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<?php |
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/** |
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* Box packing (3D bin packing, knapsack problem). |
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* |
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* @author Doug Wright |
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*/ |
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namespace DVDoug\BoxPacker; |
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use Psr\Log\LoggerAwareInterface; |
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use Psr\Log\LoggerAwareTrait; |
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use Psr\Log\LogLevel; |
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use Psr\Log\NullLogger; |
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/** |
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* Actual packer. |
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* |
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* @author Doug Wright |
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*/ |
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class WeightRedistributor implements LoggerAwareInterface |
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{ |
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use LoggerAwareTrait; |
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/** |
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* List of box sizes available to pack items into. |
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* |
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* @var BoxList |
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*/ |
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protected $boxes; |
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/** |
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* Constructor. |
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* |
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* @param BoxList $boxList |
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*/ |
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public function __construct(BoxList $boxList) |
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{ |
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$this->boxes = clone $boxList; |
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$this->logger = new NullLogger(); |
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} |
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/** |
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* Given a solution set of packed boxes, repack them to achieve optimum weight distribution. |
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* |
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* @param PackedBoxList $originalBoxes |
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* |
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* @return PackedBoxList |
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*/ |
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public function redistributeWeight(PackedBoxList $originalBoxes) |
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{ |
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$targetWeight = $originalBoxes->getMeanWeight(); |
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$this->logger->log(LogLevel::DEBUG, "repacking for weight distribution, weight variance {$originalBoxes->getWeightVariance()}, target weight {$targetWeight}"); |
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$packedBoxes = new PackedBoxList(); |
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$overWeightBoxes = []; |
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$underWeightBoxes = []; |
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foreach (clone $originalBoxes as $packedBox) { |
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$boxWeight = $packedBox->getWeight(); |
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if ($boxWeight > $targetWeight) { |
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$overWeightBoxes[] = $packedBox; |
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} elseif ($boxWeight < $targetWeight) { |
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$underWeightBoxes[] = $packedBox; |
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} else { |
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$packedBoxes->insert($packedBox); //target weight, so we'll keep these |
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} |
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} |
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do { //Keep moving items from most overweight box to most underweight box |
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$tryRepack = false; |
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$this->logger->log(LogLevel::DEBUG, 'boxes under/over target: '.count($underWeightBoxes).'/'.count($overWeightBoxes)); |
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usort($overWeightBoxes, [$this, 'sortMoreSpaceFirst']); |
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usort($underWeightBoxes, [$this, 'sortMoreSpaceFirst']); |
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foreach ($underWeightBoxes as $u => $underWeightBox) { |
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$this->logger->log(LogLevel::DEBUG, 'Underweight Box '.$u); |
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foreach ($overWeightBoxes as $o => $overWeightBox) { |
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$this->logger->log(LogLevel::DEBUG, 'Overweight Box '.$o); |
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$overWeightBoxItems = $overWeightBox->getItems()->asArray(); |
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//For each item in the heavier box, try and move it to the lighter one |
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/** @var Item $overWeightBoxItem */ |
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foreach ($overWeightBoxItems as $oi => $overWeightBoxItem) { |
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$this->logger->log(LogLevel::DEBUG, 'Overweight Item '.$oi); |
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if ($underWeightBox->getWeight() + $overWeightBoxItem->getWeight() > $targetWeight) { |
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$this->logger->log(LogLevel::DEBUG, 'Skipping item for hindering weight distribution'); |
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continue; //skip if moving this item would hinder rather than help weight distribution |
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} |
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$newItemsForLighterBox = $underWeightBox->getItems()->asArray(); |
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$newItemsForLighterBox[] = $overWeightBoxItem; |
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$newLighterBoxPacker = new Packer(); //we may need a bigger box |
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$newLighterBoxPacker->setBoxes($this->boxes); |
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$newLighterBoxPacker->setItems($newItemsForLighterBox); |
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$this->logger->log(LogLevel::INFO, '[ATTEMPTING TO PACK LIGHTER BOX]'); |
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$newLighterBox = $newLighterBoxPacker->doVolumePacking()->top(); |
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if ($newLighterBox->getItems()->count() === count($newItemsForLighterBox)) { //new item fits |
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$this->logger->log(LogLevel::DEBUG, 'New item fits'); |
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unset($overWeightBoxItems[$oi]); //now packed in different box |
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if (count($overWeightBoxItems) > 0) { |
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$newHeavierBoxPacker = new Packer(); //we may be able to use a smaller box |
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$newHeavierBoxPacker->setBoxes($this->boxes); |
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$newHeavierBoxPacker->setItems($overWeightBoxItems); |
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$this->logger->log(LogLevel::INFO, '[ATTEMPTING TO PACK HEAVIER BOX]'); |
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$newHeavierBoxes = $newHeavierBoxPacker->doVolumePacking(); |
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if ($newHeavierBoxes->count() |
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> 1) { //found an edge case in packing algorithm that *increased* box count |
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$this->logger->log( |
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LogLevel::INFO, |
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'[REDISTRIBUTING WEIGHT] Abandoning redistribution, because new packing is less efficient than original' |
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); |
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return $originalBoxes; |
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} |
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$overWeightBoxes[$o] = $newHeavierBoxes->top(); |
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} else { |
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unset($overWeightBoxes[$o]); |
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} |
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$underWeightBoxes[$u] = $newLighterBox; |
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$tryRepack = true; //we did some work, so see if we can do even better |
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break 3; |
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} |
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} |
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} |
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} |
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} while ($tryRepack); |
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//Combine back into a single list |
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$packedBoxes->insertFromArray($overWeightBoxes); |
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$packedBoxes->insertFromArray($underWeightBoxes); |
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return $packedBoxes; |
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} |
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/** |
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* @param PackedBox $boxA |
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* @param PackedBox $boxB |
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* |
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* @return int |
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*/ |
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private function sortMoreSpaceFirst(PackedBox $boxA, PackedBox $boxB) |
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{ |
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$choice = $boxB->getItems()->count() - $boxA->getItems()->count(); |
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if ($choice === 0) { |
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$choice = $boxA->getInnerVolume() - $boxB->getInnerVolume(); |
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} |
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if ($choice === 0) { |
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$choice = $boxB->getWeight() - $boxA->getWeight(); |
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} |
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return $choice; |
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} |
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} |
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dvdoug /
BoxPacker
