|
1
|
|
|
<?php |
|
2
|
|
|
/** |
|
3
|
|
|
* Box packing (3D bin packing, knapsack problem). |
|
4
|
|
|
* |
|
5
|
|
|
* @author Doug Wright |
|
6
|
|
|
*/ |
|
7
|
|
|
declare(strict_types=1); |
|
8
|
|
|
|
|
9
|
|
|
namespace DVDoug\BoxPacker; |
|
10
|
|
|
|
|
11
|
|
|
use Psr\Log\LoggerAwareInterface; |
|
12
|
|
|
use Psr\Log\LoggerInterface; |
|
13
|
|
|
use Psr\Log\LogLevel; |
|
14
|
|
|
use Psr\Log\NullLogger; |
|
15
|
|
|
use SplObjectStorage; |
|
16
|
|
|
|
|
17
|
|
|
use function array_filter; |
|
18
|
|
|
use function array_map; |
|
19
|
|
|
use function array_merge; |
|
20
|
|
|
use function array_sum; |
|
21
|
|
|
use function count; |
|
22
|
|
|
use function iterator_to_array; |
|
23
|
|
|
use function usort; |
|
24
|
|
|
|
|
25
|
|
|
/** |
|
26
|
|
|
* Actual packer. |
|
27
|
|
|
* |
|
28
|
|
|
* @internal |
|
29
|
|
|
*/ |
|
30
|
|
|
class WeightRedistributor implements LoggerAwareInterface |
|
31
|
|
|
{ |
|
32
|
|
|
private LoggerInterface $logger; |
|
33
|
|
|
|
|
34
|
|
|
private BoxList $boxes; |
|
35
|
|
|
|
|
36
|
|
|
/** |
|
37
|
|
|
* @var SplObjectStorage<Box, int> |
|
38
|
|
|
*/ |
|
39
|
|
|
private SplObjectStorage $boxQuantitiesAvailable; |
|
40
|
|
|
|
|
41
|
|
|
private PackedBoxSorter $packedBoxSorter; |
|
42
|
|
|
|
|
43
|
|
|
public function __construct(BoxList $boxList, PackedBoxSorter $packedBoxSorter, SplObjectStorage $boxQuantitiesAvailable) |
|
44
|
|
|
{ |
|
45
|
|
|
$this->boxes = $boxList; |
|
46
|
|
|
$this->packedBoxSorter = $packedBoxSorter; |
|
47
|
|
|
$this->boxQuantitiesAvailable = $boxQuantitiesAvailable; |
|
48
|
|
|
$this->logger = new NullLogger(); |
|
49
|
|
|
} |
|
50
|
|
|
|
|
51
|
|
|
public function setLogger(LoggerInterface $logger): void |
|
52
|
|
|
{ |
|
53
|
|
|
$this->logger = $logger; |
|
54
|
|
|
} |
|
55
|
|
|
|
|
56
|
|
|
/** |
|
57
|
15 |
|
* Given a solution set of packed boxes, repack them to achieve optimum weight distribution. |
|
58
|
|
|
*/ |
|
59
|
15 |
|
public function redistributeWeight(PackedBoxList $originalBoxes): PackedBoxList |
|
60
|
15 |
|
{ |
|
61
|
15 |
|
$targetWeight = $originalBoxes->getMeanItemWeight(); |
|
62
|
15 |
|
$this->logger->log(LogLevel::DEBUG, "repacking for weight distribution, weight variance {$originalBoxes->getWeightVariance()}, target weight {$targetWeight}"); |
|
63
|
|
|
|
|
64
|
|
|
/** @var PackedBox[] $boxes */ |
|
65
|
|
|
$boxes = iterator_to_array($originalBoxes); |
|
66
|
|
|
|
|
67
|
|
|
usort($boxes, static fn (PackedBox $boxA, PackedBox $boxB) => $boxB->getWeight() <=> $boxA->getWeight()); |
|
68
|
15 |
|
|
|
69
|
|
|
do { |
|
70
|
15 |
|
$iterationSuccessful = false; |
|
71
|
15 |
|
|
|
72
|
|
|
foreach ($boxes as $a => &$boxA) { |
|
73
|
|
|
foreach ($boxes as $b => &$boxB) { |
|
74
|
15 |
|
if ($b <= $a || $boxA->getWeight() === $boxB->getWeight()) { |
|
75
|
|
|
continue; // no need to evaluate |
|
76
|
15 |
|
} |
|
77
|
15 |
|
|
|
78
|
15 |
|
$iterationSuccessful = $this->equaliseWeight($boxA, $boxB, $targetWeight); |
|
79
|
|
|
if ($iterationSuccessful) { |
|
80
|
|
|
$boxes = array_filter($boxes, static fn (?PackedBox $box) => $box instanceof PackedBox); // remove any now-empty boxes from the list |
|
81
|
15 |
|
break 2; |
|
82
|
|
|
} |
|
83
|
15 |
|
} |
|
84
|
15 |
|
} |
|
85
|
15 |
|
} while ($iterationSuccessful); |
|
86
|
15 |
|
|
|
87
|
|
|
// Combine back into a single list |
|
88
|
|
|
$packedBoxes = new PackedBoxList($this->packedBoxSorter); |
|
89
|
10 |
|
$packedBoxes->insertFromArray($boxes); |
|
90
|
10 |
|
|
|
91
|
5 |
|
return $packedBoxes; |
|
92
|
5 |
|
} |
|
93
|
5 |
|
|
|
94
|
5 |
|
/** |
|
95
|
|
|
* Attempt to equalise weight distribution between 2 boxes. |
|
96
|
|
|
* |
|
97
|
|
|
* @return bool was the weight rebalanced? |
|
98
|
15 |
|
*/ |
|
99
|
|
|
private function equaliseWeight(PackedBox &$boxA, PackedBox &$boxB, float $targetWeight): bool |
|
100
|
|
|
{ |
|
101
|
15 |
|
$anyIterationSuccessful = false; |
|
102
|
15 |
|
|
|
103
|
|
|
if ($boxA->getWeight() > $boxB->getWeight()) { |
|
104
|
15 |
|
$overWeightBox = $boxA; |
|
105
|
|
|
$underWeightBox = $boxB; |
|
106
|
|
|
} else { |
|
107
|
|
|
$overWeightBox = $boxB; |
|
108
|
|
|
$underWeightBox = $boxA; |
|
109
|
|
|
} |
|
110
|
|
|
|
|
111
|
|
|
$overWeightBoxItems = $overWeightBox->getItems()->asItemArray(); |
|
112
|
10 |
|
$underWeightBoxItems = $underWeightBox->getItems()->asItemArray(); |
|
113
|
|
|
|
|
114
|
10 |
|
foreach ($overWeightBoxItems as $key => $overWeightItem) { |
|
115
|
|
|
if (!self::wouldRepackActuallyHelp($overWeightBoxItems, $overWeightItem, $underWeightBoxItems, $targetWeight)) { |
|
116
|
10 |
|
continue; // moving this item would harm more than help |
|
117
|
10 |
|
} |
|
118
|
10 |
|
|
|
119
|
|
|
$newLighterBoxes = $this->doVolumeRepack(array_merge($underWeightBoxItems, [$overWeightItem]), $underWeightBox->getBox()); |
|
120
|
1 |
|
if ($newLighterBoxes->count() !== 1) { |
|
121
|
1 |
|
continue; // only want to move this item if it still fits in a single box |
|
122
|
|
|
} |
|
123
|
|
|
|
|
124
|
10 |
|
$underWeightBoxItems[] = $overWeightItem; |
|
125
|
10 |
|
|
|
126
|
|
|
if (count($overWeightBoxItems) === 1) { // sometimes a repack can be efficient enough to eliminate a box |
|
127
|
10 |
|
$boxB = $newLighterBoxes->top(); |
|
128
|
10 |
|
$boxA = null; |
|
129
|
8 |
|
$this->boxQuantitiesAvailable[$underWeightBox->getBox()] = $this->boxQuantitiesAvailable[$underWeightBox->getBox()] - 1; |
|
130
|
|
|
$this->boxQuantitiesAvailable[$overWeightBox->getBox()] = $this->boxQuantitiesAvailable[$overWeightBox->getBox()] + 1; |
|
131
|
|
|
|
|
132
|
7 |
|
return true; |
|
133
|
7 |
|
} |
|
134
|
2 |
|
|
|
135
|
|
|
unset($overWeightBoxItems[$key]); |
|
136
|
|
|
$newHeavierBoxes = $this->doVolumeRepack($overWeightBoxItems, $overWeightBox->getBox()); |
|
137
|
5 |
|
if (count($newHeavierBoxes) !== 1) { |
|
138
|
|
|
continue; // this should never happen, if we can pack n+1 into the box, we should be able to pack n |
|
139
|
5 |
|
} |
|
140
|
|
|
|
|
141
|
|
|
$this->boxQuantitiesAvailable[$overWeightBox->getBox()] = $this->boxQuantitiesAvailable[$overWeightBox->getBox()] + 1; |
|
142
|
|
|
$this->boxQuantitiesAvailable[$underWeightBox->getBox()] = $this->boxQuantitiesAvailable[$underWeightBox->getBox()] + 1; |
|
143
|
|
|
$this->boxQuantitiesAvailable[$newHeavierBoxes->top()->getBox()] = $this->boxQuantitiesAvailable[$newHeavierBoxes->top()->getBox()] - 1; |
|
144
|
|
|
$this->boxQuantitiesAvailable[$newLighterBoxes->top()->getBox()] = $this->boxQuantitiesAvailable[$newLighterBoxes->top()->getBox()] - 1; |
|
145
|
|
|
$underWeightBox = $boxB = $newLighterBoxes->top(); |
|
146
|
|
|
$overWeightBox = $boxA = $newHeavierBoxes->top(); |
|
147
|
|
|
|
|
148
|
5 |
|
$anyIterationSuccessful = true; |
|
149
|
5 |
|
} |
|
150
|
5 |
|
|
|
151
|
|
|
return $anyIterationSuccessful; |
|
152
|
|
|
} |
|
153
|
|
|
|
|
154
|
5 |
|
/** |
|
155
|
5 |
|
* Do a volume repack of a set of items. |
|
156
|
5 |
|
* @param iterable<Item> $items |
|
157
|
5 |
|
*/ |
|
158
|
5 |
|
private function doVolumeRepack(iterable $items, Box $currentBox): PackedBoxList |
|
159
|
5 |
|
{ |
|
160
|
|
|
$packer = new Packer(); |
|
161
|
5 |
|
$packer->setLogger($this->logger); |
|
162
|
|
|
$packer->setBoxes($this->boxes); // use the full set of boxes to allow smaller/larger for full efficiency |
|
163
|
|
|
foreach ($this->boxes as $box) { |
|
164
|
10 |
|
$packer->setBoxQuantity($box, $this->boxQuantitiesAvailable[$box]); |
|
165
|
|
|
} |
|
166
|
|
|
$packer->setBoxQuantity($currentBox, $this->boxQuantitiesAvailable[$currentBox] + 1); |
|
167
|
|
|
$packer->setItems($items); |
|
168
|
|
|
|
|
169
|
|
|
return $packer->doVolumePacking(true, true); |
|
170
|
7 |
|
} |
|
171
|
|
|
|
|
172
|
7 |
|
/** |
|
173
|
7 |
|
* Not every attempted repack is actually helpful - sometimes moving an item between two otherwise identical |
|
174
|
7 |
|
* boxes, or sometimes the box used for the now lighter set of items actually weighs more when empty causing |
|
175
|
7 |
|
* an increase in total weight. |
|
176
|
7 |
|
* @param array<Item> $overWeightBoxItems |
|
177
|
|
|
* @param array<Item> $underWeightBoxItems |
|
178
|
7 |
|
*/ |
|
179
|
7 |
|
private static function wouldRepackActuallyHelp(array $overWeightBoxItems, Item $overWeightItem, array $underWeightBoxItems, float $targetWeight): bool |
|
180
|
|
|
{ |
|
181
|
7 |
|
$overWeightItemsWeight = array_sum(array_map(static fn (Item $item) => $item->getWeight(), $overWeightBoxItems)); |
|
182
|
|
|
$underWeightItemsWeight = array_sum(array_map(static fn (Item $item) => $item->getWeight(), $underWeightBoxItems)); |
|
183
|
|
|
|
|
184
|
|
|
if ($overWeightItem->getWeight() + $underWeightItemsWeight > $targetWeight) { |
|
185
|
|
|
return false; |
|
186
|
|
|
} |
|
187
|
|
|
|
|
188
|
|
|
$oldVariance = self::calculateVariance($overWeightItemsWeight, $underWeightItemsWeight); |
|
|
|
|
|
|
189
|
10 |
|
$newVariance = self::calculateVariance($overWeightItemsWeight - $overWeightItem->getWeight(), $underWeightItemsWeight + $overWeightItem->getWeight()); |
|
190
|
|
|
|
|
191
|
10 |
|
return $newVariance < $oldVariance; |
|
192
|
10 |
|
} |
|
193
|
|
|
|
|
194
|
10 |
|
private static function calculateVariance(int $boxAWeight, int $boxBWeight): float |
|
195
|
8 |
|
{ |
|
196
|
|
|
return ($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 |
|
197
|
|
|
} |
|
198
|
|
|
} |
|
199
|
|
|
|
dvdoug /
BoxPacker
Loading history...