem, array $underWeightBoxItems, float $targetWeight): bool |
178
|
|
|
{ |
179
|
11 |
|
$overWeightItemsWeight = array_sum(array_map(static fn (Item $item) => $item->getWeight(), $overWeightBoxItems)); |
180
|
10 |
|
$underWeightItemsWeight = array_sum(array_map(static fn (Item $item) => $item->getWeight(), $underWeightBoxItems)); |
181
|
|
|
|
182
|
|
|
if ($overWeightItem->getWeight() + $underWeightItemsWeight > $targetWeight) { |
183
|
8 |
|
return false; |
184
|
8 |
|
} |
185
|
|
|
|
186
|
8 |
|
$oldVariance = self::calculateVariance($overWeightItemsWeight, $underWeightItemsWeight); |
|
|
|
|
187
|
|
|
$newVariance = self::calculateVariance($overWeightItemsWeight - $overWeightItem->getWeight(), $underWeightItemsWeight + $overWeightItem->getWeight()); |
188
|
|
|
|
189
|
8 |
|
return $newVariance < $oldVariance; |
190
|
|
|
} |
191
|
8 |
|
|
192
|
|
|
private static function calculateVariance(int $boxAWeight, int $boxBWeight): float |
193
|
|
|
{ |
194
|
|
|
return ($boxAWeight - (($boxAWeight + $boxBWeight) / 2)) ** 2; // don't need to calculate B and ÷ 2, for a 2-item population the difference from mean is the same for each box |
195
|
|
|
} |
196
|
|
|
} |
197
|
|
|
|